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Recurrent Events (recurrent + event)

Distribution by Scientific Domains

Medical Sciences	57%
Mathematics and Statistics	33%
Life Sciences	9%

Distribution within Medical Sciences

Neurology	24%
General & Internal Medicine	15%

Selected Abstracts

Flexible Estimation of Differences in Treatment-Specific Recurrent Event Means in the Presence of a Terminating Event

BIOMETRICS, Issue 3 2009
Qing Pan
Summary In this article, we consider the setting where the event of interest can occur repeatedly for the same subject (i.e., a recurrent event; e.g., hospitalization) and may be stopped permanently by a terminating event (e.g., death). Among the different ways to model recurrent/terminal event data, the marginal mean (i.e., averaging over the survival distribution) is of primary interest from a public health or health economics perspective. Often, the difference between treatment-specific recurrent event means will not be constant over time, particularly when treatment-specific differences in survival exist. In such cases, it makes more sense to quantify treatment effect based on the cumulative difference in the recurrent event means, as opposed to the instantaneous difference in the rates. We propose a method that compares treatments by separately estimating the survival probabilities and recurrent event rates given survival, then integrating to get the mean number of events. The proposed method combines an additive model for the conditional recurrent event rate and a proportional hazards model for the terminating event hazard. The treatment effects on survival and on recurrent event rate among survivors are estimated in constructing our measure and explain the mechanism generating the difference under study. The example that motivates this research is the repeated occurrence of hospitalization among kidney transplant recipients, where the effect of expanded criteria donor (ECD) compared to non-ECD kidney transplantation on the mean number of hospitalizations is of interest. [source]

The Statistical Analysis of Recurrent Events by Richard J. Cook, Jerald F. Lawless

INTERNATIONAL STATISTICAL REVIEW, Issue 1 2008
David J. Hand
No abstract is available for this article. [source]

Homozygous thermolabile variant of the methylenetetrahy-drofolate reductase gene: a potential risk factor for hyperhomo-cysteinaemia, CVD, and stroke in childhood

DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 4 2001
Mara Prengler
In this study of 118 children (median age 5.1 years; range 6 months to 17 years) with ischaemic stroke or transient ischaemic attack (TIA), 22 children (19%) were homozygous for the thermolabile variant of the methylenetetrahydrofolate reductase allele (t-MTHFR), compared with nine of 78 (12%) of a reference population (p=0.18, OR 1.76, 95% CI 0.76 to 4.04). Of those with cerebrovascular disease (CVD), 17 of 84 were homozygous for the t-MTHFR allele (p=0.13 compared with the reference population (OR 1.95, 95% CI 0.81 to 4.65). There was a significant (p<0.025) increment of plasma total homocysteine concentration in homozygotes for the t-MTHFR allele compared with heterozygotes, negatives for the t-MTHFR allele, and control children with no history of stroke. In four of 12 homozygotes for the t-MTHFR allele, plasma homocysteine levels were raised, compared with three of 38 of those who were negative or heterozygous (p=0.047; OR 5.8, 95% CI 1.1 to 31.2). Homozygotes for the t-MTHFR allele were significantly more likely to have a recurrent event than those who were negative or heterozygous (Cox regression p=0.031, hazard ratio 2.18, 95% CI 1.08 to 4.42). These data suggest that homozygosity for the t-MTHFR allele is associated with raised homocysteine levels in children and is a risk factor for primary and secondary stroke and TIA. [source]

