Abstract-The objective of the present study was to examine the hypothesis that baseline heart rate (HR) predicts subsequent blood pressure (BP) independently of baseline BP. In the multicenter longitudinal Coronary Artery Risk Development in Young Adults study of black and white men and women initially aged 18 to 30 years, we studied 4762 participants who were not current users of antihypertensive drugs and had no history of heart problems at the baseline examination (1985)(1986). In each race-sex subgroup, we estimated the effect of baseline HR on BP 2, 5, 7, and 10 years later by use of repeated measures regression analysis, adjusting for baseline BP, age, education, body fatness, physical fitness, fasting insulin, parental hypertension, cigarette smoking, alcohol consumption, oral contraceptive use, and change of body mass index from baseline. The association between baseline HR and subsequent systolic BP (SBP) was explained by multivariable adjustment. However, HR was an independent predictor of subsequent diastolic BP (DBP) regardless of initial BP and other confounders in white men, white women, and black men (0.7 mm Hg increase per 10 bpm). We incorporated the part of the association that was already present at baseline by not adjusting for baseline DBP: the mean increase in subsequent DBP was 1.3 mm Hg per 10 bpm in white men, white women, and black men. A high HR may be considered a risk factor for subsequent high DBP in young persons. (Hypertension. 1999;33:640-646.)Key Words: heart rate Ⅲ blood pressure Ⅲ hypertension Ⅲ regression analysis Ⅲ race T hough evidence has been accumulating that heart rate (HR) is a correlate of blood pressure (BP), HR has not been the central focus of epidemiological investigations of BP. 1 Yet numerous cross-sectional or case-control studies show an independent relationship between HR and hypertension 14,[17][18][19] or with both systolic BP (SBP) and diastolic BP (DBP). 8,9,13,16,22,23 Prospective studies 2-7,10 -12,15,20,21,24,28 on the association between HR and subsequent BP are inconsistent. Many, but not all, lose statistical significance after adjustment for baseline BP, the most potent predictor of subsequent BP. Important confounders such as physical activity or fitness are not considered in these studies. Thus, whether HR affects BP level remains uncertain. Also, cross-sectional HR-BP associations have been found to be different in blacks compared with whites. 7,11,27 We tested the following hypotheses in young black and white participants in the Coronary Artery Risk Development In young Adults (CARDIA) study: 1. Baseline HR is an independent predictor of subsequent BP after adjustment for baseline BP and other confounders. 2. Race-sex is an effect modifier for the association between HR and subsequent BP.
MethodsCARDIA is a multicenter longitudinal epidemiological study of the determinants of cardiovascular risk factors during young adulthood. Methods are described in detail elsewhere. 29,30 Briefly, 5115 black and white women and men aged 18 to 30 years at b...