The J-shaped relationship between coronary heart disease and achieved blood pressure level in treated hypertension: further analyses of 12 years of follow-up of treated hypertensives in the Primary Prevention Trial in Gothenburg, Sweden.

The relationship between the blood pressure level achieved through antihypertensive treatment and the incidence of coronary heart disease (CHD) was studied in 686 middle-aged hypertensive men. The patients studied came from a random population sample and were followed-up for 12 years, yielding a total of 6563 patient-years for the study. Eighty-seven patients suffered a non-fatal myocardial infarction or died from CHD. The incidence of CHD showed a J-shaped distribution in relation to achieved treated systolic and diastolic blood pressure levels. The incidence of CHD, adjusted for entry characteristics, age, serum cholesterol, blood pressure and smoking habits, decreased with reductions in blood pressure achieved through treatment, to a level of about 150/85 mmHg, below which the incidence rate again increased. This J-shaped pattern was also observed when data from patients with pre-existing signs or symptoms of ischemic heart disease at entry were excluded. Using a quadratic term as the best fit to the observed relationship between achieved treated diastolic blood pressure level and the incidence of CHD, a Cox regression analysis showed that the nadir of the J-shaped incidence curve was at a diastolic blood pressure value of 81 mmHg. There did not seem to be any association between the absolute size of the blood pressure reduction during treatment and the incidence of CHD. Although we cannot exclude the possibility that the increased incidence of CHD in patients with a low treated blood pressure is due primarily to pre-existing but subclinical ischemic heart disease, our findings indicate that an excessive lowering of blood pressure in hypertensive patients may be harmful.(ABSTRACT TRUNCATED AT 250 WORDS)