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Survival Probability (survival + probability)
Kinds of Survival Probability Selected AbstractsSurvival of individuals with cerebral palsy receiving continuous intrathecal baclofen treatment: a matched-cohort studyDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 7 2010LINDA E KRACH Aim, To determine whether intrathecal baclofen (ITB) changes mortality risk in persons with cerebral palsy (CP). Method, Records were reviewed for all persons with CP who were managed with ITB for hypertonicity at a specialty hospital in Minnesota between May 1993 and August 2007. A comparison cohort was randomly selected from clients of the California Department of Developmental Services who were initially evaluated between 1987 and 1990 and were matched to those with ITB for age, sex, Gross Motor Function Classification System (GMFCS) level, presence or absence of epilepsy, and feeding-tube use. Survival probabilities were estimated using the Kaplan,Meier method, and differences were tested via log-rank. Results, Three hundred and fifty-nine persons with CP (202 males, 157 females) receiving ITB for hypertonicity (mean age 12y 8mo, SD 7y 9mo, range 3y 1mo to 39y 9mo) were matched to 349 persons without ITB pumps (195 males, 154 females; mean age 12y 7mo, SD 8y 4mo, range 2y 7mo to 40y). The proportion of patients at different GMFCS levels in the ITB and in the non-ITB cohorts, respectively, was as follows: level II 3% and 3%, level III 16% and 16%, level IV 38% and 37%, and level V 43% and 44%. Survival at 8 years of follow-up was 92% (SD 1.9%) in the ITB cohort and 82% (SD 2.4%) in the non-ITB cohort (p<0.001). After adjustment to account for recent trends in improved survival in CP, 8-year survival in the non-ITB cohort was 88%, which was not significantly different from the ITB cohort (p=0.073). Interpretation, ITB therapy does not increase mortality in individuals with CP and may suggest an increase in life expectancy. [source] Survival analysis for degree of compliance with supportive periodontal therapyJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 12 2001M. Ojima Abstract Background, aims: The purpose of this investigation was to evaluate the degree of compliance for supportive periodontal therapy (SPT) and to determine factors in relation to patients who failed to continue SPT programs. Method: A sample of 1896 patients who were treated between 1988 and 1999 was studied. The patients were classified by gender, age group and the distance between their house and the hospital. The number of visits was counted based on an electronic patient record for SPT. Data were analyzed by survival analysis. Survival probabilities in SPT were estimated by the Kaplan-Meier method and compared by the generalized Wilcoxon test. Results: 28% of patients did not comply with the first visit for SPT. The older patients had higher tendencies to continue the SPT program than the younger patients. No significant differences in compliance were found between males and females or between short-distance and long-distance groups. However, when these factors were adjusted by age, significantly different patterns were shown on the curves of survival probability: in males, significant differences were found between the 20 s and 30 s (p<0.00001) and between the 50 s and 60 s (p<0.01). In females, significant differences were found between the 40 s and 50 s (p<0.001) and between the 60 s and 70 s (p<0.001). The differences of the survival probability by age group were greater in the short-distance group than in the long-distance group. Conclusions: The results suggest that age is the most important factor for compliance of the patients with SPT, not only alone but also in relation to the other factors. Zusammenfassung Ziel: Der Zweck dieser Untersuchung war es, das Ausmaß der Compliance bei perodontaler Erhaltungstherapie (SPT) zu evaluieren und Patienten bezogene Faktoren zu bestimmen, wenn diese das SPT-Programm nicht forsetzten. Material und Methoden: Eine Stichprobe von 1896 Patienten, welche zwischen 1988 und 1999 behandelt wurden nahm man in die Studie auf. Die Patienten wurden klassifiziert nach Geschlecht, Altersgruppe und der Entfernung zwischen ihrem Haus und der Klinik. Auf der Grundlage einer elektronischen Patientenakte wurde die Anzahl der Sitzungen errechnet. Die Daten wurden mittels Überlebensanalyse ausgewertet. Die Überlebenswahrscheinlichkeiten in der SPT wurde mit der Kaplan-Meier-Methode geschätzt und mit dem allgemeinen Wilkoxon-Test verglichen. Ergebnisse: 28% der Patienten zeigten keine Compliance mit dem ersten Termin für die SPT. Die älteren Patienten zeigten eine stärkere Tendenz zur Forsetzung des SPT-Programms als die jüngeren Patienten. Zwischen Männern und Frauen oder den Gruppen mit geringer und größerer Entfernung gab es keine Unterschiede in der Compliance. Wenn diese Faktoren bezüglich des Alters adjustiert wurden, konnten signifikant unterschiedliche Muster bei den Kurven für die Überlebenswahrscheinlichkeit gezeigt werden: bei den Männern fand man signifikante Unterschiede zwischen der 20er und 30er-Gruppe (p<0.00001) und zwischen der 50er und 60er-Gruppe (p<0.01). Bei den Frauen fand man signifikante Unterschiede zwischen der 40er und 50er-Gruppe (p<0.001) und zwischen der 60er und 70er-Gruppe (p<0.001). Die Unterschiede der Überlebenswahrscheinlichkeit der Altersgruppen waren in der Gruppe mit geringen Entfernung größer, als in der Gruppe mit größerer Entfernung. Schlussfolgerung: Die Ergebnisse lassen annehmen, dass das Alter der wichtigste Faktor für die Compliance der Patienten mit der SPT ist. Dies gilt nicht nur für das Alter als alleinigen Faktor sondern auch zusammen mit den anderen Faktoren. Résumé But: Le but de cette étude était d'évaluer le degré de coopération pour la thérapeutique parodontale de soutien (SPT) et de déterminer les facteurs en cause relatifs aux patients qui ne suivaient pas le programme de STP. Matériaux et méthodes: Un échantillon de 1896 patients qui furent traités entre 1988 et 1999 a étéétudié. Les patieants ont été classés par sexe, âge et distance entre leur habitation et l'hôpital. Le nombre de visite était quantifiéélectroniquement pour la STP. Les données étaient analysées par analyse de continuité. Les probabilitiés de continuité de la STP étaient estimées par la méthode de Kaplan-Meyer et comparées par le test de Wilcoxon généralisé. Résultats: 28% des patients ne coopéraient pas pour la première visite de maintenance. Les patients les plus âgés avaient une plus forte tendance à suivre leur programme de STP que les plus jeunes. Aucune différence significative pour la maintenance n'était observée entre les hommes et les femmes et pour la distance entre l'habitation et l'hôpital. Cependant, lorsque l'on ajustait ces facteurs pour l'âge, différences caractéristiques des courbes de probabilités