EVOLUTION OF POECILOGONY AND THE BIOGEOGRAPHY OF NORTH AMERICAN POPULATIONS OF THE POLYCHAETE STREBLOSPIO

EVOLUTION, Issue 4 2000
Stefan R. Schulze
Abstract. Invertebrate interspecific developmental patterns can be highly variable and, taxonomically, are considered only weakly constrained. Intraspecifically, some invertebrate species possess multiple developmental modes,a condition known as poecilogony. Closer examination of most putative poecilogenous species, however, has not supported poecilogony, but rather has uncovered hidden or cryptic species. The polychaete Streblospio benedicti is a well-known, poecilogenous species found along the coast of North America. We collected mitochondrial cytochrome subunit I DNA sequence data from 88 individuals taken from 11 locations along the Atlantic, Gulf, and Pacific Coasts of the United States to provide a phylogenetic framework from which to interpret intraspecific variation in larval life history and brooding structure morphology in this species. Our results are consistent with a recent revision of the species into two separate species: S. benedicti, a pouched brooding form distributed along the Atlantic and Pacific Coasts, and S. gynobranchiata, a branchiate brooding form in the Gulf of Mexico. Contrary to the redescription, S. benedicti is paraphyletic because the pouched brooding population in Vero Beach, Florida shows strong genetic affinity with Gulf of Mexico populations (S. gynobranchiata). However, S. benedicti is a true poecilogenous species, with both lecithotrophic and planktotrophic individuals possessing identical mitochondrial DNA haplotypes. Crossbreeding experiments further support the molecular phylogeny with reproductive isolation demonstrated between, but not within, the major phylogenetic clades consistent with the previously described species. The genetic break near Vero Beach, Florida, corresponds to a well-known phylogeographic boundary, but the estimated time of separation for the Streblospio spp., approximately 10 million years before present, predates all other known phylogeographic subdivisions in this area. This suggests that biogeographic sundering in this region is a recurrent event. Divergence times within the major Streblospio spp. clades are recent and indicate that changes in larval life history as well as brooding structure morphology are highly plastic and can evolve rapidly. [source]

Patterns of stroke recurrence according to subtype of first stroke event: the North East Melbourne Stroke Incidence Study (NEMESIS)

INTERNATIONAL JOURNAL OF STROKE, Issue 3 2008
Mahmoud Reza Azarpazhooh
Background Specific information about the nature of recurrent events that occur after each subtype of index stroke may be useful for refining preventive therapies. We aimed to determine whether stroke recurrence rates, the pattern of subtype recurrence, and prescription of secondary prevention agents differed according to initial stroke subtype. Methods Multiple overlapping sources were used to recruit all first-ever stroke patients from a geographically defined region of Melbourne, Australia over a 3-year period from 1996 to 1999. Potential stroke recurrences (fatal and nonfatal) occurring within 2 years of the initial event were identified following patient interview and follow up of death records. Subjects were classified into the different Oxfordshire groups and the type of first-ever stroke was compared with recurrent stroke events. Results One thousand, three hundred and sixteen first-ever strokes were registered during the 3-year period (mean age 74.4 years). A total of 103 first recurrent stroke events (fatal and nonfatal) occurred among those with a first-ever ischemic stroke or intracerebral hemorrhage (ICH) during the 2-year follow-up period. The recurrent stroke subtype was different to the index stroke subtype in most (78%) patients. People with partial anterior circulation infarct had the greatest proportion of recurrences (13%), with a third of these being the more severe total anterior circulation infarct subgroup. The relative risk of ICH after an index lacunar infarct (LACI) compared with an index non-LACI was 4.06 (95% CI 1.10,14.97, P=0.038). Prescription of secondary prevention agents was greater at 2 years after stroke than at hospital discharge, and was similar between ischemic stroke subtypes. Conclusion Approximately 9% of people with first-ever stroke suffered a recurrent event, despite many being prescribed secondary prevention agents. This has implications for the uptake of current preventive strategies and the development of new strategies. The possibility that ICH is greater among index LACI cases needs to be confirmed. [source]

