Birth order and alcohol-related mortality by ethnic origin and national context: Within-family comparisons for Finland and Sweden

Background: Previous studies have found that birth order is an important predictor of later life health, including hospitalisation for alcohol use. We examine the relationship between birth order and alcohol-related mortality in two national contexts, within native families who differ on ethnic origin.

Methods: We study the association between birth order and alcohol-related mortality after age 17, using Finnish register data for cohorts born 1953-1999 and Swedish register data for cohorts born 1940-1999. We apply Cox proportional hazard models and use sibling fixed effects that eliminate confounding by factors shared by siblings. We separate full-sibling groups by ethnic origin, which for Finland means mother’s and father’s Finnish or Swedish ethnolinguistic affiliation. For Sweden, we distinguish native-born according to whether one or both parents were born in Sweden or Finland.

Results: We find a positive correlation between birth order and alcohol-related mortality, but only for ethnic Finns in Finland and primarily men. Within these sibling groups, second-borns have an alcohol-related mortality risk that is 9% higher than that of first-borns, third-borns 19% higher, fourth-borns 23% higher, and fifth- or higher-borns 48% higher. No such birth order associations can be found for any of the other ethnic groups analysed in Finland or Sweden.

Conclusions. Our findings suggest that cultural-related behaviours typical for ethnic groups, and the national context in which they are studied, are relevant for whether any association between birth order and alcohol-related mortality can be observed. Differences in the social interplay within the family may be an important factor.