de continuitéétaient observées: chez les hommes, des différences significatives existatient entre les groupes d'âges 20 et 30 ans (p<0.00001) et entre les groupes d'âge 50 et 60 ans (p<0.001). Chez les femmes, ces différences existaient entre les groupes d'âge 40 et 50 ans (p<0.001) et 60 et 70 ans (p<0.001). Les différences de la probabilité de continuité par groupe d'âge étaient plus grandes dans le groupe résidant près de l'hôpital que pour les patients habitant loin. Conclusion: Les résultats suggèrent que l'âge est le facteur le plus important pour la coopération des patients envers leurs SPT, non seulement seul mais aussi en relation avec les autres facteurs. [source] Predictive models of short- and long-term survival in patients with nonbiliary cirrhosisLIVER TRANSPLANTATION, Issue 3 2003Gérald Longheval The limited number of donor organs has placed a burden on the medical community to improve patient selection and timing of liver transplantation (LT). We aim to evaluate short- and long-term survival of 124 consecutive patients with a diagnosis of nonbiliary cirrhosis. Seventeen clinical, biochemical, functional, and hemodynamic parameters were computed. Patient survival was evaluated in the short term (3 months) by logistic regression, and the predictive power of the model was evaluated using receiver operating characteristic curves and the log likelihood ratio. For the long-term (up to 5 years) prognosis, the Cox proportional model was used. During follow-up, 54 patients died and 20 patients underwent LT. In the short-term study, the Model for End-Stage Liver Disease score (including bilirubin level, international normalized ratio [INR], and creatinine level) was as predictive as our score, which contained only two independent indicators (bilirubin and creatinine levels). In the long-term study, three independent variables (albumin level, INR, and creatinine level) emerged from the Cox model, and patients were classified into three survival-risk groups according to a prognostic index (PI): ,1.039 × albumin (grams per deciliter) + 1.909 × loge INR + 1.207 × loge serum creatinine (milligrams per deciliter). Survival probabilities at 1 and 5 years were 89% and 80%, 63% and 52%, and 23% and 10% with a low, medium, and high PI, respectively. The validation study using the split-sample technique and data from independent patients confirmed that a high PI (>,2.5) identifies patients with a poor prognosis within 5 years. We thus have shown and validated that risk for death at the short and long term of patients with nonbiliary cirrhosis can be predicted with great accuracy using models containing a few simple and easily obtained objective variables, and these survival models are useful tools in clinical decision making, especially in deciding to list patients for LT and prioritization on the liver waiting list. [source] Capture,recapture models with heterogeneity to study survival senescence in the wildOIKOS, Issue 3 2010Guillaume Péron Detecting senescence in wild populations and estimating its strength raise three challenges. First, in the presence of individual heterogeneity in survival probability, the proportion of high-survival individuals increases with age. This increase can mask a senescence-related decrease in survival probability when the probability is estimated at the population level. To accommodate individual heterogeneity we use a mixture model structure (discrete classes of individuals). Second, the study individuals can elude the observers in the field, and their detection rate can be heterogeneous. To account for detectability issues we use capture,mark,recapture (CMR) methodology, mixture models and data that provide information on individuals' detectability. Last, emigration to non-monitored sites can bias survival estimates, because it can occur at the end of the individuals' histories and mimic earlier death. To model emigration we use Markovian transitions to and from an unobservable state. These different model structures are merged together using hidden Markov chain CMR models, or multievent models. Simulation studies illustrate that reliable evidence for survival senescence can be obtained using highly heterogeneous data from non site-faithful individuals. We then design a tailored application for a dataset from a colony of black-headed gull Chroicocephalus ridibundus. Survival probabilities do not appear individually variable, but evidence for survival senescence becomes significant only when accounting for other sources of heterogeneity. This result suggests that not accounting for heterogeneity leads to flawed inference and/or that emigration heterogeneity mimics survival heterogeneity and biases senescence estimates. [source] Survival probability of zirconia-based fixed dental prostheses up to 5 yr: a systematic review of the literatureEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 5 2010Jaana-Sophia Schley Schley J-S, Heussen N, Reich S, Fischer J, Haselhuhn K, Wolfart S. Survival probability of zirconia-based fixed dental prostheses up to 5 yr: a systematic review of the literature. Eur J Oral Sci 2010; 118: 443,450. © 2010 Eur J Oral Sci The purpose of this systematic review was to calculate the 5-yr survival rates of all-ceramic zirconia-based fixed dental prostheses (FDPs) and to analyze technical and biological complications. An electronic literature search of MEDLINE (PubMed) was conducted independently by three reviewers to identify clinical studies from 1999 to 2009 and was completed by a manual search. Keywords and inclusion and exclusion criteria were well-defined. The search revealed 399 titles and led to the final analysis of 18 full-text articles. Nine studies met the inclusion criteria. Extracted data were statistically calculated into 5-yr survival rates and 5-yr complication-free rates by using Poisson regression analysis. In total, 310, 3- to 4-unit FDPs and 20 FDPs with more than 4 units were included. The estimated 5-yr survival rate for all FDPs was 94.29% (95% CI: 58.98,99.32); 19 FDPs were lost as a result of catastrophic failures. The 5-yr complication-free rate regarding technical complications was 76.41% (95% CI: 42.42,91.60) with chipping being the most frequent complication. Regarding biological complications, the 5-yr complication-free rate was 91.72% (95% CI: 59.19,98.53). The survival rates of zirconia-based short-unit FDPs are promising. However, an important improvement of the veneering systems is required, and for FDPs with more units in function, further randomized, controlled clinical trials are necessary. [source] Impact of injecting drug use on mortality in Danish HIV-infected patients: a nation-wide population-based cohort studyADDICTION, Issue 3 2010Mette V. Larsen ABSTRACT Objectives To estimate the impact of injecting drug use (IDU) on mortality in HIV-infected patients in the highly active antiretroviral