Higher parity is associated with an increased risk of type-II diabetes in Chinese women: The Singapore Chinese Health Study

Objective: The association between parity and type-II diabetes has been studied primarily in Western populations, and the findings have been inconsistent. Here, we examine whether parity was positively associated with incident type-II diabetes in Singaporean Chinese women. Design: Prospective cohort study. Setting: Singapore. Population: A total of 25 021 Singaporean Chinese women aged 45-74 years from the Singapore Chinese Health Study who were free of cancer, heart disease, stroke, and diabetes at baseline (1993-1998). Methods: Women were followed through 2004 for incident diabetes. Hazard ratios for type-II diabetes were computed across parity (of live births) categories and adjusted for baseline age, interview year, dialect, education, smoking, dietary pattern, physical activity, age at menarche, oral contraceptive use, menopausal status, hormone therapy use, and body mass index (BMI). Main outcome measure: Self-reported diabetes, as diagnosed by a doctor. Results: Over an average of 5.7 person-years of follow-up, 1294 women were diagnosed with diabetes. Before and after multivariable adjustment there was a positive graded association between parity and type-II diabetes risk (P < 0.001). In the fully adjusted model, which included adult BMI, the risk of type-II diabetes increased by 31% (from -2 to 76%), 62% (from 22 to 116%), and 74% (from 29 to 133%) for women with one or two, three or four, and five or more live births, respectively, compared with women with no live births. Moreover, in a supplementary multivariate analysis in non-diabetic women we found a positive monotonic association between parity and glycated haemoglobin (HbA1c) (P = 0.01). Conclusions: Increased parity may be a risk factor for type-II diabetes in Chinese women. More research is needed on lifestyle and physiologic factors that may explain this association.