Venous thromboembolism: disease burden, outcomes and risk factors

JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 8 2005
J. A. HEIT
Summary., The epidemiology of venous thromboembolism (VTE) in the community has important implications for VTE prevention and management. This review describes the disease burden (incidence), outcomes (survival, recurrence and complications) and risk factors for deep vein thrombosis and pulmonary embolism occurring in the community. Recent comprehensive studies of the epidemiology of VTE that reported the racial demography and included the full spectrum of disease occurring within a well-defined geographic area over time, separated by event type, incident vs. recurrent event and level of diagnostic certainty, were reviewed. Studies of VTE outcomes had to include a relevant duration of follow-up. VTE incidence among whites of European origin exceeded 1 per 1000; the incidence among persons of African and Asian origin may be higher and lower, respectively. VTE incidence over recent time remains unchanged. Survival after VTE is worse than expected, especially for pulmonary embolism. Thirty percent of patients develop VTE recurrence and venous stasis syndrome. Exposures can identify populations at risk but have a low predictive value for the individual. An acquired or familial thrombophilia may predict the subset of exposed persons who actually develop symptomatic VTE. In conclusion, VTE is a common, lethal disease that recurs frequently and causes serious long-term complications. To improve survival and prevent complications, VTE occurrence must be reduced. Better individual risk stratification is needed in order to modify exposures and target primary and secondary prophylaxis to the person who would benefit most. [source]

Some alternatives in the statistical analysis of sickness absence

AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 10 2009
Albert Navarro
Abstract Purpose Sickness absence (SA) is a commonly used outcome in occupational health cohort studies. Without the use of statistical techniques that take into account that SA is a recurrent event, the probability of obtaining biased estimates of the effects related to SA is very high. The objective of this article is to examine the application of marginal models, comparing them to count-based models, when the outcome of interest is SA. Methods By re-sampling the data of a reference study, 1,000 samples of 1,200 individuals were generated. In each of these samples, the coefficients of two factors were estimated by fitting various models: Poisson, Negative Binomial, standard Cox model for a first occurrence, Andersen,Gill and Prentice,Williams,Peterson. Results In general, differences among the models are observed in the estimates of variances and coefficients, as well as in their distribution. Specifically, the Poisson model estimates the greatest effect for both coefficients (IRR,=,1.17 and IRR,=,1.60), and the Prentice,Williams,Peterson the least effect (HR,=,1.01 and HR,=,1.26). Conclusions Whenever possible, the instantaneous form of analysis should be used for occurrences of a recurrent event. Collection of study data should be organized in order to permit recording of the most complete information possible, particularly regarding event occurrences. This should allow the presence of within-individual heterogeneity and/or occurrence dependency to be studied, and would further permit the most appropriate model to be chosen. When there is occurrence dependence, the choice of a model using the specific baseline hazard seems to be appropriate. Am. J. Ind. Med. 52:811,816, 2009. © 2009 Wiley-Liss, Inc. [source]

ANTERIOR TONGUE CANCER: AGE IS NOT A PREDICTOR OF OUTCOME AND SHOULD NOT ALTER TREATMENT

ANZ JOURNAL OF SURGERY, Issue 11 2003
Michael J. Veness
Background: Mucosal head and neck cancers usually occur in older males after years of smoking and alcohol abuse. Despite this, approximately 5% of cases occur in young adults. The aetiology remains unclear and the anterior tongue is a prevalent site. Prognosis has been reported as worse in young patients and some have proposed a more aggressive treatment approach. Methods: Patients diagnosed with previously untreated anterior tongue squamous cell carcinoma and treated with curative intent were identified. Retrospective and prospective data were collected. Univariate and multivariate analyses were undertaken using Cox regression analysis. The outcome of patients treated with anterior tongue cancer using a cut-off age of 40 years was compared. Results: Between 1980 and 2000, 106 males and 58 females with anterior tongue squamous cell carcinoma were treated at Westmead Hospital. Median follow up was 47 months (6,210 months). Twenty-two patients (13.4%) were aged ,40 years. Other than age, patient demographics, TNM stage and treatment approach were similar between the two groups. Eighty-one per cent had either a T1 or T2 primary. In total, 139 patients (84.8%) had surgery or surgery and radiotherapy. A total of 56 (34%) patients experienced a recurrent event, with nodal recurrence occurring most often as the first site (n = 33, 59%). Young patients had a higher recurrence rate (45.5% vs 32.4%; P = 0.23). Relapse-free survival at 5 years was 62% versus 81% (P = 0.27). Overall survival at 5 years was 65% versus 67% (P = 0.74). Conclusions: In keeping with recently published evidence, young age at diagnosis with anterior tongue cancer did not portend worse outcome. There is therefore currently no strong evidence to support a different treatment approach in young patients. [source]

