The relationship between the trajectory of body mass index changes over a long lifecycle and the risk of all-cause mortality in patients with cardiovascular disease: the NHANES longitudinal cohort study

Background The relationship between body mass index (BMI) changes over a long lifecycle and the risk of all-cause mortality among patients with cardiovascular disease (CVD) remains understudied. This study aims to investigate the association between BMI changes (from age 25 to after 50) and the risk of all-cause mortality in CVD patients. Methods This study leveraged data from the National Health and Nutrition Examination Survey (NHANES) 2001–2018 and the National Death Index (NDI) to construct a longitudinal cohort. Employing weighted multivariable Cox regression and Restricted Cubic Spline (RCS) analyses, we evaluated both the linear and nonlinear associations between BMI (at age 25 and after 50), its changes, and the risk of all-cause mortality among patients with CVD. Furthermore, we stratified the participants based on their BMI categories at these two time points to determine the relationship between different BMI trajectory patterns and all-cause mortality risk. Results A total of 2304 CVD patients were included in this study. During a median follow-up of 68 months, 774 participants died. The lowest risk of mortality was observed when BMI was 19.61 at age 25 and 26.55 after the age of 50. The impact of BMI change between these two time points on all-cause mortality risk exhibited a segmented effect with a threshold of 8.27. Specifically, when the change in BMI exceeded 8.27, it was positively associated with all-cause mortality risk [HR = 1.16, 95%CI=(1.00, 1.33)]. This relationship was most pronounced among CVD patients who were overweight at both ages 25 and after 50. Conclusion Among CVD patients, a U-shaped relationship is observed between BMI changes over a long lifecycle and the risk of all-cause mortality, where both excessive increases and decreases in BMI contribute to an elevated risk. BMI management strategies should be tailored to individual BMI trajectories, rather than solely focusing on weight loss.