A body shape index trajectories and cognitive function among older hypertensive patients: a national cohort study

BACKGROUND: While several cross-sectional studies have suggested an association between a body shape index (ABSI) and cognitive decline, the relationship between longitudinal ABSI patterns and cognitive outcomes among older hypertensive patients remains unclear. This study aimed to investigate the association between ABSI trajectories and cognitive outcomes in this population using a longitudinal cohort design. METHODS: Data were obtained from the China Health and Retirement Longitudinal Study (CHARLS), with ABSI measurements collected in 2011, 2013, and 2015. Group-based trajectory modeling (GBTM) was used to identify the distinct ABSI trajectories. Cox proportional hazards models and linear mixed-effects models were applied to evaluate the association between ABSI trajectories and cognitive function among older hypertensive patients. RESULTS: A total of 1,065 older hypertensive participants were included in the study (572 males, 53.7%; 493 females, 46.3%). Three ABSI trajectory groups were identified: moderate-stable (n = 602, 56.5%), low-rapid-rising (n = 144, 13.5%), and high-slightly-increasing (n = 319, 30.0%). After adjusting for potential confounders, there was borderline evidence of effect modification by sex for incident low cognitive performance defined by a Z-score cutoff (P for interaction = 0.046). Compared with low-rapid-rising trajectory group, hazard ratio point estimates were higher in women (moderate-stable trajectory group: HR = 1.57, 95% CI 0.81-3.03; high-slightly-increasing trajectory group: HR = 1.83, 95% CI 0.94-3.58) but lower in men (moderate-stable trajectory group: HR = 0.78, 95% CI 0.48-1.27; high-slightly-increasing trajectory group: HR = 0.63, 95% CI 0.36-1.09), although sex-stratified estimates were imprecise, with confidence intervals crossing the null. In mixed-effects models of global cognitive Z-scores, baseline cognition was similar across groups; moderate-stable trajectory group showed a less steep decline than low-rapid-rising trajectory group (moderate-stable trajectory group×time: β = 0.05, 95% CI: 0.00-0.10), whereas high-slightly-increasing trajectory group was similar, with no evidence of sex modification of slopes. CONCLUSIONS: Long-term ABSI trajectories showed heterogeneous associations with cognitive outcomes in older hypertensive patients, with potential sex-related heterogeneity for incident low cognitive performance. Defining incident events by first crossing a Z-score cutoff may capture earlier cognitive vulnerability before clinically diagnosed impairment, offering a prevention-relevant perspective on longitudinal changes in ABSI among older adults with hypertension. However, sex-specific estimates were imprecise, and replication in larger, independent cohorts is warranted.