Relationship of predominantly mild current smoking to out-of-office blood pressure in a community sample in Africa

Objectives: As the impact of mild smoking on blood pressure (BP) is uncertain, we assessed the relationship between predominantly mild current smoking and out-of-office BP and the effect of angiotensin-converting enzyme (ACE) genotype on this relationship in a community sample of black African ancestry.

Methods: In 689 participants randomly recruited from an urban, developing community of black African descent, we assessed smoking habits, out-of-office (24-h), and in-office conventional and central (applanation tonometry) BP, and ACE insertion (I)/deletion (D) variant genotype.

Results: A total of 14.5% (n=100) were current smokers, the majority being mild (72%, 7.4 ± 4.6 cigarettes/day). Despite current smokers having only modest increases in in-office (P<0.05) and similar central aortic BP values as nonsmokers, current smokers had higher unadjusted (P<0.005-P<0.0005) and multivariate adjusted 24-h SBP/DBP (mmHg; smokers=123 ± 15/76 ± 10; nonsmokers=118 ± 14/72 ± 9; P<0.005-P<0.0005) than nonsmokers, effects that were DD genotype-dependent (P<0.005 for interaction) and replicated in sex-specific groups, nondrinkers, and in overweight and obese. Current smoking was second only to age in the quantitative impact on 24-h DBP. Smoking 4.6 cigarettes per day (one standard deviation) translated into increases in 24-h SBP (mmHg) of 2.12 [confidence interval (CI)=1.77-2.47] in all participants and 3.62 (CI=3.13-4.12) in participants with the DD genotype. The risk of uncontrolled 24-h BP was increased in smokers as compared to nonsmokers (adjusted odds ratio=1.87, CI=1.02-3.41, P<0.05), an effect that was enhanced in participants with the DD genotype (adjusted odds ratio=4.01, CI=1.59-10.09, P<0.005).

Conclusion: Mild current smoking is independently associated with an appreciable proportion of out-of-office BP in a black African community, an effect that is ACE genotype-dependent.