Flexible Estimation of Differences in Treatment-Specific Recurrent Event Means in the Presence of a Terminating Event

Spontaneous recurrent network activity in organotypic rat hippocampal slices

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2005
Majid H. Mohajerani
Abstract Organotypic hippocampal slices were prepared from postnatal day 4 rats and maintained in culture for >6 weeks. Cultured slices exhibited from 12 days in vitro spontaneous events which closely resembled giant depolarizing potentials (GDPs) recorded in neonatal hippocampal slices. GDP-like events occurred over the entire hippocampus with a delay of 30,60 ms between two adjacent regions as demonstrated by pair recordings from CA3,CA3, CA3,CA1 and interneurone,CA3 pyramidal cells. As in acute slices, spontaneous recurrent events were generated by the interplay of GABA and glutamate acting on AMPA receptors as they were reversibly blocked by bicuculline and 6,7-dinitroquinoxaline-2,3-dione but not by dl -2-amino-5-phosphonopentaoic acid. The equilibrium potentials for GABA measured in whole cell and gramicidin-perforated patch from interconnected interneurones,CA3 pyramidal cells were ,70 and ,56 mV, respectively. The resting membrane potential estimated from the reversal of N -methyl- d -aspartate-induced single-channel currents in cell-attach experiments was ,75 mV. In spite of its depolarizing action, in the majority of cases GABA was still inhibitory as it blocked the firing of principal cells. The increased level of glutamatergic connectivity certainly contributed to network synchronization and to the development of interictal discharges after prolonged exposure to bicuculline. In spite of its inhibitory action, in a minority of cells GABA was still depolarizing and excitatory as it was able to bring principal cells to fire, suggesting that a certain degree of immaturity is still present in cultured slices. This was in line with the transient bicuculline-induced block of GDPs and with the isoguvacine-induced increase of GDP frequency. [source]

The genetics of aspirin resistance

INTERNATIONAL JOURNAL OF CLINICAL PRACTICE, Issue 5 2007
Timothy Goodman
Summary Aspirin is widely used for the prophylaxis of cardiovascular events in patients with cardiovascular risk factors or established atherosclerotic disease. However, despite aspirin treatment, a substantial number of patients experience recurrent events. Such ,aspirin resistance' is generally defined as failure of aspirin to produce an expected biological response, for example inhibition of platelet aggregation or of thromboxane A2 synthesis. Whilst its aetiology is multifactorial, genetic factors are also likely to play their part. Here we review the evidence for and against such a genetic contribution, as well as the data suggesting the involvement of specific genes. [source]

Patterns of stroke recurrence according to subtype of first stroke event: the North East Melbourne Stroke Incidence Study (NEMESIS)

Severe drug-induced skin reactions: clinical pattern, diagnostics and therapy

JOURNAL DER DEUTSCHEN DERMATOLOGISCHEN GESELLSCHAFT, Issue 2 2009
Maja Mockenhaupt
Summary The spectrum of severe drug-induced skin reactions includes not only Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) but also generalized bullous fixed drug eruption (GBFDE), acute generalized exanthematous pustulosis (AGEP) and hypersensitivity syndrome (HSS), also called drug reaction with eosinophilia and systemic symptoms (DRESS). These reactions differ in clinical presentation as well as prognosis, causative agents and therapy. Therefore, the appropriate diagnostic measures should be undertaken rapidly, in order to prove the diagnosis. In addition to a thorough clinical examination, a skin biopsy should be taken and specific laboratory investigations should be done if AGEP or HSS/DRESS is suspected. Since these reactions are drug-induced, the causative agent should be rapidly identified and withdrawn. Besides adequate supportive therapy, systemic immunomodulatory treatments may be considered. Despite intensive care management, the prognosis in SJS and TEN is often poor and influenced by the amount of skin detachment as well as the age of the patients and the pre-existing underlying conditions. Severe sequelae may develop in survivors and affect especially mucosal sites. The prognosis of GBFDE is better but recurrent events may lead to more severe involvement. In HSS/DRESS sequelae have been also described as well as long lasting and recurrent courses, whereas AGEP usually heals without problems. [source]

