Body mass index, waist circumference, and the risk of type 2 diabetes mellitus: implications for routine clinical practice.

BACKGROUND: Current guidelines for assessing the risk of developing type 2 diabetes mellitus (DM) recommend using the patient's body-mass index (BMI) as a primary measure. Waist circumference measurement is recommended for overweight or obese patients only (BMI > or = 25).

METHODS: We studied the interaction between BMI and waist circumference with respect to the risk of developing type 2 DM in a cohort of 9753 men and 15491 women, aged 35 to 65, who participated in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam. The statistical analysis was performed with multivariable-adjusted Cox proportional hazard regression.

RESULTS: During a mean follow-up interval of 8 years, type 2 DM was newly diagnosed in 583 men and 425 women. A statistically significant interaction was found between BMI and waist circumference with respect to the risk of type 2 DM (p<0.0001). The positive association between waist circumference and diabetes risk was stronger in persons with lower BMI. The relative risk (RR) of developing type 2 DM among persons of low or normal weight (BMI < 25) who had a large waist circumference was at least as high as that among overweight persons (BMI 25-29.9) with a small waist circumference: for the first case, the RR was 3.62 [1.67-7.83] in men and 2.74 [1.52-4.94] in women; for the second case, the RR was 2.26 [1.51-3.37] in men and 1.40 [0.61-3.19] in women (The figures in square brackets are 95% confidence intervals). These relative risks were calculated in comparison to the risk among persons of low or normal weight (BMI < 25) with a small waist circumference.

CONCLUSION: These findings imply that the waist circumference is an important additional piece of information for assessing the risk of type 2 DM, particularly among persons of low or normal weight.