Association of body mass index trajectories with incidence of stroke among elderly Chinese adults: a 10-year cohort study

Background Limited data exists on relationship between body mass index (BMI) trajectory and stroke risk among elderly Chinese individuals. This study aimed to examine the association of BMI trajectory with stroke among people aged 65 years and older in China. Methods 150, 813 participants with at least three BMI measurements from 2012 to 2022 were included. Group-based trajectory modeling was used to identify BMI trajectories. Cox proportional hazards regression models were used to examine the association between BMI trajectories and incidence of stroke. Results We identified 3 (stable, slowly increased, greatly increased), 4 (slightly decreased, stable, slowly increased, sharply increased), 4 (large decreased, slightly decreased, stable, moderate increased) and 4 (substantially decreased, slightly decreased, stable, slightly increased) BMI trajectories in groups with underweight, normal weight, overweight and obesity at baseline, respectively. Taking the stable weight subgroup as the reference group, among subjects with normal weight, the adjusted hazard ratios (HRs) [95% confidence interval (CI)] were 0.93 (0.88, 0.99) for slightly decreased group, 1.07 (1.03, 1.13) for slowly increased group, and 1.12 (1.02, 1.23) for sharply increased group. Among participants with overweight, the HRs (95% CI) were 0.84 (0.75, 0.95) for large decreased group and 0.94 (0.89, 0.99) for slightly decreased group. Among participants with obesity, the HRs (95% CI) were 0.79 (0.64, 0.96) for large decreased group. Conclusion Among people aged 65 years and older, increased BMI was associated with a higher risk of stroke, while decreased BMI was related to reduced risk of stroke.