therapy (HAART) era. Design Population-based, nation-wide prospective cohort study in Denmark (the Danish HIV Cohort Study). Methods A total of 4578 HIV-infected patients were followed from 1 January 1997 or date of HIV diagnosis. We calculated mortality rates stratified on IDU. One-, 5- and 10-year survival probabilities were estimated by Kaplan,Meier methods, and Cox regression analyses were used to estimate mortality rate ratios (MRR). Results Of the patients, 484 (10.6%) were categorized as IDUs and 4094 (89.4%) as non-IDUs. IDUs were more likely to be women, Caucasian, hepatitis C virus (HCV) co-infected and younger at baseline; 753 patients died during observation (206 IDUs and 547 non-IDUs). The estimated 10-year survival probabilities were 53.2% [95% confidence interval (CI): 48.1,58.3] in the IDU group and 82.1% (95% CI: 80.7,83.6) in the non-IDU group. IDU as route of HIV infection more than tripled the mortality in HIV-infected patients (MRR: 3.2; 95% CI: 2.7,3.8). Adjusting for potential confounders did not change this estimate substantially. The risk of HIV-related death was not increased in IDUs compared to non-IDUs (MRR 1.1; 95% CI 0.7,1.7). Conclusions Although Denmark's health care system is tax paid and antiretroviral therapy is provided free of charge, HIV-infected IDUs still suffer from substantially increased mortality in the HAART era. The increased risk of death seems to be non-HIV-related and is due probably to the well-known risk factors associated with intravenous drug abuse. [source] Statistical tests and power analysis for three in-vivo bioassays to determine the quality of marine sedimentsENVIRONMETRICS, Issue 3 2002Nelly van der Hoeven Abstract Statistical tests are recommended for three marine sediment in-vivo bioassays. In two bioassays (Corophium volutator and Echinocardium cordatum), the mortality in the sediment is compared with that in a control. An unconditional 2,×,2 test is recommended. For one bioassay (Rotoxkit MTM with Brachionus plicatilis), mortality in a dilution series of pore water is compared with the mortality in a control. The Williams test for trends is recommended. For each of these tests the power to assess an effect has been calculated. The number of replicates recommended in the standardized test protocol only allows large effects to be observed in almost all (95 per cent) of the experiments. Given the control mortality rates estimated from a large set of controls, a power of 95 per cent will only be reached if the mortality rate in the tested sediment is over 30 per cent for C. volutator and almost 60 per cent for E. cordatum. To reach this power for bioassays with B. plicatilis, where five concentrations are compared with a control, the mortality rate in the lowest effect concentration should be about 35 per cent. As an alternative to no effect testing, it is suggested that whether the effect of a treatment remains below some chosen minimal relevant effect (MRE) should be tested. Given an MRE at a fixed mortality rate of 25 per cent and ,,=,0.05, at least 55 individuals are necessary to be reasonably sure (95 per cent) that a mortality of 10 per cent will not be declared toxic incorrectly. The tests for mortality are based on the assumption that the survival probabilities of individuals within a test vessel are independent. We have described a method to test this assumption and applied it to the data on C. volutator. Copyright © 2002 John Wiley & Sons, Ltd. [source] Results of the PETHEMA ALL-96 trial in elderly patients with Philadelphia chromosome-negative acute lymphoblastic leukemiaEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 2 2007Juan-Manuel Sancho Abstract Background and aim:,Only 20,30% of elderly patients with acute lymphoblastic leukemia (ALL) are enrolled in clinical trials because of co-morbid disorders or poor performance status. We present the results of treatment of Philadelphia chromosome-negative (Ph,) ALL patients over 55 yr treated in the PETHEMA ALL-96 trial. Patients and methods:,From 1996 to 2006, 33 patients 55 yr with Ph, ALL were included. Induction therapy was vincristine, daunorubicin, prednisone, asparaginase, and cyclophosphamide over 5 weeks. Central nervous system (CNS) prophylaxis involved triple intrathecal (IT) therapy, 14 doses over the first year. Consolidation-1 included mercaptopurine, methotrexate, teniposide and cytarabine, followed by one consolidation-2 cycle similar to the induction cycle. Maintenance consisted of mercaptopurine and methotrexate up to 2 yr in complete remission (CR) with monthly reinduction cycles (vincristine, prednisone and asparaginase) during the first year. Results:,Median (range) age was 65 yr (56,77). Phenotype (30 patients): early-pre-B 7, common/pre-B 18, T 5. Cytogenetics (28 patients): normal 12, complex 10, t(4;11) 2 and other 4. CR was achieved in 19/33 (57.6%) patients, early death occurred in 12 (36.4%) and 2 (6%) were resistant. Overall survival and disease-free survival probabilities (2 yr, 95% CI) were 39% (21%,57%) and 46% (22%,70%), respectively (median follow up of 24 months). Removal of asparaginase and cyclophosphamide from the induction decreased induction death (OR 0.119, CI 95% 0.022,0.637, P = 0.013) and increased survival (20% vs. 52%, P = 0.05). Conclusions:,The prognosis of elderly Ph, ALL patients is poor. In this study, less intensive induction decreased toxic death, allowing delivery of planned consolidation therapy and increased survival probability. [source] Prediction of survival in patients with head and neck cancerHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 9 2001Robert Jan Baatenburg de Jong PhD Abstract Background In patients with head and neck squamous cell carcinoma (HNSCC) the estimated prognosis is usually based on the TNM classification. The relative weight of the three contributing parameters is often not completely clear. Moreover, the impact of other important clinical variables such as age, gender, prior malignancies, etc is very difficult to substantiate in daily clinical practice. The Cox-regression model allows us to estimate the effect of different variables simultaneously. The purpose of this study was to design a model for application in new HNSCC patients. In our historical data-base of patients with HNSCC, patient, treatment, and follow-up data are stored by trained oncological data managers. With these hospital-based data, we developed a statistical model for risk assessment and prediction of overall survival. This model serves in clinical decision making and appropriate counseling of patients with HNSCC. Patients and Methods All patients with HNSCC of the oral cavity, the pharynx, and the larynx diagnosed in our hospital between 1981 and 1998 were included. In these 1396 patients, the prognostic value of site of the primary tumor, age at diagnosis, gender, T-, N-, and M-stage, and prior