A socio-historical hypothesis for the diabetes epidemic in Chinese - Preliminary observations from Hong Kong as a natural experiment

It has been hypothesized that the emerging epidemic of diabetes in economically transitioning or recently transitioned populations is due to mismatch between developmental and mature environments. We took advantage of migration within an ethnically homogenous population to investigate this hypothesis, and the potentially modifying role of postnatal growth conditions, proxied by greater height. We used multivariable logistic regression in a population-based cross-sectional study from 1994 to 1996 of 2,341 long-term Hong Kong residents aged 25-74 years, either born in contemporaneously developed Hong Kong or migrants from economically undeveloped Guangdong. Migrant status was not associated with clinically diagnosed diabetes, odds ratio 1.05 (95% confidence interval 0.69-1.58) in adult migrants compared to Hong Kong-born natives and 1.22 (0.83-1.80) in preadult migrants, adjusted for age, sex, socio-economic position, and lifestyle. However, the association of diabetes with migrant status varied with height, suggesting a potentially complex relationship between indicators of prenatal and postnatal nutritional exposures. Compared to tall Hong Kong-born natives, the odds ratio of diabetes was 2.36 (1.20-4.61) in tall migrants, 1.94 (1.07-3.53) in short Hong Kong-born natives, but 1.04 (0.48-2.23) in short adult migrants. Additionally adjusting for body mass index and waist-hip ratio had little effect, apart from attenuating the association between short height and diabetes prevalence in Hong Kong-born natives. Whether the current epidemic of diabetes is a long-standing effect of such mismatch or a "first-generation through effect" generated by rapid economic development causing disproportionate growth remains to be determined.