Longitudinal body mass index exposure-based threshold to prevent mortality for populations with type 2 diabetes mellitus

The long-term body mass index (BMI) threshold to prevent mortality among aging individuals with type 2 diabetes mellitus (T2DM) remains unclear. We quantify BMI exposure using two metrics: the percentage of time BMI above target range (TAR) and the percentage of time BMI within target range (TTR). In a cohort of 3,708 adults aged ≥40 years with T2DM and at least 5 BMI measurements across 4 years, 1,020 deaths occurred during a median 5-year follow-up. Sustained BMI ≥27 kg/m² (TAR) is positively associated with an increased risk of mortality. Furthermore, longer sustenance of BMI within the range of 18.5-26.9 kg/m² (TTR) is associated with dose-response survival benefits for all-cause, cardiovascular, and cancer mortality, respectively (all p < 0.05). The association is further validated in the China Health and Retirement Longitudinal Study cohort. These findings support that the threshold for increased mortality risk is sustained exposure to BMI ≥27 kg/m² in middle-aged and elderly adults with T2DM.