Joint trajectories of abdominal obesity and systolic blood pressure are associated with incident stroke in two prospective cohorts

BACKGROUND: Abdominal obesity and elevated systolic blood pressure (SBP) are established stroke risk factors, yet their joint longitudinal patterns and combined associations on stroke incidence remain unclear. We aimed to identify joint trajectory groups of waist-to-height ratio (WHtR) and SBP and evaluate their associations with incident stroke. METHODS: We included 5,128 participants from the Health and Retirement Study (HRS, United States, 2006-2018) and 4,869 from the English Longitudinal Study of Ageing (ELSA, England, 2004-2012). Group-based multi-trajectory modeling jointly classified WHtR and SBP trajectories. Cox regression with progressive covariate adjustment estimated hazard ratios (HRs) for incident stroke. Subgroup and sensitivity analyses were performed. RESULTS: Four joint WHtR-SBP trajectory groups were identified in both cohorts. Compared with the "Non-abdominal obesity & Normal SBP" reference group, the group characterized by the highest WHtR yet only moderately elevated SBP had the greatest stroke risk in both the HRS (HR = 2.61, 95%CI 1.85-3.67) and ELSA (HR = 2.34, 95%CI 1.34-4.10), followed by the group with abdominal obesity and high SBP (HRS: HR = 2.49; ELSA: HR = 2.03). Joint exposure analysis confirmed additive associations, with co-occurring exposures conferring the greatest risk (HRS: HR = 2.68; ELSA: HR = 2.53). Associations were stronger among participants without hypertension. CONCLUSIONS: Abdominal obesity and elevated SBP show additive associations on incident stroke through distinct joint trajectory patterns, consistently replicated across two independent cohorts. Severe abdominal obesity conferred the highest stroke risk even without markedly elevated blood pressure, suggesting that longitudinal monitoring of abdominal adiposity alongside blood pressure management may improve stroke risk stratification in aging populations.