Secular trends in heart rate, blood presure components and hypertension prevalence in young adults, 1949 to 2004: analyses of cross-sectional studies

Abstract

As few studies have comprehensively examined hemodynamic cardiovascular risk factors in youth, this study was designed to investigate the trends in blood pressure, pulse pressure, heart rate levels and hypertension prevalence in young adults between 1949 and 2004. We studied 5 240 (55% male and 45% female) students who entered Queen's University Belfast (QUB) as first year undergraduates between 1975 and 2004. These students comprised a 13% random sample of all students who entered university between 1975 and 1992, and a further 834 undergraduates (7%) who were randomly selected from all first year undergraduates who registered with University Health Centre from 2001-2004. Although original student records from 1949 to 1974 were destroyed, aggregate unadjusted findings from 1949-59 were available from previously published studies. Among students aged 16-24 we estimated the trend in mean heart rate, systolic and diastolic blood pressure and pulse pressure using linear regression analysis with year of entry as a categorical, and also as a continuous variable. χ2 test for trend was used to assess the change over time in the proportion of hypertensive (≥140/90 mm Hg) and normotensive individuals (<140/90 mm Hg). The earlier observations showed that blood pressure, pulse pressure and heart rate declined between 1949 and 1959 in both sexes. After controlling for age, BMI, height, smoking and physical activity there was strong evidence to indicate that these declines continued to the late 1980s in males (p<0.001). These trends were also generally observed in female students although diastolic blood pressure remained stable over the period. These favourable downward trends reversed thereafter, showing a deleterious increase to 2004 (p<0.001). Hypertension prevalence showed a similar pattern, declining between 1949 and late 1980s, followed by a subsequent rise to 2004 in both sexes. The decline in heart rate from 1949 observed in our study may account for some of the reduction in cardiovascular disease seen in the latter half of the 20th century. However the observed recent increase in these cardiovascular risk factors in young men and women is of concern and may have adverse implications for future patterns of cardiovascular disease.