Season of birth and the risk of type 2 diabetes in adulthood: a prospective cohort study of 0.5 million Chinese adults

Abstract

Aims/hypothesis Season 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. Methods Participants 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. Results During 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.

Maternal exposure to cold spells during pregnancy is associated with higher blood pressure and hypertension in offspring later in life

“… 35,36 Furthermore, maternal exposure to cold spells and changes in nutrients and lifestyles intervenes with BP through changing DNA methylation status of the offspring. Small observed changes in methylation status can lead to large phenotypic differences that contribute to altered susceptibility to certain diseases later in life 6‐11,17,23‐27,33,36 . However, further studies are warranted to explore the underlying mechanisms that link season of birth and hypertension in adulthood.…”

“…The underlying mechanisms of hypertension are complex and multi‐factorial, where environmental factors play important roles such as exposure to low temperatures (cold spells) 2,3 . In addition, recent research has demonstrated that exposure to unfavorable environmental stimuli early in life is another important determinant of the risk of hypertension and associated conditions during adulthood 4‐6 …”

“…Season of birth, indicative of different maternal exposure to environmental factors during pregnancy, can be used to examine the associations between early‐life exposures and later‐life health outcomes, which is true since decades ago there were strong seasonal variations in nutrition and lifestyle, especially in developing countries. For instance, maternal exposure to cold spells in certain periods of pregnancy might have important correlations to consequent risk of developing diabetes mellitus in later life of offsprings 5,6 . Possible triggering factors may include decreased sunlight, physical activity, and maternal nutritional status such as vitamin D during pregnancy, which tend to change geographically and seasonally 7,8 .…”

Perinatal photoperiod associations with diabetes and chronotype prevalence in a cross-sectional study of the UK Biobank

“…Empirically, studies of time-of-year of birth associations with DM have been inconsistent for many years (Didikoglu et al 2020;Jensen et al 2015;Rothwell et al 1999;Si et al 2017;Vaiserman et al 2009;Zhao et al 2000). Recently, a season of birth association with DM (also with potential effect modification by latitude) was observed in the large China Kadoorie Biobank analysis of 0.5 million people with summer birth seemingly being protective (Si et al 2017). In contrast, no association with season of birth is described in the 0.5 million participant UK Biobank (Didikoglu et al 2020).…”

Seasonal and Monthly Patterns, Weekly Variations, and the Holiday Effect of Outpatient Visits for Type 2 Diabetes Mellitus Patients in China

“…Seasonal patterns of type 2 diabetes mellitus (T2DM) have been noted extensively. T2DM seasonal patterns were related to glucose control [1,2,3,4], temperature [5,6,7,8], Vitamin D [9,10,11,12], birth season [13,14,15,16], insulin sensitivity [17,18,19], and hypoglycemia [20,21]. Seasonal variation of type 2 diabetes exists within components of the metabolic syndrome, such as glycaemia, which is significantly higher in winter attributed to multiple causes including seasonal checkups, low temperature, and affective disorder [6].…”