malignancies were studied univariately by Kaplan-Meier curves and the log-rank test. The Cox-regression model was used to investigate the effect of these variables simultaneously on overall survival and to develop a prediction model for individual patients. Results In the univariate analyses, all variables except gender contributed significantly to overall survival. Their contribution remained significant in the multivariate Cox model. Based on the relative risks and the baseline survival curve, the expected survival for a new HNSCC patient can be calculated. Conclusions It is possible to predict survival probabilities in a new patient with HNSCC based on historical results from a data-set analyzed with the Cox-regression model. The model is supplied with hospital-based data. Our model can be extended by other prognostic factors such as co-morbidity, histological data, molecular biology markers, etc. The results of the Cox-regression may be used in patient counseling, clinical decision making, and quality maintenance. © 2001 John Wiley & Sons, Inc. Head Neck 23: 718,724, 2001. [source] The impact of detection and treatment on lifetime medical costs for patients with precancerous polyps and colorectal cancerHEALTH ECONOMICS, Issue 12 2009David H. Howard Abstract Understanding the costs associated with early detection of disease is important for determining the fiscal implications of government-funded screening programs. We estimate the lifetime medical costs for patients with screen-detected versus undetected polyps and early-stage colorectal cancer. Typically, cost,effectiveness studies of screening account only for the direct costs of screening and cancer care. Our estimates include costs for unrelated conditions. We applied the Kaplan,Meier Smoothing Estimator to estimate lifetime costs for beneficiaries with screen-detected polyps and cancer. Phase-specific costs and survival probabilities were calculated from the Surveillance, Epidemiology, and End Results-Medicare database for Medicare beneficiaries aged ,65. We estimate costs from the point of detection onward; therefore, our results do not include the costs associated with screening. We used a modified version of the model to estimate what lifetime costs for these patients would have been if the polyps or cancer remained undetected, based on assumptions about the ,lead time' for polyps and early-stage cancer. For younger patients, polyp removal is cost saving. Treatment of early-stage cancer is cost increasing. Copyright © 2009 John Wiley & Sons, Ltd. [source] Infant mortality and child nutrition in BangladeshHEALTH ECONOMICS, Issue 9 2008Diane Dancer Abstract The excess female infant mortality observed in South Asia has typically been attributed to gender discrimination in the intra-household allocation of food and medical care. However, studies on child nutrition find no evidence of gender differences. A natural explanation could be that in environments of high infant mortality of females, the surviving children are healthier, so that child nutrition cannot be studied independently of mortality. In this paper, we use data from the 2004 Bangladesh Demographic Health Survey to investigate if there are any gender differences in survival probabilities and whether this leads to differences in child nutrition. We argue the importance of establishing whether or not there exists a dependence relationship between the two random variables , infant mortality and child nutrition , and in order to detect this we employ a copula approach to model specification. The results suggest, for example, that while male children have a significantly lower likelihood of surviving their first year relative to female children, should they survive they have significantly better height-for-age Z -scores. From a policy perspective, household wealth and public health interventions such as vaccinations are found to be important predictors of better nutritional outcomes. Copyright © 2008 John Wiley & Sons, Ltd. [source] Deaths on the liver transplant waiting list: An analysis of competing risks,HEPATOLOGY, Issue 2 2006W. Ray Kim The usual method of estimating survival probabilities, namely the Kaplan-Meier method, is suboptimal in the analysis of deaths on the transplant waiting list. Death, transplantation, and withdrawal from list must all be considered. In this analysis, we applied the competing risk analysis method, which allows evaluating these end points individually and simultaneously, to compare the risk of waiting list death across era, blood types, liver disease diagnosis, and severity (Model for End-stage Liver Disease; MELD). Of 861 patients registered on the waiting list at Mayo Clinic Rochester between 1990 and 1999, 657 (76%) patients underwent transplantation, 82 (10%) died while waiting, 41 (5%) withdrew from the list, and 81 (9%) patients were still waiting as of February 2002. The risk of death at 3 years was 10% by the competing risk analysis. During the study period, the median time to transplantation increased from 45 to 517 days. In univariate analyses, there was no significant difference in the risk of death by era of listing (P = .25) or blood type (P = .31), whereas the risk of death was significantly higher in patients with alcohol-induced liver disease and those with higher MELD score (P < .01). A multivariable analysis showed that after adjusting for MELD, blood type, and diagnosis, patients listed in the latter era had higher mortality. In conclusion, the competing risk analysis method is useful in estimating the risk of death among patients awaiting liver transplantation. (HEPATOLOGY 2006;43:345,351.) [source] Nest-site selection by Great Bustards Otis tarda suggests a trade-off between concealment and visibilityIBIS, Issue 1 2010MARINA MAGAÑA Great Bustards Otis tarda have expanded their habitat range from historical occupancy of natural steppes to arable farmland, where the species initially benefited from favourable feeding conditions. More recently, the species has suffered severe declines due partly to agricultural intensification. Nest losses and juvenile mortality are amongst the factors most seriously affecting survival probabilities of many populations of this endangered species, suggesting that management of nesting habitats would bring conservation benefits. We studied nest-site selection in a Great Bustard population of central Spain by radiotracking 42 females for periods of between 1 and 4 years. Females selected nest-sites in fallows or cereal fields, in areas of low patch-type diversity, far from human infrastructure, and with good horizontal visibility. These results suggest that females look for shelter, but also need to have good visibility while incubating, and they support the hypothesis that nest selection is a trade-off between concealment and visibility. We interpret both preferences as adaptations to