The association of the ankle-brachial index with incident coronary heart disease: the Atherosclerosis Risk In Communities (ARIC) study, 1987-2001.
BACKGROUND
Peripheral arterial disease (PAD), defined by a low ankle-brachial index (ABI), is associated with an increased risk of cardiovascular events, but the risk of coronary heart disease (CHD) over the range of the ABI is not well characterized, nor described for African Americans.


METHODS
The ABI was measured in 12186 white and African American men and women in the Atherosclerosis Risk in Communities Study in 1987-89. Fatal and non-fatal CHD events were ascertained through annual telephone contacts, surveys of hospital discharge lists and death certificate data, and clinical examinations, including electrocardiograms, every 3 years. Participants were followed for a median of 13.1 years. Age- and field-center-adjusted hazard ratios (HRs) were estimated using Cox regression models.


RESULTS
Over a median 13.1 years follow-up, 964 fatal or non-fatal CHD events accrued. In whites, the age- and field-center-adjusted CHD hazard ratio (HR, 95% CI) for PAD (ABI<0.90) was 2.81 (1.77-4.45) for men and 2.05 (1.20-3.53) for women. In African Americans, the HR for men was 4.86 (2.76-8.47) and for women was 2.34 (1.26-4.35). The CHD risk increased exponentially with decreasing ABI as a continuous function, and continued to decline at ABI values > 1.0, in all race-gender subgroups. The association between the ABI and CHD relative risk was similar for men and women in both race groups. A 0.10 lower ABI increased the CHD hazard by 25% (95% CI 17-34%) in white men, by 20% (8-33%) in white women, by 34% (19-50%) in African American men, and by 32% (17-50%) in African American women.


CONCLUSIONS
African American members of the ARIC cohort had higher prevalences of PAD and greater risk of CHD associated with ABI-defined PAD than did white participants. Unlike in other cohorts, in ARIC the CHD risk failed to increase at high (>1.3) ABI values. We conclude that at this time high ABI values should not be routinely considered a marker for increased CVD risk in the general population. Further research is needed on the value of the ABI at specific cutpoints for risk stratification in the context of traditional risk factors.
Weatherley
Beth D
BD
Duke Clinical Research Institute, Duke University Medical Center, P,O, Box 17969, Durham, NC 27715, USA. beth.weatherley@duke.edu
Nelson
Jeanenne J
JJ
Heiss
Gerardo
G
Chambless
Lloyd E
LE
Sharrett
A Richey
AR
Nieto
F Javier
FJ
Folsom
Aaron R
AR
Rosamond
Wayne D
WD
D001741:Black or African American / Q000706:statistics & numerical data; D000842:Ankle / Q000098:blood supply*; D050197:Atherosclerosis / Q000175:diagnosis / Q000453:epidemiology; D001916:Brachial Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D015331:Cohort Studies; D015897:Comorbidity; D003327:Coronary Disease / Q000175:diagnosis / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016491:Peripheral Vascular Diseases / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D016012:Poisson Distribution; D016016:Proportional Hazards Models; D018570:Risk Assessment; D016019:Survival Analysis; D018608:Ultrasonography, Doppler; D014481:United States / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data