Objective: 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.
Design and methods: 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.
Results: 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.
Conclusion: 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.