[Body mass index, waist circumference and waist-to-height ratio associated with the incidence of type 2 diabetes mellitus: a cohort study].

Objective: To investigate the association between body mass index (BMI), waist circumference (WC), waist-to-height ratio (WHtR), and the incidence risk of type 2 diabetes mellitus (T2DM).
Methods: In total, 20 194 participants ≥18 years old were selected randomly by cluster sampling from two township (town) of the county in Henan province from July to August of 2007 and July to August of 2008 and the investigation included questionnaires, anthropometric measurements, fasting plasma glucose, and lipid profile examination were performed at baseline; 17 236 participants were enrolled in this cohort study. 14 720 (85.4%) were followed up from July to August 2013 and July to October 2014. Finally, 11 643 participants (4 301 males and 7 342 females) were included in this study. Incidence density and Cox proportional hazards regression models were used to evaluate the risk of T2DM associated with baseline BMI, WC, WHtR, and their dynamic changes.
Results: After average of 6.01 years following up for 11 643 participants, 613 developed T2DM and the incidence density was 0.89 per 100 person-years. After adjusted for baseline sex, age, smoking, drinking, family history of diabetes, as well as the difference of fasting plasma-glucose (FPG), total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C), systolic blood pressure (SBP), diastolic blood pressure (DBP) between baseline and follow-up, Cox Proportional-Hazards regression analysis indicated that T2DM risk of baseline BMI overweight group, BMI obesity group, abnormal WC group and abnormal WHtR group were significantly higher than that of the corresponding baseline normal groups , and the incidence risk of T2DM reached the highest for those whose baseline BMI, WC and WHtR were all abnormal, the corresponding HR (95%CI) were 2.05 (1.62-2.59), 3.01 (2.33-3.90), 2.34 (1.89-2.90), 2.88 (2.21-3.74), 3.32 (2.50-4.40), respectively. Whether baseline BMI/WC was normal or not, T2DM risk increased if baseline WHtR was abnormal, and the HR (95%CI) of baseline normal BMI/abnormal WHtR group, baseline abnormal BMI/abnormal WHtR group, baseline normal WC/abnormal WHtR group, baseline abnormal WC/abnormal WHtR group were 1.88 (1.29-2.74), 3.08 (2.34-4.05), 2.15(1.53-3.00), 3.22 (2.45-4.23), respectively. The analysis for dynamic changes of BMI, WC, and WHtR indicated that in baseline normal WC or WHtR group, T2DM risk increased when baseline normal WC or WHtR developed abnormal at follow-up, and the corresponding HR (95%CI) were 1.79 (1.26-2.55), 2.12(1.32-3.39), respectively. In baseline abnormal WC or WHtR group, T2DM risk decresed when baseline abnormal WC or WHtR reversed to normal at follow-up, and the corresponding HR (95%CI) were 2.16 (1.42-3.29), 2.62 (1.63-4.20), respectively.
Conclusion: BMI, WC, and WHtR were associated with increased T2DM risk. The more abnormal aggregation of BMI, WC, and WHtR presents, the higher T2DM risk was. T2DM risk could be decreased when abnormal WC or WHtR reversed to normal.