Effect of cigarette smoking on the J-shaped relationship between treated blood pressure and cardiovascular disease. Hypertension Follow-up Group of the Japan Federation of Democratic Medical Institutions.

It is known that a J-shaped relationship exists between treated blood pressure and the incidence of cardiovascular disease. To determine the relationship, an assessment was made of 6,825 patients aged 50-75 years who were receiving antihypertensive drugs. Blood pressures were averaged from five readings that were measured at the time of entry and during the preceding year. Current smoking status was ascertained by interview. During the mean follow-up period of 2.7 years (18,562 patient-years), the 241 incidences of cardiovascular disease (CVD), which occurred including cerebrovascular disease, were classified into 156 strokes, 59 myocardial infarctions, 18 congestive heart failures, 2 aortic aneurysmal ruptures, and 6 sudden deaths. In smokers, the sex, and age-adjusted incidence of CVD per 1,000 patient-years was 24*, 13, 24*, 40**, according to the treated systolic blood pressure (SBP) subgroups, i.e., < 140, 140-149, 150-159, and > or = 160 mmHg, respectively (*P < 0.05, **P < 0.005 compared with 140-149 mmHg). A J-shaped relationship with a dip at the middle SBP (140-149 mmHg) was recognized between treated SBP and CVD. Similar J-shaped curves were also present in each male age bracket, 50-59, 60-69, 70 yrs and older, and in women. However, in nonsmokers, the incidence in relation to SBP was 7, 9, 10, 17, respectively, (P < 0.01 compared with 140-149 mmHg), showing a positive linear relationship between SBP and CVD. These findings suggest that cigarette smoking leads to the J-shaped relationship between treated SBP and the incidence of CVD.