The prevalence of masked hypertension in relation to cigarette smoking in a Chinese male population

Background: Smokers may smoke cigarettes during ambulatory or home blood pressure (BP) monitoring but not clinic measurement. We investigated the prevalence of masked hypertension in relation to cigarette smoking in Chinese outpatients enrolled in a multicenter registry. Methods: Our study included 1646 men [494 (30.0%) current smokers]. We defined masked hypertension as a normal clinic SBP/DBP (<140/90 mmHg) and elevated daytime (>= 135/85 mmHg) or night-time (>= 120/70 mmHg) ambulatory or morning or evening home SBP/DBP (>= 135/85 mmHg). Results: In all men, multiple logistic regression showed that current cigarette smoking was significantly associated with daytime [prevalence 18.7%, odds ratio (OR) 1.69, 95% confidence interval 1.27-2.25,P = 0.0003] but not night-time (prevalence 27.1%,P = 0.32) ambulatory masked hypertension and associated with evening (prevalence 14.6%, OR 1.81, confidence interval 1.33-2.47,P = 0.0002) but not morning (prevalence 17.6%,P = 0.29) home masked hypertension. The associations were more pronounced for heavy smoking (>= 20 cigarettes/day) relative to never smoking for both masked daytime ambulatory (OR 1.97,P = 0.001) and evening home hypertension (OR 2.40,P < 0.0001) or in patients over 55 years of age (Pfor interaction in relation to daytime ambulatory masked hypertension = 0.005). In men with clinic normotension (n = 742), the associations were also significant (P < 0.01), particularly in those with a normal to high-normal clinic BP (n = 619,P < 0.04). Conclusion: Cigarette smoking was associated with increased odds of masked daytime ambulatory and evening home hypertension, especially in heavy smoking or older men.