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 mmHg or DBP between 80-85 mmHg), high normal BP group and hypertension group (SBP ≥ 140 mm Hg or DBP ≥ 90 mmHg or taking antihypertensive drugs), considering those with optimal BP (SBP120 mmHg and DBP80 mmHg) 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.