Abstract P309: Prevalence of Low Ankle-Brachial Index among Individuals with Non-High Risk for Coronary Heart Disease: Data from the National Health and Nutrition Examination Survey 1999–2004
Background: Abnormal ankle-brachial index (ABI) is prospectively associated with coronary heart disease (CHD) independent of traditional Framingham risk scores (FRS) variables. Two-thirds of CHD events occur in individuals with lower FRS (<20%). Evaluating the role of supplemental risk assessment with ABI among those subjects may have significant public health impact. We explore prevalence of abnormal ABI among the low-intermediate risk US population according to sex, age and race.
Methods: We included 5035 cardiovascular disease-free, nonpregnant, nondiabetic individuals aged from 40 to 79 years from the National Health and Nutrition Examination Survey 1999–2004, representing approximately 75 million US adults. FRS was used to estimate participants’ 10-year risk for CHD, and two risk categories were defined as low (> 6%) and intermediate (6% – < 20%). Individuals with risk estimates ≥ 20% were excluded from this analysis. Abnormal ABI was defined as ABI < 0.9. Participants were categorized into younger ages (40–64) and older ages (65–79). The number needed to screen (NNS), which is the number of people within each stratum that needed to be screened to detect one person with abnormal ABI was used to assess the yield of screening for ABI.
Results: Mean age was 53.1 years, with 45% (2261/5035) male, 19% (978/5035) non-Hispanic Black. Weighted prevalence of an abnormal ABI was 1.63% (61/2261) in men and 3.78% (138/2774) in women, corresponding to 2.1 million US adults aged 40 and above. Abnormal ABI was observed in 0.4% (2/714) and 2.4% (59/1488) in men (NNS=357 and 26) of those with low and intermediate risk, and 2.8% (85/2248) and 9.4% (53/526) in women (NNS=26 and 10), respectively. Older participants have higher prevalence of abnormal ABI than younger both in men (4.4% (29/435) vs. 1.8% (32/1826), NNS=15 and 57) and women (7.5% (63/748) vs. 2.9% (75/2026), NNS=12 and 27). Non-Hispanic Blacks have higher prevalence of abnormal ABI than other races in men (Black: 3.1% (21/458) vs. White: 1.6% (29/1144) and others: 0.9% (11/659)) as well as in women (Black: 7.1% (40/520) vs. White: 3.7% (64/1379) and others: 2.3% (34/875)).
Conclusions: Among individuals at low-intermediate predicted 10-year CHD risk in US population, we observed concordance between abnormal ABI prevalence and FRS risk strata. The yield of screening and possibility of identifying abnormal ABI cases is highest in those with intermediate risk, especially older ages, non-Hispanic blacks and females.
- © 2012 by American Heart Association, Inc.