Long-term body mass index variability and the risk of cardiometabolic multimorbidity in middle-aged and older adults: Insights from two prospective cohorts

Body mass index (BMI) variability is considered to be associated with an increased risk of various diseases. However, the association between long-term BMI variability and cardiometabolic multimorbidity (CMM) remains elusive, especially in middle-aged and older adults. This study aimed to explore their relationship in two prospective cohorts. Data were analyzed from the UK Biobank and the China Health and Retirement Longitudinal Study (CHARLS). CMM was defined as the coexistence of two or three cardiometabolic diseases, including diabetes mellitus, coronary heart disease, and stroke. BMI measurements from three visits were utilized to assess BMI variability. Cox regression analysis was employed to estimate the relationship between BMI variability and CMM. The incidence of CMM increased across increasing tertiles of BMI variability, particularly in overweight and obese individuals (all P for trend <0.05). This trend was absent in lean subgroups. In the UK Biobank, among participants who were overweight or obese at baseline (BMI ≥25 kg/m 2 ), those in the highest tertile of BMI variability exhibited a higher burden of CMM compared to those in the lowest tertile (HR = 2.97, 95 %CI 1.98–4.48, P < 0.001). A similar association was observed in CHARLS among individuals overweight or obese at baseline (BMI ≥24 kg/m 2 ) (HR = 1.56, 95 %CI 1.09–2.35, P = 0.017). No significant association was found between BMI variability and CMM risk in participants with normal baseline BMI. Higher BMI variability was significantly associated with an elevated risk of CMM in individuals with pre-existing overweight or obesity.