Prenatal famine exposure and type 2 diabetes epidemics in China: a systematic review and meta-analysis

Abstract

BackgroundMany highly cited studies and reviews have interpreted the Chinese famine of 1959–61 as an important driver of current and future epidemics of type 2 diabetes in China. However, few studies used age-balanced controls, and this has caused biased results. We conducted a systematic review and meta-analysis of prenatal famine exposure and type 2 diabetes epidemics in China to examine the effect of prenatal famine with age-balanced controls. MethodsWe searched PubMed, Embase, Wanfang Data, and the Chinese National Knowledge Infrastructure databases up to January, 2019, for studies that examined the relationship between type 2 diabetes and prenatal exposure to the Chinese famine of 1959–61. From each included study, we abstracted information on the number of type 2 diabetes cases and the populations at risk for type 2 diabetes among individuals born during the famine (famine births), before the famine (pre-famine births), and after the famine (post-famine births). We compared type 2 diabetes outcomes in famine births with those of different control groups: post-famine births, pre-famine and post-famine births combined (age-balanced), and pre-famine births. Fixed-effects models and random-effects models were used to calculate summary estimates. The heterogeneity across studies was assessed. Subgroup analyses were carried out using famine severity, sex, and other reported characteristics. We examined the quality of each eligible study with the modified Newcastle–Ottawa scale. FindingsOf 3863 studies identified, 17 studies met our inclusion criteria and data from 12 studies could be used for meta-analysis. All but one study defined famine exposure based on participants' birth year alone. There were between 68 and 1372 type 2 diabetes cases in each study. When post-famine births were used as controls, we found an increased risk of type 2 diabetes (OR 1·47, 95% CI 1·20–1·80) among famine births based on the random-effects model. Using age-balanced controls, we did not find any increased risk of type 2 diabetes (1·08, 0·95–1·24). When pre-famine births were used as controls, famine was associated with a reduction in risk of type 2 diabetes (0·80, 0·66–0·96). InterpretationFrom the results of our re-analysis, it remains an open question whether the Chinese famine of 1959–61 has contributed substantially to type 2 diabetes epidemics and whether it is likely to cause or affect future epidemics. Definitions of famine exposure and selection of controls need more attention in future studies to better understand this potential association. In view of the conflicting findings, the current public health efforts for type 2 diabetes prevention and treatment in China should focus on the well-established risk factors of overweight and obesity. FundingNone.