Body mass index and mortality in people with and without diabetes: A UK Biobank study

Abstract

Background and aims: To investigate the association of body mass index with all-cause, cardiovascular and cancer mortality in individuals with and without diabetes.

Methods and results: We used data on 490,852 participants from the UK Biobank, with linkage to national mortality data between 2006 and 2016. Using Cox regression, we calculated hazard ratios (HRs) and 95% confidence intervals (95%CI) for all-cause, cardiovascular and cancer mortality within body mass index categories in people with and without diabetes adjusting for potential confounders. 24,789 (5.0%) participants reported having diabetes at baseline. Over a median follow-up of 6.9 years, 13,896 participants died, of which 1800 had diabetes. Compared with normal body mass index (18.5-24.9 kg/m²), mortality risk in the overweight group (25.0-29.9 kg/m²) was 33% lower in people with diabetes (HR 0.67, 95%CI 0.62-0.73) and 12% lower in participants without (HR 0.88, 95%CI 0.85-0.90). For class I obesity (30.0-34.9 kg/m²), mortality risk was 35% lower in participants with diabetes (HR 0.65, 95%CI 0.59-0.71) and 5% lower in participants without (HR 0.95, 95%CI 0.91-0.99). For class III obesity (≥40 kg/m²), there was a 10% non-significant lower mortality risk compared to normal body mass index in people with diabetes (HR 0.90, 95%CI 0.77-1.05); in contrast, the risk was 29% higher in people without diabetes (HR 1.29, 95%CI 1.13-1.45). Similar patterns were observed for cardiovascular mortality but not for cancer mortality.

Conclusion: The impact of obesity on the risk of mortality was dependent on the presence of diabetes: for the same level of obesity, mortality risk was higher in people without diabetes compared to those with diabetes.

Keywords: Body mass index; Diabetes; Mortality; Observational study; UK Biobank.