reduce predation pressure, one of the main causes of nest failure in this species. Nests were placed on slopes significantly orientated to the southeast, which suggests that females also seek sites protected from the cold north-westerly winds that are prevalent in the study area. To reduce nest destruction, harvesting should be delayed as long as possible and habitat conservation measures should not be restricted to lek sites but also include nesting areas, which are frequently located far from leks. [source] Resident and transient dynamics, site fidelity and survival in wintering Blackcaps Sylvia atricapilla: evidence from capture,recapture analysesIBIS, Issue 2 2007EDUARDO J. BELDA In their winter quarters, migrant birds may either remain within a small area (resident strategy) or move frequently over a large area looking for locally abundant food (transient strategy). It has been suggested that both strategies could simultaneously occur in the same population. We used time-since-marking capture,recapture models to infer the coexistence of these two behavioural strategies (transient and resident) among wintering Blackcaps Sylvia atricapilla using weekly recapture data over a 7-year period. A related question is whether Blackcaps, if surviving to the next winter, always return to the same wintering area, so we also used this approach to analyse winter site fidelity and to estimate annual survival probabilities. Model selection supported the existence of heterogeneity in survival estimates for both the within-season and the interannual survival probabilities, i.e. there was evidence for the existence of transients. It was estimated that 26% of the Blackcaps were resident during the winter. Mean apparent annual survival probability was 0.46 (se = ±0.11). However, there was some evidence suggesting that not all individuals showed winter site fidelity. The estimated proportion of individuals that, if alive, returned to the wintering area was 28%. This is the first study to show the existence of these two behavioural strategies (residence and transience) among wintering Blackcaps, and the first confirming this pattern using capture,recapture models. These models considering transient and resident dynamics may become an important tool with which to analyse wintering strategies. [source] A closer look at the relationship between life expectancy and economic growthINTERNATIONAL JOURNAL OF ECONOMIC THEORY, Issue 2 2009Théophile T. Azomahou O41; I20; J10 We first provide a nonparametric inference of the relationship between life expectancy and economic growth using historical data for 18 countries over the period 1820,2005. The obtained shape indicates convexity for low enough values of life expectancy and concavity for large enough values. We then study this relationship using a benchmark model combining "perpetual youth" and learning-by-investing. The generated relationship between life expectancy and economic growth is shown to be strictly increasing and concave. We finally examine two models departing from "perpetual youth" by assuming successively age-dependent earnings and age-dependent survival probabilities. With age-dependent earnings, the obtained relationship is hump-shaped, whereas age-dependent survival laws reproduce the convex,concave shape detected in prior empirical study. [source] The role of group size and environmental factors on survival in a cooperatively breeding tropical passerineJOURNAL OF ANIMAL ECOLOGY, Issue 6 2006LYANNE BROUWER Summary 1Variation in survival, a major determinant of fitness, may be caused by individual or environmental characteristics. Furthermore, interactions between individuals may influence survival through the negative feedback effects of density dependence. Compared to species in temperate regions, we have little knowledge about population processes and variation in fitness in tropical bird species. 2To investigate whether variation in survival could be explained by population size or climatic variables we used capture,recapture models in conjunction with a long-term data set from an island population of the territorial, cooperatively breeding Seychelles warbler (Acrocephalus sechellensis). The lack of migration out of the study population means that our results are not confounded by dispersal. 3Annual survival was high, both for adults (84%) and juveniles (61%), and did not differ between the sexes. Although there was significant variation in survival between years, this variation could not be explained by overall population size or weather variables. 4For territorial species, resource competition will work mainly on a local scale. The size of a territory and number of individuals living in it will therefore be a more appropriate measure of density than overall population density. Consequently, both an index of territory quality per individual (food availability) and local density, measured as group size, were included as individual covariates in our analyses. 5Local density had a negative effect on survival; birds living in larger groups had lower survival probabilities than those living in small groups. Food availability did not affect survival. 6Our study shows that, in a territorial species, although density-dependent effects might not be detectable at the population level they can be detected at the individual territory level , the scale at which individuals compete. These results will help to provide a better understanding of the small-scale processes involved in the dynamics of a population in general, but in particular in tropical species living in relatively stable environments. [source] Nest survival for two species of manakins (Pipridae) in lowland EcuadorJOURNAL OF AVIAN BIOLOGY, Issue 3 2008Thomas B. Ryder Estimates of reproductive success are essential to understand life-history strategies, yet tropical species remain under-studied relative to their temperate counterparts. Here, we report nest survival probabilities for two manakin species (Pipridae). We monitored 61 wire-tailed manakin Pipra filicauda and 45 blue-crowned manakin Lepidothrix coronata nests during three breeding seasons. Both species suffered high nest failure (84%). We modeled the effects of year, nest height, nest age (for P. filicauda only), as well as nest manipulation on daily survival rates (DSR) using program MARK. DSR decreased with nest age in P. filicauda whereas a constant survival model was best fitted for L. coronata. Average DSR was 89% for P. filicauda and 85% for L. coronata. This study reports some of the lowest nest survival rates among tropical passerines and poses important questions about population maintenance. [source] Aromatic plants in blue tit Cyanistes caeruleus nests: no negative effect on blood-sucking Protocalliphora blow fly larvaeJOURNAL OF AVIAN BIOLOGY, Issue 2 2008Adèle Mennerat Nesting birds use several behavioural or physiological