African Americans who smoke are at substantially increased risk for developing peripheral artery disease (PAD), with a dose-dependent association with subclinical disease, a Jackson Heart Study analysis showed.
After adjustment for covariates, current smokers had increased risk of ankle‐brachial index <1 (OR 2.2, 95% CI, 1.5-3.3), as well as increased risk of abdominal aortic (OR 8.4, 95% CI, 5.8-12.0) and aortoiliac calcium (OR 9.6, 95% CI, 6.7-13.7).
“After risk adjustment, current smokers had 2.2 times the likelihood of subclinical lower extremity PAD and >8 times the likelihood of a high aortic calcium burden,” Donald Clark III, MD, of the University of Mississippi Medical Center in Jackson, and colleagues reported.
PAD is three times more prevalent in African Americans than in whites, but the impact of cigarette smoking on PAD in black populations has not been well studied.
Although smoking has been strongly linked to the development of PAD in other populations, the study findings, published Jan. 23 in the Journal of the American Heart Association, confirm that smoking is a major risk factor for PAD in African Americans.
“Our findings add to the mountain of evidence showing the deleterious effects of smoking in the African American population,” Clark told MedPage Today. “We found that markers of PAD, including ankle-brachial index and aortic calcification, are highly associated with smoking in a dose-dependent manner.”
The population-based longitudinal Jackson Heart Study is the largest single-site prospective study of cardiovascular disease risk in African Americans ever undertaken, and it is also the largest study to investigate genetic factors affecting hypertension, stroke, diabetes, and other diseases that disproportionately affect blacks.
The study recruited 5,306 participants from the ages of 21 to 84 years from a tri-county area surrounding Jackson, Mississippi, who were categorized at baseline as current, past (smoked at least 400 cigarettes over their lifetime), or current smokers.
The researchers examined multivariable logistic and robust linear regression models to estimate the associations between baseline smoking status, smoking intensity, and measures of subclinical PAD (ankle‐brachial index on the first visit and aortic calcium by CT on the second visit) to yield odds ratios and β‐coefficients (estimated adjusted difference) to compare each smoking status against never smokers as the reference group.
The cohort included 3,579 (68%) never smokers, 986 (19%) past smokers, and 693 (13%) current smokers self‐identified at baseline.
When stratified by smoking intensity, study participants smoking more than 20 cigarettes daily (one pack) had higher likelihood of subclinical PAD by all of these measures compared with lower‐intensity use, suggesting a dose‐dependent relationship.
“A major finding of this study was the high degree of association between cigarette smoking, smoking intensity, and measures of subclinical PAD in the Jackson Health Study cohort,” the researchers wrote.
“In past reports, prevalence of PAD was significantly higher among blacks as compared with other racial groups, which parallels higher rates of hypertension, diabetes mellitus, and obesity. Cigarette smoking is a well‐established risk factor for PAD, but the impact of smoking on PAD has been less thoroughly investigated in blacks … The current study is among the largest analysis in blacks utilizing multiple measures of subclinical PAD, all stratified by smoking status and intensity.”
The cross-sectional design of the study, reliance on self-reporting of tobacco use, and the long (5.5 year) delay between baseline determination of smoking status and the second assessment were cited by the researchers as study limitations.
Clark said the findings from the Jackson Heart Study cohort align with those of other studies assessing the impact of smoking on PAD risk.
“Our data were unique in that this is the largest single cohort looking at cardiovascular risk factors in an African American population,” he said. “We know that the burden of disease is higher in African Americans and smoking has been strongly linked to hypertension, diabetes, and other cardiovascular diseases. I think this allows us to confidently add PAD to that list.”
The study was funded by the American Heart Association; the National Heart, Lung, and Blood Institute; Health and Human Services; and the National Institute on Minority Health and Health Disparities.
The researchers declared no relevant relationships with industry related to this study.