Stroke Incidence and Smoking in American Indians: An Update from the Strong Heart Study

Background/Objectives: To investigate the relationship between cigarette smoking and long-term stroke outcomes in American Indian participants of the Strong Heart Study (SHS). Methods: SHS is a longitudinal, population-based cohort study of cardiovascular disease in American Indian tribes and communities in Oklahoma, Arizona, and the Dakotas. Data were abstracted from 5802 participants without prevalent stroke, enrolled during two asynchronous sampling periods (1989-1991; 2001-2003), who underwent annual surveillance through 31 December 2021. Age- and sex-specific person-time incidence rates of stroke and their 95% CIs were calculated for each cohort. A combined analysis using shared frailty Cox proportional hazards models assessed the association of incident stroke with baseline smoking status, demographics, and other key risk factors. Results: Among participants, baseline smoking status was positive in 2220 (38.3%). Incident stroke was observed in 456 (7.9%) during a pooled median follow-up time of 19.54 years (range, 0.02-32.62) across the combined cohorts. Stroke incidence was higher among the original cohort, smokers, and older individuals. Across both cohorts, baseline current smokers had a 2.23-fold higher risk of incident stroke compared to nonsmokers (HR = 2.23, 95%CI = 1.73-2.88) and a 1.69-fold higher risk compared to former smokers (HR = 1.69, 95%CI = 1.34-2.13) after controlling for covariates. Conclusions: Smoking remains a key risk factor for stroke in American Indians. The current study extends our prior research with broader age ranges and longer follow-up in two cohorts. While American Indians have higher smoking prevalence and stroke risk, increased risk in current versus former smokers supports smoking cessation benefits and emphasizes the need for culturally tailored interventions.