Alain Gagnon

Is there a trade-off between fertility and longevity? A comparative study of women from three large historical databases accounting for mortality selection.

Frontier populations provide exceptional opportunities to test the hypothesis of a trade‐off between fertility and longevity. In such populations, mechanisms favoring reproduction usually find fertile ground, and if these mechanisms reduce longevity, demographers should observe higher postreproductive mortality among highly fertile women. We test this hypothesis using complete female reproductive histories from three large demographic databases: the Registre de la population du Québec ancien (Université de Montréal), which covers the first centuries of settlement in Quebec; the BALSAC database (Université du Québec à Chicoutimi), including comprehensive records for the Saguenay‐Lac‐St‐Jean (SLSJ) in Quebec in the nineteenth and twentieth centuries; and the Utah Population Database (University of Utah), including all individuals who experienced a vital event on the Mormon Trail and their descendants. Together, the three samples allow for comparisons over time and space, and represent one of the largest set of natural fertility cohorts used to simultaneously assess reproduction and longevity. Using survival analyses, we found a negative influence of parity and a positive influence of age at last child on postreproductive survival in the three populations, as well as a significant interaction between these two variables. The effect sizes of all these parameters were remarkably similar in the three samples. However, we found little evidence that early fertility affects postreproductive survival. The use of Heckmans procedure assessing the impact of mortality selection during reproductive ages did not appreciably alter these results. We conclude our empirical investigation by discussing the advantages of comparative approaches. Am. J. Hum. Biol., 2009.

Does exposure to infectious diseases in infancy affect old-age mortality? Evidence from a pre-industrial population

Many studies have shown that health conditions experienced in childhood play an important role on an individuals adult mortality. Recent research suggests that past reductions in early life exposure to infectious diseases have been a major contributor to the historical decline in old-age mortality. Drawing on French-Canadian data from cohorts born in the 17th and 18th centuries, we test whether a progressive deterioration in early life conditions (as revealed by an increasing infant mortality rate) translates into a decrease in survival prospects in late life. We use traditional demographic measures such as the age-specific probability of death, and a series of proportional hazard models to control for familial and environmental conditions. Results point toward little evidence of any early life effects. The trend of increasing infant mortality does not correlate with a general increase of mortality in older ages within the same cohorts. Period changes affecting survival at older ages (war, epidemics) as well as demographic and biological characteristics shared within families have a much larger role in old-age mortality than early life characteristics shared within the same cohorts.

Familial Aggregation of Survival and Late Female Reproduction

Women giving birth at advanced reproductive ages in natural fertility conditions have been shown to have superior postmenopausal longevity. It is unknown whether improved survival is more likely among relatives of late-fertile women. This study compares survival past age 50 of men with and without a late-fertile sister in two populations: Utahns born in 1800-1869 identified from the Utah Population Database and Québec residents born in 1670-1750 identified from the Programme de recherche en démographie historique. Male survival was greater for those with, rather than without, a sister reproducing after age 45, particularly among men with at least three sisters (Utah rate ratio [RR] = .801, 95% CI = 0.687-0.940; Quebec RR = .786, 95% CI = 0.664-0.931). Survival of wives was unaffected by whether their husbands had a late-fertile sister, suggesting a weak influence of unmeasured socioenvironmental factors. These results support the hypothesis that late female fertility and slow somatic aging may be promoted by the same genetic variants.

Age-specific mortality during the 1918 influenza pandemic: unravelling the mystery of high young adult mortality.

The worldwide spread of a novel influenza A (H1N1) virus in 2009 showed that influenza remains a significant health threat, even for individuals in the prime of life. This paper focuses on the unusually high young adult mortality observed during the Spanish flu pandemic of 1918. Using historical records from Canada and the U.S., we report a peak of mortality at the exact age of 28 during the pandemic and argue that this increased mortality resulted from an early life exposure to influenza during the previous Russian flu pandemic of 1889–90. We posit that in specific instances, development of immunological memory to an influenza virus strain in early life may lead to a dysregulated immune response to antigenically novel strains encountered in later life, thereby increasing the risk of death. Exposure during critical periods of development could also create holes in the T cell repertoire and impair fetal maturation in general, thereby increasing mortality from infectious diseases later in life. Knowledge of the age-pattern of susceptibility to mortality from influenza could improve crisis management during future influenza pandemics.

Are immigrants healthier than native-born Canadians? A systematic review of the healthy immigrant effect in Canada

ABSTRACT Objectives: Immigrants are typically healthier than the native-born population in the receiving country and also tend to be healthier than non-migrants in the countries of origin. This foreign-born health advantage has been referred to as the healthy immigrant effect (HIE). We examined evidence for the HIE in Canada. Design: We employed a systematic search of the literature on immigration and health and identified 78 eligible studies. We used a narrative method to synthesize the HIE across different stages of the life-course and different health outcomes within each stage. We also examined the empirical evidence for positive selection and duration effects – two common explanations of migrants’ health advantage and deterioration, respectively. Results: We find that the HIE appears to be strongest during adulthood but less so during childhood/adolescence and late life. A foreign-born health advantage is also more robust for mortality but less so for morbidity. The HIE is also stronger for more recent immigrants but further research is needed to determine the critical threshold for when migrants’ advantage disappears. Positive selection as an explanation for the HIE remains underdeveloped. Conclusions: There is an absence of a uniform foreign-born health advantage across different life-course stages and health outcomes in Canada. Nonetheless, it remains the case that the HIE characterizes the majority of contemporary migrants since Canada’s foreign-born population consists mostly of core working age adults.

