Development of Blood Pressure and the Incidence of Hypertension in Men and Women Over an 18-year Period

Abstract

The objective of this study was to determine the factors that influence diastolic blood pressure (DBP) and the incidence of hypertension. In 1977, DBP and cardiovascular risk factors were measured in 7092 men and women. In 1995, 2335 subjects participated at a second screening. Those patients already under hypertension treatment in 1977 were excluded. The DBP tracking was studied in subjects not under hypertension treatment during the study. Hypertension was defined on two ways in the analysis: under current hypertension treatment or a DBP > 95 mmHg measured at rescreening in 1995. Forty-seven percent of the subjects with a DBP < 75 mmHg in 1977 remained in the same category of DBP in 1995, and 7% had become hypertensive. Of the 75–84 mmHg group in 1977, 40% stayed in the same category in 1995 and 15% became hypertensive. Of the 85–94 mmHg category, 30% stayed in the same category and 30% became hypertensive in 1995. Of the highest category in 1977 (> 95 mmHg), 64% were still in that category in 1995. Baseline DBP in 1977 had the highest predictive value for future DBP. Weight gain over the years increased the risk for future hypertension: in contrast, there was no risk at a low DBP without weight gain. There is no need for regular check-ups for those patients with a low DBP who experience no weight gain. Borderline DBP (85–95 mmHg), together with weight gain, increases the risk of development of hypertension. The risk was especially high for men in the lower socioeconomic class.

Introduction

A persistent elevation of blood pressure (BP) is a known risk factor for cardiovascular disease. The relationship between BP and cardiovascular disease and mortality is quantitative: the higher the BP, the greater the risk [1]. Although repeated measurement is needed to classify patients correctly [2], one single BP reading has a predictive value for future blood pressures. In primary care, one BP measurement is often the first step regarding further monitoring, as long-term follow-up of patients with high-normal BP can prove to be quite time consuming, given that many patients remain normotensive 3, 4. Prospective studies have shown that higher initial blood pressures increase the risk of acquiring hypertension in the future. In the Medical Research Council (MRC) trial between 12% and 15% of persons with diastolic blood pressure (DBP) of at least 90 mmHg developed hypertension within 3 to 5 years [5].

A study of tracking of blood pressure over time will give information about the natural course of blood pressure and the risk for developing hypertension [6]. In men there is evidence that young adults in the top of blood pressure distribution are likely to stay in the same class over time [7]. From the ages of 20 to 45 years, systolic blood pressure (SBP) hardly rises in men and women, whereas after that age, the rise in SBP is steeper in women than in men, resulting in higher SBP in older women 8, 9. DBP increases more constantly in adult life to reach a maximum value around the age of 50 years in men and 60 years in women. From a preventive point of view, it would be helpful to be able to predict, to a certain extent, whether an adult patient will become hypertensive over the years, as such knowledge could eliminate the need for regular BP screenings and thus result in a significant time saving. Insight into the contribution of the determinants of BP increase will provide an opportunity for preventive advice in individuals. For instance, it is known that a high body weight in adolescents is related to higher blood pressures in adult life 6, 10 but the predictive value of this risk factor for the development of hypertension is not very high, so screening for high blood pressure is advised in all adults [12]. Obesity and weight gain have been proved to be an important factor in the development of hypertension in adults 13, 14, 15. Hypertensive patients were found to have higher levels of modifiable cardiovascular risk factors, especially in the lower socioeconomic class [16]. However, an investigation into the changes in BP in individuals requires longitudinal data. The Framingham heart study showed data of the risk for acquiring hypertension, but it did not look at those not developing hypertension [11]. Former BP tracking studies were carried out in selected populations 6, 7 or in untreated patients, participating in hypertension treatment trials 3, 4. No data in The Netherlands investigating BP changes in individuals over time are known to us.

In 1977, cardiovascular risk factors were measured in 7092 patients aged 20–50 years, as part of an intervention project. In 1995, when these patients were between 38 and 68 years of age, a part of the cohort of 1977 was invited to undergo a reevaluation of their cardiovascular risk factors. The aim of the present study was to investigate how BP developed over 18 years in patients not undergoing hypertension treatment in 1977, relative to advancing age and other factors that could have an influence on the course of BP and the onset of hypertension.