defence mechanisms against parasites. On Corsica, female blue tits Cyanistes caeruleus incorporate fresh fragments of a limited number of aromatic plants in the nest cup, from the end of nest construction until fledging. Some of these plants negatively affect bacterial growth and host location by blood-sucking mosquitoes in laboratory conditions. In natural populations, Corsican blue tit chicks are exposed to the highest levels of blood-sucking ectoparasitic blow flies Protocalliphora spp. reported in Europe. These ectoparasites can have severe negative effects on chick development and survival probabilities, especially when food constraints are elevated. Here we investigated in several natural Corsican blue tit populations the hypothesis that aromatic plants brought to the nest have anti-blow fly effects during the chick-rearing stage. We predicted that: 1) the amount of aromatic plants should be negatively related to blow fly infestation intensity across nests, 2) experimental addition of aromatic plants in nests should reduce blow fly infestation intensity, and 3) nestlings should be in better physical condition in nests where aromatic plants were experimentally added. No significant relation was found between amount of aromatic plants in nests and blow fly infestation intensity. Experimental addition of aromatic plants did not reduce blow fly infestation intensity and did not affect the chick phenotypic parameters we measured. We conclude that aromatic plants in blue tit nests are not used as a defence against ectoparasitic Protocalliphora blow flies in our study population. [source] Reproductive investment in relation to survival risk in a livebearing fishJOURNAL OF FISH BIOLOGY, Issue 2003K. Lindström Animals are expected to change their allocation of resources into offspring depending on their future survival probabilities. Under environmental conditions where survival probabilities are low, we expect to see an increased investment in current reproduction. Fish show an exceptionally wide range of reproductive modes, including systems where parents can be expected to have extensive control of investment in their offspring. In the least killifish, Heterandria formosa, a small livebearing fish, fertilization is internal and females extensively provision developing embryos. Hence females are likely to have control over parturition time and size of their offspring. Our expectation was that under predator threat females should produce offspring at a higher rate than in control situations. Females were given visual and chemical exposure to mosquito fish and sunfish predators. The time until the birth of the first brood was longer in the presence of predators than in the control. However, subsequent birth intervals showed the opposite pattern. In the presence of predators ensuing brood intervals were shorter than in the control treatment. The effect of mosquito fish and sunfish was similar. Despite the decrease in pregnancy interval, newborn offspring were still larger in the presence of sunfish. Our results suggest that the initial response of refraining from reproduction later changes to an increased reproductive output. This increase, however, did not manifest itself as a quality vs. number trade-off as offspring were also bigger in the sunfish treatment. This suggests that reproductive investment increases in the presence of predators and this may represent terminal investment. [source] Mortality Heterogeneity and the Distributional Consequences of Mandatory AnnuitizationJOURNAL OF RISK AND INSURANCE, Issue 4 2008Guan Gong This article investigates the distributional consequences of mandatory annuitization. Using Health and Retirement Study (HRS) data and accounting for longevity risk pooling within marriage and preannuitized wealth, we find substantial redistribution away from disadvantaged groups in expected utility terms. Using HRS data on subjective survival probabilities, we construct a subjective life table for each individual in the HRS. We calculate the value each household would place on annuitization, based on the husband and wife's subjective life tables, and the household's degree of risk aversion and proportion of preannuitized wealth. A significant minority would perceive themselves as suffering a loss from mandatory annuitization. [source] Factors influencing Soay sheep survivalJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 4 2000E. A. Catchpole We present a survival analysis of Soay sheep mark recapture and recovery data. Unlike previous conditional analyses, it is not necessary to assume equality of recovery and recapture probabilities; instead these are estimated by maximum likelihood. Male and female sheep are treated separately, with the higher numbers and survival probabilities of the females resulting in a more complex model than that used for the males. In both cases, however, age and time aspects need to be included and there is a strong indication of a reduction in survival for sheep aged 7 years or more. Time variation in survival is related to the size of the population and selected weather variables, by using logistic regression. The size of the population significantly affects the survival probabilities of male and female lambs, and of female sheep aged 7 or more years. March rainfall and a measure of the North Atlantic oscillation are found to influence survival significantly for all age groups considered, for both males and females. Either of these weather variables can be used in a model. Several phenotypic and genotypic individual covariates are also fitted. The only covariate which is found to influence survival significantly is the type of horn of first-year female sheep. There is a substantial variation in the recovery probabilities over time, reflecting in part the increased effort when a population crash was expected. The goodness of fit of the model is checked by using graphical procedures. [source] Local asymptotic normality and efficient estimation for INAR(p) modelsJOURNAL OF TIME SERIES ANALYSIS, Issue 5 2008Feike C. Drost Abstract., Integer-valued autoregressive (INAR) processes have been introduced to model non-negative integer-valued phenomena that evolve in time. The distribution of an INAR(p) process is determined by two parameters: a vector of survival probabilities and a probability distribution on the non-negative integers, called an immigration distribution. This paper provides an efficient estimator of the parameters, and in particular, shows that the INAR(p) model has the Local Asymptotic Normality property. [source] Differential Mortality and the Design of the Italian System of Public PensionsLABOUR, Issue 2003Graziella Caselli After reviewing the secular trends in elderly mortality in Italy, and the evolution of regional differences in survival over the last three decades, we evaluate the impact, on the conversion