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Mortality Curve (mortality + curve)
Selected AbstractsLower Systolic Blood Pressure Is Associated with Greater Mortality in People Aged 85 and OlderJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 10 2008Lena Molander Bsc OBJECTIVES: To investigate the association between blood pressure and mortality in very old people. DESIGN: Population-based cohort study. SETTING: County of Västerbotten, Sweden. PARTICIPANTS: Half of all subjects aged 85 and all of those aged 90 and 95 and older (N=348) in one urban and five rural municipalities in the north of Sweden. MEASUREMENTS: Among others, supine blood pressure, Mini-Mental State Examination, Barthel Index of activities of daily living, Mini Nutritional Assessment, and body mass index. Information on diagnoses, medications, and 4-year mortality was collected. Associations between blood pressure and mortality were investigated using Cox regression analyses, controlling for a number of diagnoses and health factors. RESULTS: Baseline systolic blood pressure (SBP), diastolic blood pressure, and pulse pressure were all inversely associated with mortality within 4 years according to univariate analysis. SBP was the strongest predictor. In Cox regression analyses, low SBP (,120 mmHg) correlated with greater 4-year all-cause mortality alone and when controlling for health status. This connection persisted after exclusion of deaths within the first year. There was a tendency toward a U-shaped mortality curve for the adjusted model, with SBP of 164.2 mmHg (95% confidence interval=154.1,183.8 mmHg) being associated with the lowest mortality. CONCLUSION: Lower SBP seems to be associated with greater mortality in people aged 85 and older, irrespective of health status. There are indications of a U-shaped correlation between SBP and mortality, and the optimal SBP for this age group could be above 140 mmHg. [source] Biodemographic analysis of male honey bee mortalityAGING CELL, Issue 1 2005Olav Rueppell Summary Biodemographic studies of insects have significantly enhanced our understanding of the biology of aging. Eusocial insects have evolved to form different groups of colony members that are specialized for particular tasks and highly dependent on each other. These different groups (castes and sexes) also differ strongly in their life expectancy but relatively little is known about their mortality dynamics. In this study we present data on the age-specific flight activity and mortality of male honey bees from two different genetic lines that are exclusively dedicated to reproduction. We show that males initiating flight at a young age experience more flight events during their lifetime. No (negative) relation between the age at flight initiation and lifespan exists, as might be predicted on the basis of the antagonistic pleiotropy theory of aging. Furthermore, we fit our data to different aging models and conclude that overall a slight deceleration of the age-dependent mortality increase at advanced ages occurs. However, mortality risk increases according to the Gompertz,Makeham model when only days with flight activity (active days) are taken into account. Our interpretation of the latter is that two mortality components act on honey bee males during flight: increasing, age-dependent deaths (possibly from wear-and-tear), and age-independent deaths (possibly due to predation). The overall mortality curve is caused by the interaction of the distribution of age at foraging initiation and the mortality function during the active (flight) lifespan. [source] Cultural imagery and statistical models of the force of mortality: Addison, Gompertz and PearsonJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 3 2010Elizabeth L. Turner Summary., We describe selected artistic and statistical depictions of the force of mortality (hazard or mortality rate), which is a concept that has long preoccupied actuaries, demographers and statisticians. We provide a more graphic form for the force-of-mortality function that makes the relationship between its constituents more explicit. The ,Bridge of human life' in Addison's allegorical essay of 1711 provides a particularly vivid image, with the forces depicted as external. The model that was used by Gompertz in 1825 appears to treat the forces as internal. In his 1897 essay Pearson mathematically modernized ,the medieval conception of the relation between Death and Chance' by decomposing the full mortality curve into five distributions along the age axis, the results of five ,marksmen' aiming at the human mass crossing this bridge. We describe Addison's imagery, comment briefly on Gompertz's law and the origin