Abstract
INTRODUCTION: Chronic hypertension is associated with left ventricular hypertrophy. Recent evidence suggests that secondhand smoke (SHS) exposure is associated with chronic hypertension, so we sought to examine the relationship between secondhand smoke exposure and electrocardiographic left ventricular (LV) mass among non-smokers. METHODS: This analysis included 4982 non-smoker participants from the Third National Health and Nutrition Examination (NHANES-III). Non-smoking was defined by self-report and serum cotinine ≤10 ng/mL, a biomarker for tobacco exposure. SHS exposure was defined as serum cotinine level ≥1 ng/mL. LV mass was estimated using an electrocardiographic model developed and applied in NHANES-III then validated in the Cardiovascular Health Study. Multivariable linear regression was used to examine the cross-sectional association between SHS exposure (vs no exposure) with estimated LV mass index. In similar models, we also examined the associations of LV mass index across quartiles of serum cotinine (reference group, 1st quartile) and in subgroups stratified by age, race, sex, hypertension, and obesity. RESULTS: About 9.8% (n=489) of the participants were exposed to SHS. Exposure to SHS was associated with an estimated 2.9 g/m(2) increase in LV mass index, with a dose-response relationship between higher serum cotinine and LV mass index. These results were consistent in men and women, Whites and non-Whites, elderly and non-elderly, and those with and without hypertension. Significant effect modification was present among obese individuals with an estimated 4.8 g/m(2) increase in LV mass index (interaction p=0.01). CONCLUSIONS: In a racially diverse sample of non-smokers, SHS is associated with increased LV mass with a dose-response relationship between level of exposure and LV mass. Effect modification was present among obese individuals. These findings underscore the harmful effect of passive smoking on the cardiovascular system and highlight the need for more restrictions on smoking in public areas, especially in countries or regions with less-stringent public health policies.