Short-term weight change and the incidence of diabetes in midlife: results from the Australian Longitudinal Study on Women's Health

Abstract

Objective: While there is consensus that excess adiposity is strongly associated with type 2 diabetes, its relationship with weight change is less clear. This study investigates the relative impact of body mass index (BMI) at baseline and short-term (two or three year) weight changes on the incidence of diabetes.

Research Design and Methods: Prospective data were collected from a population-based cohort of mid-age women participating in the Australian Longitudinal Study on Women's Health (n=7239 for this paper). To date, participants have completed four mailed surveys (S1, 1996; S2, 1998; S3, 2001; S4, 2004). Generalised estimating equations were used to model binary repeated measures data to assess the impact of BMI at S1, and weight change (S1 to S2; S2 to S3), on three year incidence of diabetes at S3 and S4 respectively; adjusting for sociodemographic and lifestyle factors.

Results: BMI at S1 was strongly associated with the development of diabetes by S3 or S4. Compared with women who had a BMI<25, those with BMI≥25 had higher incidence of diabetes (p<0.0001), with odd ratios reaching 12.1 (95% confidence interval 7.6, 19.3) for women in the very obese group (BMI≥35). There was no association between shorter-term weight gain or weight loss on first reported diagnosis of diabetes (p=0.08).

Conclusions: Since women's risk of developing type 2 diabetes in mid-life is more closely related to their initial BMI (when aged 45-50 years) than to subsequent short-term weight change, public health initiatives should target the prevention of weight gain before and during early adulthood.