of the term ,force of mortality', describe the background for Pearson's essay, as well as his imagery and statistical model, and give the bridge of life a modern form, illustrating it via statistical animation. [source] A MODEL LIFE TABLE FOR BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) FROM THE INDIAN RIVER LAGOON SYSTEM, FLORIDA, U.S.A.MARINE MAMMAL SCIENCE, Issue 4 2003Megan K. Stolen Abstract Data gathered from 220 stranded bottlenose dolphins (Tursiops truncatus) in the Indian River Lagoon system, Florida, were used to derive a life table. Survivorship curves were fit to the data using Siler's competing-risk model and a maximum likelihood approach. Population growth was estimated to be between r= 0.0 and 0.046 based on the observed numbers of stranded dolphins. Variance in survival rates was estimated using an individual-based, age-structured population projection model. We estimate that the overall annual mortality rate for this population was 9.8% per year. Sex-specific differences in survivorship were apparent with females outliving males. The overall mortality curve resembles that of other large mammals, with high calf mortality and an exponentially increasing risk of senescent mortality. The inclusion of live-capture removals of individuals from this population did not significantly affect the estimation of survival parameters for most age classes. [source] Short-Term Mortality in Relation to Age and Comorbidity in Older Adults with Community-Acquired Bacteremia: A Population-Based Cohort StudyJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 9 2008Mette Søgaard DVM OBJECTIVES: To assess 30-day mortality from bacteremia in relation to age and comorbidity and the association between age and mortality with increasing comorbidity. DESIGN: Population-based cohort study. SETTING: North Jutland County, Denmark. PARTICIPANTS: Adults in medical wards with community-acquired bacteremia, 1995 to 2004. MEASUREMENTS: Smoothed mortality curves and computed mortality rate ratios (MRRs) using Cox regression analysis. RESULTS: Two thousand eight hundred fifty-one patients, 851 aged 15 to 64, 1,092 aged 65 to 79, and 909 aged 80 and older were included. Mortality increased linearly with age. Compared with patients younger than 65, adjusted MRRs in patients aged 65 to 79 and 80 and older were 1.5 (95% confidence interval (CI)=1.2,2.0) and 1.8 (95% CI=1.4,2.3), respectively. Mortality also increased with level of comorbidity. Compared with patients with low comorbidity, adjusted MRRs in patients with medium and high comorbidity were 1.5 (95% CI=1.2,1.8) and 1.7 (95% CI=1.4,2.2), respectively. Regardless of the level of comorbidity, MRRs were consistently higher in older than in younger patients. CONCLUSION: Older age and greater comorbidity predicted mortality, and increasing age-related comorbidity did not explain the effect of age. [source] Insecticide resistance spectra and resistance mechanisms in populations of Japanese encephalitis vector mosquitoes, Culex tritaeniorhynchus and Cx. gelidus, in Sri LankaMEDICAL AND VETERINARY ENTOMOLOGY, Issue 4 2000S. H. P. P. Karunaratne Summary Culex tritaeniorhynchus Giles and Cx. gelidus Theobald (Diptera: Culicidae), both vectors of Japanese encephalitis, were collected in 1984 and 1998 from two disease endemic localities in Sri Lanka: Anaradhapura and Kandy. Using wild-caught adult mosquitoes from light traps, log dosage-probit mortality curves for insecticide bioassays were obtained for three insecticides: malathion (organophosphate), propoxur (carbamate) and permethrin (pyrethroid). LD50 values showed that, in 1998, Cx. tritaeniorhynchus was ,100-fold more resistant to malathion and 10-fold more resistant to propoxur than was Cx. gelidus. This difference was attributed to Cx. tritaeniorhynchus breeding mostly in irrigated rice paddy fields, where it would have been exposed to pesticide selection pressure, whereas Cx. gelidus breeds in other types of aquatic habitats less prone to pesticide applications. Resistance in Cx. tritaeniorhynchus increased between 1984 and 1998, whereas Cx. gelidus remained predominantly susceptible. Propoxur inhibition of acetylcholinesterase (AChE) activity (the target site of organophosphates and carbamates) indicated that in 1998, frequencies of insensitive AChE-based resistance were 9% in Cx. gelidus and 2,23% in Cx. tritaeniorhynchus, whereas in 1984 this resistance mechanism was detected only in 2% of the latter species from Anaradhapura. The AChE inhibition coefficient (ki) with propoxur was 1.86 ± 0.24 × 105 m,1 min,1 for Cx. tritaeniorhynchus from Anaradhapura in 1998. Both species were tested for activity levels of detoxifying glutathione