Cigarette smoking and subtypes of uncontrolled blood pressure among diagnosed hypertensive patients: Paradoxical associations and implications

Abstract

BACKGROUND: Isolated uncontrolled systolic blood pressure (SBP), uncontrolled systolic- diastolic blood pressure (BP), and isolated uncontrolled diastolic blood pressure (DBP) are subtypes of uncontrolled BP. The associations of smoking with uncontrolled BP subtypes among diagnosed hypertensive patients are unknown. METHODS: Seven thousand eight hundred twenty-nine subjects aged 18 years or over with diagnosed hypertension were selected from the National Health and Nutrition Examination Survey with stratified multistage clustered sampling design. Weighted logistic regressions were conducted to estimate odds ratios (ORs) with 95% confidence intervals (CIs) of uncontrolled BP subtypes related to smoking status. Weighted multiple regression models were used to examine the association of smoking with levels of SBP, DBP, and pulse pressure. RESULTS: The average age of the study sample was 60.3 ± 0.3 years. 54.2% ± 0.7% were females. Compared to nonsmokers, current smokers were 22% less likely to have uncontrolled BP (OR: 0.78, 95% CI: 0.64-0.94, P = 0.01), and 21% less likely to have isolated uncontrolled SBP (OR: 0.79, 95% CI: 0.64-0.97, P = 0.02). Average DBP was 1.5 mm Hg lower (95% CI: -2.8 to -0.2 mm Hg, P = 0.02) in current smokers than in nonsmokers. Average DBP was 0.9 mm Hg lower (95% CI: -1.7 to -0.03 mm Hg, P = 0.04) in former smokers than in nonsmokers. Current smoking and former smoking were not associated with risk of uncontrolled systolic-diastolic BP and isolated uncontrolled DBP. CONCLUSIONS: Paradoxical associations between current smoking and SBP, uncontrolled BP and isolated uncontrolled SBP were shown among hypertensive patients. The explanation for these associations is currently unknown. No cause-effect relationships should be assumed.