factors introduced by the Dini reform, of a further decline in elderly mortality over the next few decades. We compute the conversion factors using a close approximation to the unknown formula employed in the Dini reform but allowing for gender- and region-specific survival probabilities. Our results leave no doubt about the importance of frequently updating the conversion factors in the light of the rapid increase in elderly survival. The paper also quantifies to what extent gender- and region-specific conversion factors may differ from their currently legislated values, that only vary by age. Finally, we recognize that the actuarial fairness of the system introduced by the recent reform can only be guaranteed on average and that, in the presence of a heterogeneous population of individuals that differ considerably in their mortality prospects, the current system implies a substantial degree of redistribution from high-mortality groups (typically characterized by low income and low wealth) to low-mortality groups (typically characterized by high income and high wealth). [source] POPULATION EXTINCTION IN DETERMINISTICAND STOCHASTIC DISCRETE-TIME EPIDEMIC MODELS WITH PERIODIC COEFFICIENTS WITH APPLICATIONS TO AMPHIBIAN POPULATIONSNATURAL RESOURCE MODELING, Issue 2 2006KEITH E. EMMERT ABSTRACT. Discrete-time deterministic and stochastic epidemic models are formulated for the spread of disease in a structured host population. The models have applications to a fungal pathogen affecting amphibian populations. The host population is structured according to two developmental stages, juveniles and adults. The juvenile stage is a post-metamorphic, nonreproductive stage, whereas the adult stage is reproductive. Each developmental stage is further subdivided according to disease status, either susceptible or infected. There is no recovery from disease. Each year is divided into a fixed number of periods, the first period represents a time of births and the remaining time periods there are no births, only survival within a stage, transition to another stage or transmission of infection. Conditions are derived for population extinction and for local stability of the disease-free equilibrium and the endemic equilibrium. It is shown that high transmission rates can destabilize the disease-free equilibrium and low survival probabilities can lead to population extinction. Numerical simulations illustrate the dynamics of the deterministic and stochastic models. [source] Growth,mortality relationships as indicators of life-history strategies: a comparison of nine tree species in unmanaged European forestsOIKOS, Issue 6 2008Jan Wunder Forest succession depends strongly on the life history strategies of individual trees. An important strategic element is the ability to survive unfavourable environmental conditions that result in strongly reduced tree growth. In this study, we investigated whether the relationship between growth and mortality differs among tree species and site conditions. We analysed 10 329 trees of nine tree species (Picea abies, Taxus baccata, Fagus sylvatica, Tilia cordata, Carpinus betulus, Fraxinus excelsior, Quercus robur, Betula spp. and Alnus glutinosa) from unmanaged forests of Europe: the continental Bia,owie,a forest (Poland) and several oceanically influenced Swiss forest reserves. For each species, we calculated a set of flexible logistic regression models with the explanatory variables growth (as measured by relative basal area increment), tree size and site. We selected the species-specific model with the highest goodness-of-fit and calculated its discriminatory power (area under the receiver operating characteristic curve, AUC) and calibration measures. Most models achieved at least a good discriminatory power (AUC>0.7) and the AUC ranged from 0.62 to 0.87; calibration curves did not indicate any overfitting. Almost all growth,mortality relationships differed among species and sites, i.e. there is no universal growth,mortality relationship. Some species such as F. excelsior showed reduced survival probabilities for both unfavourable and very good growth conditions. We conclude that the growth,mortality relationships presented here can contribute to the life-history classification of trees and that they should also help to improve projections of forest succession models. [source] Impacts of Restored Patch Density and Distance from Natural Forests on Colonization SuccessRESTORATION ECOLOGY, Issue 4 2003Hans Jacquemyn Abstract The reduction and fragmentation of forest habitats is expected to have profound effects on plant species diversity as a consequence of the decreased area and increased isolation of the remnant patches. To stop the ongoing process of forest fragmentation, much attention has been given recently to the restoration of forest habitat. The present study investigates restoration possibilities of recently established patches with respect to their geographical isolation. Because seed dispersal events over 100 m are considered to be of long distance, a threshold value of 100 m between recent and old woodland was chosen to define isolation. Total species richness, individual patch species richness, frequency distributions in species occurrences, and patch occupancy patterns of individual species were significantly different among isolated and nonisolated stands. In the short term no high species richness is to be expected in isolated stands. Establishing new forests adjacent to existing woodland ensures higher survival probabilities of existing populations. In the long term, however, the importance of long-distance seed dispersal should not be underestimated because most species showed occasional long-distance seed dispersal. A clear distinction should be made between populations colonizing adjacent patches and patches isolated from old woodland. The colonization of isolated stands may have important effects on the dynamics and diversity of forest networks, and more attention should be directed toward the genetic traits and viability of founding populations in isolated stands. [source] Discrete-time survival treesTHE CANADIAN JOURNAL OF STATISTICS, Issue 1 2009Imad Bou-hamad MSC 2000: Primary 62N99; secondary 62G08 Abstract Tree-based methods are frequently used in studies with censored survival time. Their structure and ease of interpretability make them useful to identify prognostic factors and to predict conditional survival probabilities given an individual's covariates. The existing methods are tailor-made to deal with a survival time variable that is measured continuously. However, survival variables measured on a discrete scale are often encountered in practice. The authors propose a new tree construction method specifically adapted to such discrete-time survival variables. The splitting procedure can be seen as an extension, to the case of right-censored