Why Should Men and Women Marry and Have Children? Parenthood, Marital Status and Self-perceived Stress among Canadians

Using the Canadian Community and Health Survey (2000), this study examines self-perceived stress across marital and parental statuses, adjusting for age, education, work status, income and sense of community belonging. Results show that fatherhood increases perceived stress regardless of marital status, particularly among singles. Motherhood does not affect perceived stress among married or cohabitating women but single and post-married mothers endure the highest levels of stress. Interactions between working and parental or marital statuses are also observed. Community belonging acts as a coping mechanism in lowering stress levels. Results are discussed in the context of changing familial roles.

The relationship between incarceration and premature adult mortality: gender specific evidence.

We examine the relationship between incarceration and premature mortality for men and women. Analyses using the National Longitudinal Survey of Youth (NLSY79) reveal strong gender differences. Using two different analytic procedures the results show that women with a history of incarceration are more likely to die than women without such a history, even after controlling for health status and criminal behavior prior to incarceration, the availability of health insurance, and other socio-demographic factors. In contrast, there is no relationship between incarceration and mortality for men after accounting for these factors. The results point to the importance of examining gender differences in the collateral consequences of incarceration. The results also contribute to a rapidly emerging literature linking incarceration to various health hazards. Although men constitute the bulk of inmates, future research should not neglect the special circumstances of female former inmates and their rapidly growing numbers.

Early life socioeconomic conditions in rural areas and old-age mortality in twentieth-century Quebec

This study examines the effects of early life socioeconomic and residential conditions on adult mortality. The family and residential details of children living in rural areas of Quebec, Canada, in 1901 were linked to their subsequent ages at death using a database compiling information from the 1901 Canadian Census and Quebec vital statistics registers. Survival analysis results suggest that males raised on a farm and in a household owned by their father had lower mortality after the age of fifty than other males from rural areas. Chances for survival at older ages were not equal, however, among males whose father was a farmer. Most notably, males raised on a larger farmstead, an indicator of a higher socioeconomic status, experienced lower risk of mortality than those raised by farmers owning fewer acres. Results were widely different for females, who did not gain an advantage from being raised on a farm, wealthy or not, regardless of homeownership, but instead from having a literate father. Accounting for selection bias and shared frailty among brothers served to enhance the significance and effect size of acreage wealth and of other early life factors in the prediction of male adult mortality risk. This study provides evidence that early life effects on later life health and mortality could often be underestimated, due to a failure to account for selection and unobserved heterogeneity.

Effect of birth season on longevity: thrifty and hopeful phenotypes in historical Quebec.

Individuals with fetal growth restrictions may become unhealthy as adult if they live in a nutritionally rich environment. Yet, there is little evidence for the counterpart that profuse resources during early development may prove detrimental in an impoverished adult environment. Using birth season as a proxy for nutrition in utero, this study tests whether early life effects on longevity are conditional on the environment in which people reside during adulthood.

Is Antigenic Sin Always "Original?" Re- examining the Evidence Regarding Circulation of a Human H1 Influenza Virus Immediately Prior to the 1918 Spanish Flu

What makes the 1918 Spanish influenza pandemic stand out from all the others is its well-known W-shaped mortality signature, which was caused by unusually high mortality among adults aged 20 to 40 [1]. Much debate remains as to the exact reason for this atypical pattern [2]. A contribution by Worobey et al. [3] published recently in the Proceedings of the National Academy of Sciences (PNAS) is no doubt adding important information to this debate. In agreement with previous work [4–7], Worobey et al. propose that the very high mortality experienced by young adults during the 1918 H1N1 virus pandemic was primarily due to their childhood exposure to the heterosubtypic H3-like virus that is thought to have caused the earlier 1889–1890 Russian flu pandemic [3]. As is generally accepted, the authors also presume that older adults had immunological cross-protection from earlier exposures to a putative H1-like virus, which circulated prior the 1890 pandemic. As for the lower mortality of children and adolescents, however, a new and compelling hypothesis is put forward: this pattern may be attributed to the appearance of a new H1 influenza variant in the early 1900s, which would have provided protection in 1918 for individuals born at the turn of the century, presumably exposed early in life (or “primed”) to this new variant. They propose that this H1N8 virus arose from reassortment between an H1 lineage virus and an avian influenza virus sometime between 1901 and 1907, replacing the H3N8 virus of the 1889–1890 pandemic. This phylogenetic reconstitution appears to be supported by (often forgotten) seroarcheological and mortality evidence.