S-trans- ferases (GSTs) and malathion-specific as well as general carboxylesterases. High activities of GSTs and carboxylesterases were detected in Cx. tritaeniorhynchus but not Cx. gelidus. Malathion-specific carboxylesterase was absent from both species. Native polyacrylamide gel electrophoresis resolved two elevated general carboxylesterases, CtrEst,1 and CtrEst,1, from Cx. tritaeniorhynchus and none from Cx. gelidus. CtrEst,1 was the most intensely staining band. Gel inhibition experiments showed that both elevated esterases were inhibited by organophosphates and carbamates but not by pyrethroids. The major elevated esterase CtrEst,1 was partially purified (15-fold) by sequential Q-Sepharose and phenyl Sepharose column chromatography. The bimolecular rate constant (ka) and the deacylation rate constant (k3) for the malaoxon/ enzyme interaction were 9.9 ± 1.1 × 103 m,1 min,1 and 3.5 ± 0.05 × 10,4m,1 min,1, respectively, demonstrating that the role of this enzyme in organophosphorus insecticide resistance is sequestration. [source] Quantification of collider-stratification bias and the birthweight paradoxPAEDIATRIC & PERINATAL EPIDEMIOLOGY, Issue 5 2009Brian W. Whitcomb Summary The ,birthweight paradox' describes the phenomenon whereby birthweight-specific mortality curves cross when stratified on other exposures, most notably cigarette smoking. The paradox has been noted widely in the literature and numerous explanations and corrections have been suggested. Recently, causal diagrams have been used to illustrate the possibility for collider-stratification bias in models adjusting for birthweight. When two variables share a common effect, stratification on the variable representing that effect induces a statistical relation between otherwise independent factors. This bias has been proposed to explain the birthweight paradox. Causal diagrams may illustrate sources of bias, but are limited to describing qualitative effects. In this paper, we provide causal diagrams that illustrate the birthweight paradox and use a simulation study to quantify the collider-stratification bias under a range of circumstances. Considered circumstances include exposures with and without direct effects on neonatal mortality, as well as with and without indirect effects acting through birthweight on neonatal mortality. The results of these simulations illustrate that when the birthweight,mortality relation is subject to substantial uncontrolled confounding, the bias on estimates of effect adjusted for birthweight may be sufficient to yield opposite causal conclusions, i.e. a factor that poses increased risk appears protective. Effects on stratum-specific birthweight,mortality curves were considered to illustrate the connection between collider-stratification bias and the crossing of the curves. The simulations demonstrate the conditions necessary to give rise to empirical evidence of the paradox. [source] Z -scores and the birthweight paradoxPAEDIATRIC & PERINATAL EPIDEMIOLOGY, Issue 5 2009Enrique F. Schisterman Summary Investigators have long puzzled over the observation that low-birthweight babies of smokers tend to fare better than low-birthweight babies of non-smokers. Similar observations have been made with regard to factors other than smoking status, including socio-economic status, race and parity. Use of standardised birthweights, or birthweight z -scores, has been proposed as an approach to resolve the crossing of the curves that is the hallmark of the so-called birthweight paradox. In this paper, we utilise directed acyclic graphs, analytical proofs and an extensive simulation study to consider the use of z -scores of birthweight and their effect on statistical analysis. We illustrate the causal questions implied by inclusion of birthweight in statistical models, and illustrate the utility of models that include birthweight or z -scores to address those questions. Both analytically and through a simulation study we show that neither birthweight nor z -score adjustment may be used for effect decomposition. The z -score approach yields an unbiased estimate of the total effect, even when collider-stratification would adversely impact estimates from birthweight-adjusted models; however, the total effect could have been estimated more directly with an unadjusted model. The use of z -scores does not add additional information beyond the use of unadjusted models. Thus, the ability of z -scores to successfully resolve the paradoxical crossing of mortality curves is due to an alteration in the causal parameter being estimated (total effect), rather than adjustment for confounding or effect decomposition or other factors. [source] | |||||||||||||