Childhood conditions, migration, and mortality: Migrants and natives in 19th‐century cities

Exploring familial factors in the migrant mortality advantage among domestic migrants in later life: Zeeland, the Netherlands, 1812-1962

Many historical and contemporary studies have shown that migrants enjoy survival advantages over non-migrants, even if they originate from higher mortality regimes and have a lower socio-economic and educational status compared to non-migrants in the destination area. This so-called migrant mortality advantage or healthy migrant effect is explained in various ways. One of the main explanations refers to selection effects in the area of origin in the sense that healthier individuals are more likely to move compared to less healthy individuals. So far life-course analysis on the healthy migrant effect were focused on the survival chances of individual migrants compared to non-migrants. However, kin members of migrants might also enjoy survival advantages, given that health and mortality are often clustered in families due to shared environments, behaviors, resources, and household dynamics. We study whether kin members of migrants within the Dutch province of Zeeland also enjoy survival advantages. Although we find a mortality advantage for the migrating men and women in our sample, we find no mortality advantage for their siblings or offspring. However, there was a gendered effect of familial migration in the sense that women, contrary to men, had higher mortality risks if their siblings and parents migrated.

Families in comparison: An individual-level comparison of life-course and family reconstructions between population and vital event registers

It remains unknown how different types of sources affect the reconstruction of life courses and families in large-scale databases increasingly common in demographic research. Here, we compare family and life-course reconstructions for 495 individuals simultaneously present in two well-known Dutch data sets: LINKS, based on the Zeeland province's full-population vital event registration data (passive registration), and the Historical Sample of the Netherlands (HSN), based on a national sample of birth certificates, with follow-up of individuals in population registers (active registration). We compare indicators of fertility, marriage, mortality, and occupational status, and conclude that reconstructions in the HSN and LINKS reflect each other well: LINKS provides more complete information on siblings and parents, whereas the HSN provides more complete life-course information. We conclude that life-course and family reconstructions based on linked passive registration of individuals constitute a reliable alternative to reconstructions based on active registration, if case selection is carefully considered.

Salmon Bias or Red Herring? : Comparing Adult Mortality Risks (Ages 30-90) between Natives and Internal Migrants: Stayers, Returnees and Movers in Rotterdam, the Netherlands, 1850-1940

The purpose of this research is to empirically test the salmon bias hypothesis, which states that the “healthy migrant” effect—referring to a situation in which migrants enjoy lower mortality risks than natives—is caused by selective return-migration of the weak, sick, and elderly. Using a unique longitudinal micro-level database—the Historical Sample of the Netherlands—we tracked the life courses of internal migrants after they had left the city of Rotterdam, which allowed us to compare mortality risks of stayers, returnees, and movers using survival analysis for the study group as a whole, and also for men and women separately. Although migrants who stayed in the receiving society had significantly higher mortality risks than natives, no significant difference was found for migrants who returned to their municipality of birth (returnees). By contrast, migrants who left for another destination (movers) had much lower mortality risks than natives. Natives who left Rotterdam also had significantly lower mortality risks than natives who stayed in Rotterdam. Female migrants, in particular, who stayed in the receiving urban society paid a long-term health price. In the case of Rotterdam, the salmon bias hypothesis can be rejected because the lower mortality effect among migrants was not caused by selective return-migration. The healthy migrant effect is real and due to a positive selection effect: Healthier people are more likely to migrate.

Phenotype-environment mismatch due to epigenetic inheritance? Programming the offspring's epigenome and the consequences of migration

OBJECTIVE

It has been suggested that epigenetic inheritance is an important factor influencing mortality. We use data about the historical population of Québec (years 1670-1740) to study whether parents modify their offspring's phenotype epigenetically prior to conception in response to predicted/perceived mortality. If so, children growing up in the predicted environment enjoy a phenotype-environment-match that should lower mortality, whereas children growing up in a nonpredicted environment should have a higher mortality.

METHODS

We use the large urban-rural mortality differential to capture the predicted/perceived mortality environment. We categorize children into different groups by their migration status: conceived and living in the same environment (urban or rural); conceived in one but born in another environment (urban-to-rural or rural-to-urban); and born in one but migrating to another environment. We use Kaplan-Meier survival curves and fixed effect survival models to estimate to what extent child survival up to the age of 15 depends on migration status.

