The impact of heterogeneity in individual frailty on the dynamics of mortality

Vaupel, James W.; Mantón, Kenneth G.; Stallard, Eric

doi:10.2307/2061224

Cited by 2,156 publications

(1,683 citation statements)

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“…Esse tipo de heterogeneidade pode ser resultado de erros de medida ou da omissão de variáveis explicativas relevantes (Lancaster, 1979;Vaupel, Manton, & Stallard, 1979). De acordo com Heckman e Singer (1984), sempre que a heterogeneidade em dados de duração é testada em estudos microeconômicos o resultado é positivo.…”

Section: Método E Resultadosunclassified

Aumento Do Tempo De Permanência Dos Turistas No Brasil: Novos Turistas Ou Novos Comportamentos?

Santos

Ramos²,

Rey‐Maquieira³

2012

RBTUR

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Resumo: Em todo o mundo a duração média das viagens tem diminuído. No entanto, curiosamente, essa tendência não tem se revelado no turismo receptivo internacional do Brasil. Duas hipóteses podem explicar a incomum realidade brasileira: mudanças no comportamento dos turistas que visitam o país, e alterações na composição do fluxo turístico receptivo internacional brasileiro. Uma eventual confirmação da primeira hipótese mostraria que a evolução do comportamento dos turistas nos últimos anos foi efetivamente diferente no Brasil e nos demais países, evidenciando a ocorrência de melhorias na qualidade da experiência turística ofertada pelo Brasil. Este estudo objetiva testar essa hipótese através do uso de modelos de duração baseados em mais de 211 mil entrevistas. A modelagem do comportamento individual dos turistas torna possível controlar o efeito de variáveis intervenientes, permitindo uma avaliação detalhada do efeito temporal sobre a duração esperada das estadas dos turistas. Treze modelos de duração são testados. O modelo com melhor ajuste aos dados tem taxa de risco com distribuição Weibull e heterogeneidade individual com distribuição Gama. Os resultados apontam que a tendência crescente da permanência média é parcialmente explicada por uma mudança no comportamento dos turistas. Palavras-chave: Permanência; Duração; Estada; Modelos de duração; Turismo no Brasil. Abstract:The average duration of tourism trips has decreased all over the world. However, curiously, this trend has not been observed in the Brazilian inbound tourism. There are two hypotheses for explaining

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Section: Método E Resultadosunclassified

Aumento Do Tempo De Permanência Dos Turistas No Brasil: Novos Turistas Ou Novos Comportamentos?

Santos

Ramos²,

Rey‐Maquieira³

2012

RBTUR

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“…However, in reality, individuals are heterogeneous in their unobserved factors or frailty, including genetic make-ups, which serves as the basis for existing theories that explain mortality deceleration at advanced ages, among which is the demographic heterogeneity theory by Vaupel et al 13 It follows that, when an individual's unobserved frailty designated as z is gamma-distributed with mean 1 and variance s 2 , instead of (2), the relationship between s 1 (x) and s 0 (x) becomes…”

Section: Methodsmentioning

confidence: 99%

“…9,11,12 Although of great interest, estimating genetic effects on late life survival is confronted with the distinct mortality pattern and sparse genetic data available. In the literature, different theories or models have been proposed to explain the late life-mortality pattern, 8 among them the heterogeneity model, 13 which assumes individual heterogeneity in unobserved frailty that follows a gamma distribution. Jacobsen et al 11 applied a Cox regression model with gamma-distributed frailty to the Danish 1905 birth cohort data to estimate the age-dependent effect on extreme age survival for the ApoE gene, the only gene whose role on longevity has been consistently demonstrated.…”

