Nocturnal Hypertension Status and C-Reactive Protein Levels Before and After AEXT

Abstract

C-Reactive Protein (CRP) is an inflammatory biomarker linked to endothelial dysfunction, resulting hypertension, and cardiovascular events. 24-hr ambulatory blood pressure monitoring (ABPM) is the gold standard for diagnosing hypertension, with recent evidence showing a superior predictive value of asleep nighttime values, in particular, for cardiovascular outcomes. PURPOSE: To assess whether circulating CRP levels differ between nighttime hypertensives and normotensives and examine the ability of exercise training to affect CRP levels. METHODS: Non-smoking, middle-to-older age, sedentary African Americans underwent an aerobic exercise training (AEXT) program for 24 weeks. Various modes of AEX were included, with intensity progressing up to 60% VO2 max. Participants underwent 6 weeks of dietary stabilization and were required to maintain a constant weight for the study’s duration. CRP and blood pressure (BP) were measured from fasted blood samples and 24-hour ABPM, respectively, before and after the AEXT program. Upon study completion, subjects were divided into groups based on average asleep ABPM values (O’Brien et al 2013) and baseline circulating CRP levels. RESULTS: At baseline, normotensive subjects had significantly lower circulating CRP than those classified as hypertensives based on nighttime systolic BP (2.95 vs 4.74 mg/L, p<.01). Although there was no difference between normotensives and hypertensives classified as at low (<1mg/L) or high (>3mg/L) risk for cardiovascular disease based on CRP levels, there was a difference in circulating CRP between groups at average risk (p<.05). CRP did not significantly decrease (p=.095), however, after 6 months of AEXT the hypertensive group experienced a significantly greater decrease in CRP than the normotensive group (p =.01). CONCLUSIONS: Our results suggests that nighttime hypertensive status may correspond to cardiovascular disease risks predicted by the classic biomarker CRP. Nocturnal SBP may be a discriminating additive factor to consider for health by those at average risk for future events by CRP levels. For both hypertensives and normotensives, AEXT may alter CRP, with hypertensives likely to see a greater effect. Supplementary studies are needed to examine the relationship between additional variables and nocturnal hypertension.