RESULTS

Child mortality within families that moved from urban to rural areas does not depend on the child's migration status. Within families that moved to urban areas, children who were conceived and born in the rural areas exhibit the lowest mortality. This contradicts a phenotype-environment-mismatch scenario, which would result in higher rather than lower mortality.

CONCLUSION

We do not find evidence for functional (adaptive) epigenetic inheritance. Migration into an environment with lower or higher extrinsic mortality affects child mortality within the families differently than predicted by the concept of epigenetic inheritance. The results suggest that epigenetic inheritance may not be important for child mortality among migrants.

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

OBJECTIVES

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.

METHODS

I used Cox proportional hazard models of mortality after the age of 60 years among historical cohorts of French Canadian women born before 1750. Models are stratified by siblings to adjust the results for unobserved factors shared by family members.

RESULTS

A birth during winter conferred the best-survival prospects in the south of the Saint-Lawrence River but the worse prospects in the north, where a birth during the fall was associated with the lowest mortality. Women who migrated to live on the other side of the river lost whatever advantage or disadvantage they had from their birth season and faced increases or decreases in risk that were specific to their new location.

CONCLUSIONS

Based on Hales and Barker's thrifty phenotype hypothesis, and adding the "hopeful phenotype" counterpart, this study suggests that cues from the external environment during development are highly specific to that environment and that the slightest change of location may affect the chances for survival into old age. I finally address the role of fertility as a possible mediator or modifier of the effect of birth season on longevity.

Biodemography of exceptional longevity: early-life and mid-life predictors of human longevity

This study explores the effects of early-life and middle-life conditions on exceptional longevity using two matched case-control studies. The first study compares 198 validated centenarians born in the United States between 1890 and 1893 to their shorter-lived siblings. Family histories of centenarians were reconstructed and exceptional longevity validated using early U.S. censuses, the Social Security Administration Death Master File, state death indexes, online genealogies, and other supplementary data resources. Siblings born to young mothers (aged less than 25 years) had significantly higher chances of living to 100 compared to siblings born to older mothers (odds ratio = 2.03, 95% CI = 1.33-3.11, p = .001). Paternal age and birth order were not associated with exceptional longevity. The second study explores whether people living to 100 years and beyond differ in physical characteristics at a young age from their shorter-lived peers. A random representative sample of 240 men who were born in 1887 and survived to age 100 was selected from the U.S. Social Security Administration database and linked to U.S. World War I civil draft registration cards collected in 1917 when these men were 30 years old. These validated centenarians were then compared to randomly selected controls who were matched by calendar year of birth, race, and place of draft registration in 1917. Results showed a negative association between "stout" body build (being in the heaviest 15 percent of the population) and survival to age 100. Having the occupation of "farmer" and a large number of children (4 or more) at age 30 increased the chances of exceptional longevity. The results of both studies demonstrate that matched case-control design is a useful approach in exploring effects of early-life conditions and middle-life characteristics on exceptional longevity.

Mortality in late nineteenth-century Montreal: geographic pathways of contagion

In the City of Montreal, 1881, the presence of three cultural communities with different profiles of economic status makes it possible to observe the way social settings affected survival over a lifetime. Regression models show culturally determined maternal factors dominant for infants, and persistent throughout childhood. For post-neonates, children aged 1-4, and adults aged 15-59 household poverty has a comparable effect. Among adults, a gender penalty differs among the three communities. Models are improved when differentiated by cause of death. Locating households using a GIS reveals high levels of residential segregation by ethnicity and income, spatial correlation of environmental hazards, and constraints on exit from zones of risk, which together produce neighbourhood effects as large as household effects. Attention to groups excluded (foundlings and inmates of institutions) confirms that models limited to full household-level information significantly underestimate the impacts of poverty and exclusion.

Long-term mortality consequences of childhood family context in Liaoning, China, 1749-1909

We examine the effects on adult and old age mortality of childhood living arrangements and other aspects of family context in early life. We focus on features of family context that have already been shown to be associated with infant or child mortality in historical and developing country populations. We apply discrete-time event-history analysis to longitudinal, individual-level household register data for a rural population in northeast China from the eighteenth and nineteenth centuries. Loss of a mother in childhood, a short preceding birth interval, and high maternal age were all associated with elevated mortality risks later in life. Such effects persist in a model with fixed effects that account for unobserved characteristics of the community and household. An important implication of these results is that in high-mortality populations, features of early-life family context that are associated with elevated infant and child mortality may also predict adverse mortality outcomes in adulthood.