High normal blood pressure is an independent risk factor for cardiovascular disease among middle-aged but not in elderly populations: 9-year results of a population-based study

Data are conflicting and sparse regarding the impact of high normal blood pressure (BP) (systolic BP (SBP) of 130–139 mm Hg or diastolic BP (DBP) of 85–89 mm Hg) on incident cardiovascular disease (CVD) among middle-aged vs elderly population. We examined the risk of BP categories among 6273 participants⩾30 years, free of CVD at baseline, during more than 9.3 years follow-up. Cox regression analysis was used to estimate the hazard ratio (HR) of CVD for normal BP group (SBP between 120–129 mm Hg or DBP between 80–85 mm Hg), high normal BP group and hypertension group (SBP⩾140 mm Hg or DBP⩾90 mm Hg or taking antihypertensive drugs), considering those with optimal BP (SBP<120 mm Hg and DBP<80 mm Hg) as reference. During follow-up, 512 CVD events occurred. There was significant interaction between age and BP categories (P=0.028) in prediction of CVD. In multivariate analysis, HRs (95% CIs) of CVD were 1.62 (1.11–2.37) and 2.20 (1.57–3.09) for middle aged with high normal and hypertensive BP groups, respectively. Among elderly (⩾60 years), HR was 2.09 (1.36–3.21) only for hypertensive ones. High normal BP is a risk factor for incident of CVD only among middle-aged population. Furthermore, the effect of hypertension on incident CVD was stronger among younger population.