Abstract Body (Do not enter title and authors here): Background: It is accepted that obesity increases type 2 diabetes risk. Some studies have explored associations between changes in body mass index (BMI) or waist circumference (WC), 2 indicators commonly used to assess obesity, and diabetes risk separately. However, there are few studies on the effect of change in waist-to-height ratio (WHtR), an index that has been suggested to be more strongly associated with diabetes than BMI and WC, on incident diabetes. Even fewer studies simultaneously examined the associations of change rate in the 3 indices with diabetes.
Hypothesis: WHtR change may be more strongly associated with diabetes than BMI and WC.
Aims: This study aims to investigate the change rates of BMI, WC, and WHtR in the UK adult population, and compare the effects of different adiposity indices’ changes on diabetes development.
Methods: To make facilitate quantitative comparison of BMI, WC and WHtR, we used their standardized values. Repeated measures of the 3 indices were obtained from Phase 3 (1991-94), 5 (1997-99), and 7 (2002-04) of the UK Whitehall II Study (included persons participated in at least 2 of the 3 visits). Mixed effects model was used to calculate individual change rate of the 3 indices. Non-diabetic participants at Phase 7 were then followed up for incident diabetes until Phase 9 (2007-09). We examined the prospective association between change rate of the 3 indicators and diabetes by Cox regression analysis.
Results: A total of 5,539 persons were included (mean age at Phase 3 was 49.6 years, 28.8% women). All adiposity indicators increased during Phase 3-7. The overall change rate of WHtR (0.07 SD/year) was higher than BMI (0.04 SD/year) and WC (0.06 SD/year). There were 375 non-diabetic (Phase 7) participants developing diabetes after a median follow-up period of 5.0 years. Initial WC value (HR:1.56) and WHtR value (HR:1.50) showed a stronger association with diabetes than initial BMI (HR:1.27). When the 3 indices increased at the same rate, WC change (HR:3.83, 95% CI: 2.48-5.93) had a higher risk of developing diabetes than changes in WHtR (HR:3.19, 95% CI: 2.19-4.64) and BMI (HR:2.57, 95% CI: 1.85-3.56).
Conclusions: The rate of increase over time was higher in WHtR than BMI and WC in this UK adult population. Increases in WC and WHtR were more strongly associated with incident diabetes than BMI. When the 3 indices increased at the same rate, change in WC increased a higher risk of developing diabetes relative to BMI and WHtR.