Impact of social inequalities at birth on the longevity of children born 1914-1916: A cohort study.

Background: Testing whether familial socioeconomic status (SES) in childhood is a predictor of mortality has rarely been done on historical cohorts.

Methods: The birth certificates of 4,805 individuals born 1914-1916 in 16 districts of the Paris region were retrieved. The handwritten information provided the occupation of parents, the legitimacy status, life events (e.g. marriage, divorce), and the precise date of death when after 1945 (i.e. age 31 years (y) in the cohort). We used the median age at death (MAD) as a global measure of mortality, then studied separately survival to and after 31 y. Multivariate Imputation by Chained Equations (MICE), Generalized Additive Models (GAMs) and mixed effect Cox models were used.

Results: MAD showed large variations according to paternal occupation. The lowest MAD in both sexes was that of workers' children: it was 56.3 y (95% CI: [48.6-62.7]) in men and 67.4 y (95% CI: [60.8-72.7]) in women, respectively (95% CI: 13.4 y [5.7-21.3]) and 12.3 y (95% CI: [4.0-19.2]) below the highest MAD attained. MAD experienced by illegitimate children was 18.9 y (95% CI: [13.3-32.3]) shorter than of legitimate children. The multivariate analysis revealed that in both sexes survival to age 31 y was predicted independently by legitimacy and paternal occupation. Paternal occupation was found significantly associated with mortality after age 31 y in females only: accordingly difference in life expectancy at age 31 y was 4.4 y (95% CI: [1.2-7.6]) between upper class and workers' daughters.

Conclusions: Paternal occupation and legitimacy status were strong predictors of offspring longevity in this one-century historical cohort born during World War One.