Introduction: Role of the hospitalist in secondary stroke prevention care,

JOURNAL OF HOSPITAL MEDICINE, Issue S4 2008
David J. Likosky MD
Abstract Stroke is a prevalent and often devastating condition that is likely to affect a growing proportion of the United States population in the coming decades. Individuals who have experienced a stroke or transient ischemic attack are at elevated risk for recurrent events, which are frequently more severe. Therefore, secondary prevention has become the focus of much clinical research and widespread initiatives to deliver evidence-based care. Hospitalists are in a unique position to contribute substantially to these efforts. The 4 articles in this supplement are a call to action for hospital-based physicians. They are based on the conclusions of a panel of hospitalists, neurohospitalists, vascular neurologists, and neurointensivists who met for a roundtable discussion in March 2007. This, the first of the 4 articles, discusses the opportunity for hospitalists to take a leadership role in creating stroke systems of care that integrate secondary stroke prevention with inpatient treatment of acute stroke. The articles that follow will summarize the consensus of roundtable participants on stroke care best practices and their implementation. Journal of Hospital Medicine 2008;3(4 Suppl):S1,S5. © 2008 Society of Hospital Medicine. [source]

Multilevel models for longitudinal data

JOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 1 2008
Fiona Steele
Summary., Repeated measures and repeated events data have a hierarchical structure which can be analysed by using multilevel models. A growth curve model is an example of a multilevel random-coefficients model, whereas a discrete time event history model for recurrent events can be fitted as a multilevel logistic regression model. The paper describes extensions to the basic growth curve model to handle auto-correlated residuals, multiple-indicator latent variables and correlated growth processes, and event history models for correlated event processes. The multilevel approach to the analysis of repeated measures data is contrasted with structural equation modelling. The methods are illustrated in analyses of children's growth, changes in social and political attitudes, and the interrelationship between partnership transitions and childbearing. [source]

Semiparametric Analysis for Recurrent Event Data with Time-Dependent Covariates and Informative Censoring

BIOMETRICS, Issue 1 2010
C.-Y. Huang
Summary Recurrent event data analyses are usually conducted under the assumption that the censoring time is independent of the recurrent event process. In many applications the censoring time can be informative about the underlying recurrent event process, especially in situations where a correlated failure event could potentially terminate the observation of recurrent events. In this article, we consider a semiparametric model of recurrent event data that allows correlations between censoring times and recurrent event process via frailty. This flexible framework incorporates both time-dependent and time-independent covariates in the formulation, while leaving the distributions of frailty and censoring times unspecified. We propose a novel semiparametric inference procedure that depends on neither the frailty nor the censoring time distribution. Large sample properties of the regression parameter estimates and the estimated baseline cumulative intensity functions are studied. Numerical studies demonstrate that the proposed methodology performs well for realistic sample sizes. An analysis of hospitalization data for patients in an AIDS cohort study is presented to illustrate the proposed method. [source]

Semiparametric Transformation Models with Random Effects for Joint Analysis of Recurrent and Terminal Events

BIOMETRICS, Issue 3 2009
Donglin Zeng
Summary We propose a broad class of semiparametric transformation models with random effects for the joint analysis of recurrent events and a terminal event. The transformation models include proportional hazards/intensity and proportional odds models. We estimate the model parameters by the nonparametric maximum likelihood approach. The estimators are shown to be consistent, asymptotically normal, and asymptotically efficient. Simple and stable numerical algorithms are provided to calculate the parameter estimators and to estimate their variances. Extensive simulation studies demonstrate that the proposed inference procedures perform well in realistic settings. Applications to two HIV/AIDS studies are presented. [source]

