Effect of birth year on birth weight and obesity in adulthood: comparison between subjects born prior to and during the great depression in Iceland.

Background: Many epidemiological studies have linked small size at birth to adverse adult health outcomes but the relative influence of environmental exposures is less well established.

Methods: The authors investigated the impact of prenatal environmental exposure by comparing 2750 participants born before (1925-1929) and during (1930-1934) the Great Depression in Reykjavik, Iceland. Calendar year served as proxy for environmental effects. Anthropometric measurements at birth and school-age (8-13 years) were collected from national registries. Participants were medically examined as adults (33-65 years).

Results: Mean birth weight, adjusted for maternal age and parity, decreased by 97 g (95% confidence interval (CI): 39, 156) for men and 70 g (95% CI: 11, 129) for women from 1925 to 1934; growth at school-age was significantly reduced for participants growing during the Depression. As adults, women prenatally exposed to the Depression had higher body mass index (Δ0.6 kg/m(2), 95% CI: 0.2, 1.1), higher fasting blood glucose levels (Δ0.16 mmol/L, 95% CI: 0.07, 0.23) and greater odds of being obese 1.43 (95% CI: 1.01, 2.02) compared to unexposed counterparts. Non-significant associations were observed in men.

Conclusion: Reduction in birth weight due to rapid shifts in the economic environment appears to have a modest but significant association with later obesity for women while male offspring appear to be less affected by these conditions.