Does cigarette smoking exacerbate the effect of blood pressure on the risk of cardiovascular and all-cause mortality among hypertensive patients?

OBJECTIVE: To examine the risk of cigarette smoking on cardiovascular disease (CVD) and all-cause mortality among hypertensive patients.
METHODS: We conducted a prospective cohort study among 36,943 hypertensive patients aged at least 40 years. Data on smoking and other variables were obtained in 1991 and follow-up evaluation was conducted in 1999-2000.
RESULTS: During a median follow-up of 8.2 years, we documented 7194 deaths among 36 943 hypertensive patients. Compared with never-smokers, the multivariate-adjusted relative risks (MRRs) [95% confidence intervals (CIs)] for CVD mortality were 1.19 (1.07, 1.31) and 1.33 (1.23, 1.45) for those who smoked 0.1-19 pack-years and at least 20 pack-years (P for linear trends <0.001 for all). A similar pattern was observed for all-cause mortality. A dose-response association between pack-years smoked and risk of CVD and all-cause mortality (all P ≤ 0.01) was found among the SBP groups (140-159, 160-179, and ≥ 180 mmHg), DBP groups (<90, 90-94, and 100-109 mmHg), and pulse pressure groups (50-59, 60-69, and ≥ 70 mmHg). In addition, compared to never-smokers with stage 1 hypertension, MRRs of CVD and all-cause mortality for those who smoked at least 20 pack-years with stage 3 hypertension were remarkably increased to 3.06 (2.64, 3.54) and 2.51 (2.24, 2.80), respectively.
CONCLUSIONS: Smoking not only significantly increased the risk of CVD and all-cause mortality among hypertensive groups, but the synergistic effect on the risk of CVD and all-cause mortality existed between cigarette smoking and blood pressure category. Therefore, apart from hypertension management, smoking cessation should be an essential component for preventing deaths related to smoking.