Section: Introductionmentioning

confidence: 99%

Analyzing age-specific genetic effects on human extreme age survival in cohort-based longitudinal studies

et al. 2012

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The analysis of age-specific genetic effects on human survival over extreme ages is confronted with a deceleration pattern in mortality that deviates from traditional survival models and sparse genetic data available. As human late life is a distinct phase of life history, exploring the genetic effects on extreme age survival can be of special interest to evolutionary biology and health science. We introduce a non-parametric survival analysis approach that combines population survival information with individual genotype data in assessing the genetic effects in cohort-based longitudinal studies. Our approach is characterized by nonparametric analysis of late age survival to capture the observed pattern of mortality deceleration and frailty modeling to account for individual heterogeneity in unobserved frailty. The method is applied to ApoE genotype data in the Danish 1905 birth cohort to estimate effect of the e4 allele. Our results revealed an age-specific relative risk of the allele that increases nonlinearly with age and non-proportional patterns in hazard of death for carriers and non-carriers of the allele, suggesting that the e4 mutation preserves its deleterious effect that progressively affect human survival even at extreme ages.

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“…For any individual, defining the hazard of death at age x (the risk of dying after surviving to age x) as mðxÞ ¼ r i zm 0 ðxÞ; where r i is the relative risk for genotype i ði ¼ 0; 1 or 2Þ; z is an unobserved individual frailty that also affects survival, and m 0 ðxÞ is the baseline hazard function for an individual with both frailty and genotype relative risk set to 1. The corresponding individual survival function is sðxÞ ¼ e Àr i z R x 0 m 0 ðsÞds : To describe the relationship of the three genotypespecific survival functions, Yashin et al [1999] introduced a model that assumes that the unobserved frailty follows a gamma-distribution with mean 1 and variance s 2 [Vaupel et al, 1979;Vaupel and Yashin, 1985], so that mean survival for the subpopulation carrying genotype i is…”

Section: Population and Genotype-specific Survivalsmentioning

confidence: 99%

Power of non‐parametric linkage analysis in mapping genes contributing to human longevity in long‐lived sib‐pairs

Tan

Zhao

Iachine

et al. 2004

Genetic Epidemiology

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This report investigates the power issue in applying the non-parametric linkage analysis of affected sib-pairs (ASP) [Kruglyak and Lander, 1995: Am J Hum Genet 57:439-454] to localize genes that contribute to human longevity using longlived sib-pairs. Data were simulated by introducing a recently developed statistical model for measuring marker-longevity associations [Yashin et al., 1999: Am J Hum Genet 65:1178-1193, enabling direct power comparison between linkage and association approaches. The non-parametric linkage (NPL) scores estimated in the region harboring the causal allele are evaluated to assess the statistical power for different genetic (allele frequency and risk) and heterogeneity parameters under various sampling schemes (age-cut and sample size). Based on the genotype-specific survival function, we derived a heritability calculation as an overall measurement for the effect of causal genes with different parameter settings so that the power can be compared for different modes (dominant, recessive) of inheritance. Our results show that the ASP approach is a powerful tool in mapping very strong effect genes, both dominant and recessive. To map a rare dominant genetic variation that reduces hazard of death by half, a large sample (above 600 pairs) with at least one extremely long-lived (over age 99) sib in each pair is needed. Again, with large sample size and high age cut-off, the method is able to localize recessive genes with relatively small effects, but the power is very limited in case of a dominant effect. Although the power issue may depend heavily on the true genetic nature in maintaining survival, our study suggests that results from small-scale sib-pair investigations should be referred with caution, given the complexity of human longevity. & 2004 Wiley-Liss, Inc.

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The impact of heterogeneity in individual frailty on the dynamics of mortality

Cited by 2,156 publications

References 5 publications

Aumento Do Tempo De Permanência Dos Turistas No Brasil: Novos Turistas Ou Novos Comportamentos?

Aumento Do Tempo De Permanência Dos Turistas No Brasil: Novos Turistas Ou Novos Comportamentos?

Analyzing age-specific genetic effects on human extreme age survival in cohort-based longitudinal studies

Power of non‐parametric linkage analysis in mapping genes contributing to human longevity in long‐lived sib‐pairs

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