Ankle brachial index as a predictor of cognitive impairment in the general population: Ten-year follow-up of the Edinburgh Artery Study

OBJECTIVES: To determine whether the ankle brachial index (ABI, a marker of generalized atherosclerosis) is associated with cognitive impairment after 10 years in older people. DESIGN: Cohort study (Edinburgh Artery Study). SETTING: Eleven general practices in Edinburgh, Scotland. PARTICIPANTS: Seven hundred seventeen men and women aged 55 to 74 from the general population, followed for 10 years. MEASUREMENTS: ABI measured at baseline and major cognitive functions (including premorbid function using the National Adult Reading Test, NART) tested after 10 years. RESULTS: After adjustment for age and sex, a low ABI was associated with lower scoring (bottom tertile vs top tertile) on Raven's Matrices (odds ratio (OR) = 1.6, 95% confidence interval (CI) = 1.0-2.6), Verbal Fluency (OR = 1.8, 95% CI =1.1-3.0), and Digit Symbol Test (OR = 2.3, 95% CI = 1.3-4.2), suggesting that the ABI is predictive of poorer performance in nonverbal reasoning, verbal fluency, and information processing speed. The association between ABI and the Digit Symbol Test remained significant after further adjustment for premorbid cognitive function (tested using the NART), suggesting that the ABI is also predictive of decline in information processing speed (from premorbid ability to that measured here in older age). CONCLUSION: The ABI may be useful in identifying older individuals at higher risk of cognitive impairment. In the future, preventive measures developed to target individuals with a low ABI should consider measures to reduce vascular-related cognitive decline as well as cardiovascular events, in an effort to reduce the incidence and consequences of subsequent cognitive impairment and dementia.