Smoking as a modifier of the systolic blood pressure-induced risk of cardiovascular events and mortality: a population-based prospective study of middle-aged men

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Abstract
To examine to what degree smoking habits modulate the relationship between systolic blood pressure (SBP) and risk for cardiovascular morbidity (first event) and mortality in middle-aged men. In all, 22 444 middle-aged men were recruited from a population-based screening study (mean attendance rate 71%). Risk factor intervention was offered to about 20% of participants. Subjects were followed in local and national registers for cardiovascular morbidity and mortality during more than 17 years of follow-up. Life-style variables were investigated at baseline, including smoking habits. Event rates were calculated in relation to quintiles (Q1-Q5) of baseline SBP in untreated subjects, subdivided into categories of smoking habits, but also for 915 previously known, treated hypertensive (tHT) patients at baseline. We found an increasing incidence of first cardiovascular event (CE) with increasing SBP levels, ranging from 63.5 CE/10 000 person-years (Q1) to 62.3, 70.5, 82.3 and 115.1 CE/10 000 person-years (Q2-Q5). The corresponding figure in tHTs was 153 CE/10 000 person-years. If further subdivided into smokers/ex-smokers/non-smokers, the relative risks (RR) of smokers were 1.9 [95% confidence interval (CI): 1.5-2.4], 2.1 (1.8-2.5), 2.3 (1.8-2.9), 1.8 (1.5-2.1), and 1.7 (1.5-2.0) compared to present non-smokers, in relation to SBP (Q1-Q5). In tHTs the RR was 1.4 (1.1-1.8). Cardiovascular mortality rates differed in relation to SBP and smoking habits, from 40.3 (present non-smokers) and 70.7 (smokers) deaths/10 000 person-years in Q1, to 54.2 and 134.0 deaths/10 000 person-years in Q5. In tHTs the corresponding figures were 81.6 and 149.4 deaths/10 000 person-years, respectively. No difference in risk was found for never-smokers compared to ex-smokers in relation to SBP. The risk in moderate/heavy smokers ( 10 cigarettes/day) compared to other smokers (<or= 10 cigarettes/day) was significantly ( 0.005) increased only in Q5. Increasing systolic blood pressure levels in middle-aged men is associated with an increasing risk of future cardiovascular events and mortality, an association modified by smoking habits. Patients with treated hypertension in the 1970-1980s were also at an increased risk in spite of healthcare efforts. This calls for a more comprehensive multiple risk factor approach for the management and reduction of cardiovascular risk in these patients.

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