24 h non-invasive ambulatory blood pressure monitoring: do the number of recordings per hour and/or ways of analyzing day and night matter?

OBJECTIVE: To analyze whether the number of blood pressure registrations per hour and/or different ways of defining day and night have any influence on the result of ambulatory blood pressure monitoring. DESIGN AND METHODS: The study used blood pressure data from 40 normotensive subjects (20 men) and 40 (20 men) treated hypertensive patients who had undergone 24 h non-invasive ambulatory blood pressure monitoring twice (on a work day and a non-work day), three recordings per hour being made. Calculations were made based on all recordings and with one and two recordings per hour randomly removed. The definition of night was the subject's own (from going to bed until getting up), and an arbitrary designation of 2200 h-0600 h. RESULTS: The mean blood pressure (systolic/diastolic and standard deviation) over 24 h showed no significant difference between calculations based on three, two or one blood pressure registrations per hour in either hypertensives or normotensives, nor was there any significant difference when the same kind of calculation for day and night was made based on the subject's own statement or on arbitrary dividing lines. The between-patient standard deviation increased, albeit marginally, with fewer registrations. Individual comparisons revealed a difference over 24 h of 8.4/6.7 mm Hg between three and one registrations per hour in one hypertensive patient during a non-work day. All the others had lesser and very small differences. CONCLUSION: An analysis of our data revealed no major differences in mean blood pressure if one, two or three recordings per hour were used. Arbitrary dividing lines for day and night or according to the individual's own statement did not have any major effect on the result. This must be considered to be an advantage when data from different studies are compared or pooled. It may, however, be wise to perform recordings no less than every 30 min when evaluating individual patients.

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)

Mortality and morbidity in relation to systolic blood pressure in two populations with different management of hypertension: The Study of Men Born in 1913 and the Multifactorial Primary Prevention Trial.

Total mortality and cardiovascular disease (CVD) mortality and morbidity during 10 years of follow-up in relation to systolic blood pressure (SBP) at entry were compared between a random sample of 7455 men, aged 47-54 years at entry, in whom multifactorial risk-factor intervention including intense efforts to detect and treat hypertension had been performed [the Primary Prevention Trial (PPT)], and a similar population (from an observational study) in which intervention, on CVD risk factors was kept to a minimum (the Study of Men Born in 1913). Total mortality, CVD mortality, coronary heart disease (CHD) and stroke incidence increased with SBP in both populations, but levelled off above the cut-off point for antihypertensive treatment in the population subjected to multifactorial CVD risk factor intervention. In this population total mortality was reduced by 30%, CVD mortality by 37%, CHD morbidity by 13% and stroke morbidity by 30% above the cut-off point for blood pressure intervention compared with the incidence predicted from the observational study. These findings indicate that multifactorial intervention, and especially antihypertensive treatment, have preventive effects in the hypertensive part of the middle-aged male population.