Abstract
Aims/hypothesisSeason of birth as a surrogate for potential environmental exposure during fetal development and early postnatal life has shown an inconsistent association with adult type 2 diabetes in white populations living in high-latitude regions. The present study aimed to examine the association between birth seasonality and risk of adult type 2 diabetes in Chinese individuals living across wide regions of low latitude and lower to middle latitude.MethodsParticipants from the China Kadoorie Biobank were enrolled during 2004–2008 and followed up until 31 December 2013. After excluding participants with cancer, heart disease, stroke and diabetes at baseline, the present study included 189,153 men and 272,058 women aged 30–79 years. We used multivariable Cox proportional hazards model to estimate the HR and 95% CI.ResultsDuring a median follow-up of 7.2 years (3.3 million person-years), we documented 8784 incident cases of type 2 diabetes. In the whole cohort, compared with summer-born participants, the adjusted HRs (95% CIs) were 1.09 (1.02, 1.16), 1.08 (1.02, 1.15) and 1.09 (1.02, 1.15) for those who were born in Spring, Autumn and Winter, respectively. The association was consistent in both men and women and across subgroups defined by residence and lifestyle factors later in life.Conclusions/interpretationIn this large prospective study, participants born in summer had a lower risk of adult type 2 diabetes compared with other seasons of birth, suggesting exposures in early life with some degree of seasonal variation might influence the risk of adult diabetes.
Highlights
In 2014, there were 387 million people living with diabetes and 4.9 million deaths attributable to diabetes worldwide [1]
We prospectively examined the association between season of birth and risk of type 2 diabetes in adulthood in the China Kadoorie Biobank (CKB; see the electronic supplementary material [ESM] for a list of members of the CKB Collaborative Group) study of 0.5 million adults, a population living across wide regions of low latitude and lower to middle latitude
In multivariable-adjusted models, the season of birth was significantly associated with the risk of incident type 2 diabetes
Summary
In 2014, there were 387 million people living with diabetes and 4.9 million deaths attributable to diabetes worldwide [1]. There is a growing interest in the contribution of prenatal environmental exposure to the risk of type 2 diabetes in adulthood. It has been suggested that adverse environmental influences during critical periods of prenatal growth could permanently change the structure and function of organs and tissues, leading to increased susceptibility to the development of type 2 diabetes in later life [3]. In addition to special famine events, the season or month of birth often serves as a surrogate for potential environmental exposure during perinatal life. A few studies conducted in white populations living in relatively high-latitude regions have examined the association between the season or month of birth and type 2 diabetes in adulthood, with mixed results [9,10,11]
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