CARDIOVASCULAR MEDICINE Temperature at birth, coronary heart disease, and insulin resistance: cross sectional analyses of the British women’s heart and health study

Objective: To assess the association of mean outdoor temperature around the time of birth with insulin resistance and coronary heart disease in later life. Design: Cross sectional study. Setting: 23 British towns. Participants: 4286 women aged 60–79 years. Main outcome measures: Coronary heart disease and insulin resistance. Results: Coronary heart disease prevalence was greatest among women born during the coldest months: the age adjusted odds ratio comparing women born in the coldest quarter of monthly outdoor birth temperatures with the remaining three quarters was 1.24 (95% confidence interval (CI) 1.03 to 1.50). Cold outdoor temperature at birth was also associated with increased insulin resistance, increased triglyceride concentrations, and poorer lung function. The link between cold outdoor temperature at birth and coronary heart disease was only partly explained by known coronary disease risk factors: fully adjusted (for all measured potential explanatory and confounding factors) odds ratio 1.19 (95% CI 0.95 to 1.48). The association between cold temperature at birth and coronary heart disease was most pronounced among those whose fathers were either unemployed or in manual social classes when the participants were children, and was non-existent in those from non-manual social classes in childhood. Conclusions: Cold outdoor temperature at birth is associated with increased coronary heart disease, insulin resistance, dyslipidaemia, and poor lung function. Further research is needed to determine whether this finding reflects events occurring late in the third trimester of intrauterine growth or early in the postnatal period.