Considering vertebral artery stenosis in young healthy heavy smokers

Abstract

Cigarette smoking is a well-known risk factor of atherosclerosis. In a large cross-sectional cohort study, about 48.7% of young strokes were attributable to current smoking. In Iran, in different subpopulations, cigarette smoking ranges from 0.4% to 41%, and the extremes stand for the adolescence and students. A recent meta-analysis revealed one-fifth of Iranian male adults smoke. Cranial arterial stenosis is a major determinant of ischemic stroke. Young stroke is a major health concern in Iran. Previous studies have shown a higher incidence and higher in-hospital mortality in comparison with western countries. Regarding stroke risk factors, smoking seems to be the frequent well-documented and modifiable risk factor in young stroke. Despite an increasing rate of cigarette smoking in Iran, its serious adverse effects on cranial atherosclerotic changes have not been investigated and need probing in healthy young adults. The objective of this study was to investigate the potential risk of heavy cigarette smoking and asymptomatic cranial arterial stenosis in healthy young volunteers. The study was approved by the ethics committee of Iran University of Medical Sciences (IUMS). We recruited subjects ranging between 18 and 45 years of age, using telephone surveys. Two hundred subjects completed informed consent and participate in our study. Participants had normal blood pressure, did not have diabetes, and had no history of hyperlipidemia, or family history of premature vascular disease, and drug use. Regarding the information obtained from the questionnaire, subjects who smoked more than 10 pack-years (more than 20 cigarettes per day for 10 years) are considered heavy smokers. We found 17 cases (15 males, 2 females) as healthy heavy smokers on the basis of medical history and physical examination and lab results, all without any evidence of cardiovascular events. Sixty-eight healthy non-smoker controls (fourfold) were randomly chosen among 183 remaining samples. All cases underwent carotid Color Doppler Ultrasonography (USG). The hemodynamics of vertebral and carotid artery was evaluated by means of pulsatility index (PI) and mean diameter of arteries. No degree of carotid luminal narrowing was observed in cases. A complete vertebral Color Doppler USG was attempted in all healthy cases and healthy nonsmoker controls (85 subjects). Proximal vertebral artery (VA) was the most common site of atherosclerotic changes in young healthy heavy smokers. Table 1 shows the arterial diameter of proximal VA and PI for cases and controls. The multivariate logistic regression model was set up to examine the effect of smoking, age, sex in case and control groups. We provided the bivariate analysis for each factor. The odds ratio (OR) for age was 0.99 with 95% confidence interval (CI) (0.92–1.07) and for sex, it was 0.96 with 95% CI (0.32–2.83). In the bivariate analysis for cigarette smoking, we found OR1⁄4 10.34 with 95% CI (2.19–48.78). In the Middle East and Iran, the incidence of stroke is increasing and its burden has become a major public health concern. Because of neglected symptoms of vertebrobasilar ischemia, the prevalence of VA disease due to atherosclerotic changes often remains undiagnosed. Approximately 20–25% of posterior ischemic stroke are due to VA stenosis. Our results highlighted that heavy cigarette smoking is highly associated with proximal VA stenosis changes in healthy subjects and appears in younger age 37.2 (SD 4.3). Our findings are consistent with a risk factor analysis study in Iranian population comparing the anterior and posterior circulation strokes. This study showed that smoking was a major risk factor for posterior circulation stroke. These results could be inferred crucial by investigating the association between heavy