Introduction: Laws banning smoking in indoor public places have been associated with reductions in second-hand smoke exposure and cardiovascular disease among non-smokers. Second-hand smoke exposure has been associated with hypertension in prior studies. However, it is unknown whether smoke-free policies are associated with changes in blood pressure.
Hypothesis: We tested the hypothesis that living in an area with a smoke-free policy banning smoking in restaurants, bars, and/or other workplaces is associated with reductions in systolic and diastolic blood pressure among non-smokers.
Methods: Longitudinal data from 2,896 non-smoking participants of the Coronary Artery Risk Development in Young Adults (CARDIA) Study (aged 18-30 at enrollment, 1985-2011, 14,193 person-exam-years) were linked to state, county, and local 100% smoke-free policies in bars, restaurants, and/or non-hospitality workplaces based on participants’ census tract of residence at each exam. Fixed-effects linear regression estimated associations of each type of smoke-free policy (restaurant, bar, workplace) with within-person changes in systolic and diastolic blood pressure (SBP and DBP). Models adjusted for time-varying covariates: exam year (categorical), socio-demographic (education, income, marital status), health-related (body mass index, total physical activity, alcohol use), and policy (state cigarette tax, self-reported ban on smoking in their workplace) covariates, and interactions of baseline covariates (age, sex, race, field center) with exam year to account for differences in blood pressure patterns that were associated with these characteristics (p<0.05 for all interactions). Blood pressure values were adjusted to reflect antihypertensive medication use (+10 mmHg for SBP, +5 mmHg for DBP for those on medication).
Results: At baseline, mean SBP was 110.5 mmHg and mean DBP was 69.3 mmHg. By year 25, a majority of participants were exposed to smoke-free policies in restaurants (1,759 of 2,264, 78%), bars (1,536 of 2,264, 68%), and other workplaces (1,518 of 2,264, 67%). Smoke-free policies were associated with within-person reductions in SBP and DBP in fully adjusted models (expressed as average change between exams in mmHg). Mean reductions in SBP were -0.77 (95% CI: -1.51, -0.02) for restaurant policies, -0.73 (95% CI: -1.54, 0.08) for bar policies, and -0.79 (95% CI: -1.51, -0.08) for workplace policies. Mean reductions in DBP were -0.67 (95% CI: -1.27, -0.06) for restaurant policies, -0.54 (95% CI: -1.20, 0.11) for bar policies, and -0.86 (95% CI: -1.44, -0.28) for workplace policies.
Conclusions: Smoke-free policies in restaurants and other workplace are associated with within-person reductions in systolic and diastolic blood pressure among non-smokers. These results suggest an additional health benefit of these policies beyond those previously described in the literature.