The effect of previous strokes on the relationship between ankle-brachial index determinations and incident strokes: A population-based, longitudinal prospective study in older adults

Abstract

Objective Abnormal ankle-brachial index (ABI) determinations may be associated with an increased risk of incident strokes. However, the impact of previous strokes in this relationship is unknown. We estimated the role of previous strokes on the association between abnormal ABI determinations and incident stroke risk in community-dwelling older adults. Methods Atahualpa residents aged ≥60 years received ABI determinations, cardiovascular risk factors assessment, and brain MRIs. ABIs were classified as abnormal if ≤0.9 or ≥1.4. Incident strokes were diagnosed by a certified neurologist with the aid of a post-event MRI. Poisson regression models were fitted to estimate stroke incidence rate ratio (IRR) according to categories of ABI. Results Analysis included 389 participants (mean age: 68.2 ± 8.1 years). Eighty-six persons (22%) had abnormal ABI determinations. Incident strokes occurred in 38 (9.8%) individuals after a mean follow-up of 6.1 ± 1.9 years. Abnormal ABIs were associated with incident strokes in unadjusted analyses ( p = 0.002) as well as in a Poisson regression model adjusted for demographics and clinical covariates (IRR: 2.57; 95% C.I.: 1.29–5.13), but not when the model was adjusted for neuroimaging covariates (IRR: 1.46; 95% C.I.: 0.67–3.20). Interaction models showed that having both abnormal ABI and non-lacunar strokes at baseline made the individual 9.7 times more likely to have an incident stroke (95% C.I.: 3.87–24.4). The risk was reduced to 2.2 (95% C.I.: 0.96–5.13) for those who only had an abnormal ABI. Conclusions An abnormal ABI is associated with a doubling the risk of incident strokes, but its importance is superseded by history of non-lacunar strokes.