Birth cohort effects on the quantity and heritability of alcohol consumption in adulthood: A Finnish longitudinal twin study

Aims: To explore the importance of birth cohort for alcohol consumption and abstinence over the life course, and to study differences between birth cohorts in genetic and environmental sources of variation in adult alcohol... [ view full abstract ]

Aims: To explore the importance of birth cohort for alcohol consumption and abstinence over the life course, and to study differences between birth cohorts in genetic and environmental sources of variation in adult alcohol use. Design: The Older Finnish Twin Cohort longitudinal survey study 1975–2011. Setting: Same-sex twins from the general population of Finland. Participants: A total of 26 121 individuals aged 18–95 (full twin pairs at baseline n=11 608). Measurements: Longitudinal survey data on monthly alcohol consumption, collected in 1975, 1981, 1990, and 2011. Findings: Hierarchical growth curve models indicated that mean levels of alcohol consumption were the highest in more recent birth cohorts, and alcohol use declined due to aging in earlier-born cohorts. Abstaining was less common in every successive cohort. Aging was associated with increasing abstinence only in the earliest cohorts. Birth cohort differences in the genetic and environmental components of variance in alcohol consumption were found: heritability was 21% (95% CI: 0–56%) in an earlier-born cohort of women (born 1901–1920; mean age 62.8, SD = 5.3) and 51% (95% CI: 36–56%) in a more recent cohort (born 1945–1957; mean age 60.2, SD = 3.7) at the age of 54–74. For men, heritability was 39% (95% CI: 27–45%) in both cohorts. In alcohol abstinence, environmental influences shared between co-twins explained a large proportion of the variation in the earlier-born cohort (43%, 95% CI: 23–63%), whereas non-shared environmental (54%, 95% CI: 39–72%) and additive genetic influences (40%, 95% CI: 13–61%) were more important among more recent cohorts of men and women. Conclusion: In Finland, the quantity of alcohol consumption as well as its heritability in adulthood have increased in more recent birth cohorts, suggesting genetic influences have been moderated by changes in environmental conditions.