Effect of Birth Year on Birth Weight and Obesity in Adulthood: Comparison between Subjects Born Prior to and during the Great Depression in Iceland

Cindy Mari Imai,Gudmundur Jonsson,Vilmundur Gudnason,Bryndis Eva Birgisdottir,Inga Thorsdottir,Thorhallur Ingi Halldorsson,Thor Aspelund,Ingibjorg Gunnarsdottir,Guoying Wang

doi:10.1371/journal.pone.0044551

Abstract

BackgroundMany epidemiological studies have linked small size at birth to adverse adult health outcomes but the relative influence of environmental exposures is less well established.MethodsThe 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).ResultsMean 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/m2, 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.ConclusionReduction 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.

Highlights

There is strong evidence suggesting risk of some metabolic disorders is set early in life and that these risks can be further heightened by factors in the external environment [1,2]
From birth year group born pre-Depression (1925–1929) to the group born during the Great Depression (1930–1934), there was a mean adjusted decrease in birth weight of 97 g for men and 70 g for women
Lower birth weight (,3.0 kg) was more common in infants with birth year exposure to the Depression compared to unexposed participants (Table 1, Panel A)

Summary

Introduction

There is strong evidence suggesting risk of some metabolic disorders is set early in life and that these risks can be further heightened by factors in the external environment [1,2]. The first weeks of pregnancy (e.g. first trimester) appear to be the most vulnerable period and those exposed to famine during this time have consistently poorer health outcomes compared to unexposed individuals [12]. These findings have been reproduced in animal studies where mimicking prenatal malnutrition led to obesity and insulin resistance in offspring [13,14]. 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

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