Age differences in the risk of diabetes incidence according to body mass index level in Japanese women: BMI and diabetes in women

SummaryObjectiveTo investigate the age differences in the risk of diabetes incidence according to body mass index (BMI).MethodsFor an average of 10.3 years, this study prospectively followed a cohort of 4725 women aged 30–69 years without diabetes at a baseline health check-up conducted between April 1990 and March 1992. Diabetes onset was identified by fasting and random plasma glucose level, HbA1c or the medical treatment for diabetes by questionnaire. We stratified the subjects according to age (30–39, 40–49, 50–59 and 60–69 years), and calculated the risk of diabetes incidence according to BMI categories (<18.5, 18.5–22.9, 23.0–24.9 and ≥25.0 kg/m2) using the Cox proportional hazards model.ResultsDuring 48,866 person-years of follow-up, 392 subjects developed diabetes. Using the normal group as the reference, the HR (95% CI) for diabetes incidence was elevated in obese women of all ages, ranging from a high of 4.72 (1.79–12.40) for women who were 30–39 years of age, to a low of 1.54 (1.02–2.33) for those who were 50–59 years of age.ConclusionsThe risk of diabetes incidence according to BMI is different among different age groups of Japanese women. Obese is a strong risk factor for diabetes incidence among women of all ages, and especially among young adults.