Marginal Mark Regression Analysis of Recurrent Marked Point Process Data

BIOMETRICS, Issue 2 2009
Benjamin French
Summary Longitudinal studies typically collect information on the timing of key clinical events and on specific characteristics that describe those events. Random variables that measure qualitative or quantitative aspects associated with the occurrence of an event are known as marks. Recurrent marked point process data consist of possibly recurrent events, with the mark (and possibly exposure) measured if and only if an event occurs. Analysis choices depend on which aspect of the data is of primary scientific interest. First, factors that influence the occurrence or timing of the event may be characterized using recurrent event analysis methods. Second, if there is more than one event per subject, then the association between exposure and the mark may be quantified using repeated measures regression methods. We detail assumptions required of any time-dependent exposure process and the event time process to ensure that linear or generalized linear mixed models and generalized estimating equations provide valid estimates. We provide theoretical and empirical evidence that if these conditions are not satisfied, then an independence estimating equation should be used for consistent estimation of association. We conclude with the recommendation that analysts carefully explore both the exposure and event time processes prior to implementing a repeated measures analysis of recurrent marked point process data. [source]

A survival analysis for recurrent events in psychiatric research

BIPOLAR DISORDERS, Issue 2 2004
Christopher Baethge
Objectives:, Time to first recurrence, as analyzed by the Kaplan,Meier (KM) survival analysis, is a commonly applied statistical method in psychiatric research. However, many psychiatric disorders are characterized not by a single event, but rather by recurrent events, such as multiple affective episodes. This study aims to demonstrate a method of survival analysis that takes multiple recurrences into account. Methods:, We examined data on sex differences in a sample of 181 patients undergoing prophylactic treatment with lithium or carbamazepine (serum level assayed) for bipolar disorder (ICD-10). The classical KM method was compared with an approach developed by Peña, Strawderman and Hollander (PSH) that uses recurrent event data to estimate survival function. Results:, The results obtained with the multiple events method differed considerably from those acquired using the standard KM analysis. When taking recurrent event data into account, the probability of remaining well was lower and survival times were longer. In addition, whereas the standard KM analysis indicated that male patients had a higher likelihood of remaining well, the alternative method revealed that both sexes were similarly likely to remain well. Conclusions:, Survival analysis techniques that take recurrent events into account are potentially important instruments for the study of psychiatric conditions characterized by multiple recurrences. In many cases, the standard KM analysis appears to provide only a rough approximation of the course of illness. [source]

Antiplatelet drug response variability and the role of platelet function testing: A practical guide for interventional cardiologists,

CATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS, Issue 1 2009
Dominick J. Angiolillo MD
Abstract Antiplatelet therapy is the cornerstone of treatment for patients with acute coronary syndrome and is also of particular importance in those who undergo percutaneous coronary intervention with stent implantation. Dual antiplatelet therapy with aspirin and clopidogrel is associated with improvement in long-term clinical outcomes in such patients and is presently the antiplatelet therapy of choice for secondary prevention of thrombotic events. However, a significant number of patients experience recurrent events despite antiplatelet therapy. Although poor patient compliance can account for some of these events, particularly in those patients who receive a drug-eluting stent, increasing evidence indicates that there is variability in response to antiplatelet therapy and patients who have higher levels of platelet reactivity are at increased risk for recurrent ischemic events. However, the lack of a consistent definition of inadequate platelet response, as well as the lack of a standardized measurement technique, has made it difficult to define how to treat these patients. To translate findings associated with variability in platelet response into improved patient care, it is necessary to gain a better understanding of what variable platelet response is, how it is measured, who it should be measured in, and what its clinical relevance is. The objective of this review is to evaluate the data regarding interindividual response variability to antiplatelet therapy with the aim of providing practical considerations and where possible, recommendations, regarding this topic for interventional cardiologists. © 2008 Wiley-Liss, Inc. [source]