data, of the entropy criterion for a categorical outcome. The selection of the final tree is made through a pruning algorithm combined with a bootstrap correction. The authors also present a simple way of potentially improving the predictive performance of a single tree through bagging. A simulation study shows that single trees and bagged-trees perform well compared to a parametric model. A real data example investigating the usefulness of personality dimensions in predicting early onset of cigarette smoking is presented. The Canadian Journal of Statistics 37: 17-32; 2009 © 2009 Statistical Society of Canada Arbres de survie à temps discret Les méthodes d'arbres sont fréquemment utilisées lors d'études impliquant des données censurées. La structure d'un arbre ainsi que la facilité avec laquelle il peut être interprété font de lui un outil utile afin d'identifier des facteurs de pronostique et de prédire les probabilités de survie conditionnelles d'un individu étant donné ses covariables. Les méthodes existantes ont été développées pour traiter une variable temporelle continue. En pratique, il arrive fréquemment que la variable mesurant le temps de survie soit mesurée selon une échelle discrète. Les auteurs proposent une nouvelle méthode pour construire un arbre qui est spécialement adaptée aux variables de survie à temps discret. Le critère de division peut être vu comme étant une extension, au cas de censure à droite, du critère d'entropie pour une variable catégorielle. La sélection de l'arbre final est basée sur une méthode d'élagage combinée avec une correction bootstrap. Les auteurs présentent également une méthode simple pour améliorer, potentiellement, la performance d'un seul arbre avec le bagging. Une étude par simulation montre que des arbres seuls et des arbres "baggés" performent bien comparativement à un modèle paramétrique. Les auteurs présentent aussi une illustration de la nouvelle méthode avec des vraies données qui investiguent l'utilité d'utiliser des dimensions de la personnalité afin de prévoir le début de l'utilisation de la cigarette. La revue canadienne de statistique 37: 17-32; 2009 © 2009 Société statistique du Canada [source] Bayesian analysis of mark-recapture data with travel time-dependent survival probabilitiesTHE CANADIAN JOURNAL OF STATISTICS, Issue 1 2008Saman Muthukumarana Abstract The authors extend the classical Cormack-Jolly-Seber mark-recapture model to account for both temporal and spatial movement through a series of markers (e.g., dams). Survival rates are modeled as a function of (possibly) unobserved travel times. Because of the complex nature of the likelihood, they use a Bayesian approach based on the complete data likelihood, and integrate the posterior through Markov chain Monte Carlo methods. They test the model through simulations and apply it also to actual salmon data arising from the Columbia river system. The methodology was developed for use by the Pacific Ocean Shelf Tracking (POST) project. Analyse baye,esienne de donne,es de capture-recapture a, I'aide de probabilites de survie dependant du temps de deplacement Les auteurs généralisent le modèle de capture-recapture classique de Cormack-Jolly-Seber pour tenir compte de déplacements spatiaux-temporels signalés par des marqueurs (tels que des barrages). Les taux de survie sont modélisés en fonction de temps de déplacement parfois inobservables. Vu la complexité de la vraisemblance, ils optent pour une approche bayésienne fondée sur la vraisemblance des données complètes et intègrent la loi a posteriori par des méthodes de Monte-Carlo à cha,ne de Markov. Ils testent le modèle par simulation et l'utilisent pour l'analyse de données sur les saumons du réseau hydrographique de la Columbia. La méthodologie a été développée aux fins du projet POST (Pacific Ocean Shelf Tracking). [source] The Diagnostic Conundrum and Liver Transplantation Outcome for Combined Hepatocellular-CholangiocarcinomaAMERICAN JOURNAL OF TRANSPLANTATION, Issue 5 2010C. Panjala Combined hepatocellular-cholangiocarcinoma (cHCC-CC) is a rare primary liver malignancy with mixed hepatocellular carcinoma (HCC) and cholangiocarcinoma (CC) histological features. It is almost impossible to obtain an accurate, preoperative noninvasive diagnosis of cHCC-CC with tumor markers or cross-sectional abdominal imaging due to the mixed histological features. Despite these difficulties, accurate cHCC-CC diagnosis remains an important goal with prognostic significance. In our study, we retrospectively reviewed the tumor markers: AFP and CA 19-9, and cross-sectional liver imaging, in light of liver explant findings, to identify and characterize cHCC-CC features followed by liver transplantation (LT) outcome analysis. The results from this 12 patient cohort failed to identify characteristic features for cHCC-CC. None of the imaging features helped to identify the cHCC-CC tumor and they mimicked either HCC or CC, depending on the degree of glandular differentiation expressed histologically. In our cHCC-CC LT recipients, the 1-, 3- and 5-year cumulative survival probabilities were 79%, 66% and 16%, respectively with a 5-year survival comparable to or better than LT for intrahepatic CC but poorer than LT for HCC following the Milan criteria. Conceivably explained by its cholangiocarcinoma component the LT outcome for this rare and hard to diagnose tumor appears poor. [source] Development of the New Lung Allocation System in the United StatesAMERICAN JOURNAL OF TRANSPLANTATION, Issue 5p2 2006T. M. Egan This article reviews the development of the new U.S. lung allocation system that took effect in spring 2005. In 1998, the Health Resources and Services Administration of the U.S. Department of Health and Human Services published the Organ Procurement and Transplantation Network (OPTN) Final Rule. Under the rule, which became effective in 2000, the OPTN had to demonstrate that existing allocation policies met certain conditions or change the policies to meet a range of criteria, including broader geographic sharing of organs, reducing the use of waiting time as an allocation criterion and creating equitable organ allocation systems using objective medical criteria and medical urgency to allocate donor organs for transplant. This mandate resulted in reviews of all organ allocation policies, and led to the creation of the Lung Allocation Subcommittee of the OPTN Thoracic Organ Transplantation Committee. This paper reviews the deliberations of the Subcommittee in identifying priorities for a new lung allocation system, the analyses undertaken by the OPTN and the Scientific Registry for Transplant Recipients and the evolution of a new lung allocation system that ranks candidates for lungs based on a Lung Allocation Score, incorporating waiting list and posttransplant survival probabilities. [source] | |||||||||||||||||||||||||||||||||||||||||||