24-Hour ambulatory blood pressure and C-reactive protein: a systematic review and meta-analysis

Background: Inflammation plays a key role in pathophysiology of hypertension; however the relevance of specific inflammatory mediators, such as C-reactive protein (CRP) is uncertain. We conducted a systematic literature review and meta-analysis to assess the associations between CRP levels and 24-hour blood pressure (BP) values in adult patients. Methods: We performed a systematic search of PubMed/MEDLINE, Embase, Web of Science, and Scopus for human studies published between January 2013 and June 2023. We included cross-sectional and cohort studies. We excluded studies reporting clinically significant inflammation. We calculated the Pearson’s correlation coefficients between 24-hour BP indices and the CRP levels weighted by the inverse of their variances. Results: Of 716 reports identified, 20 met eligibility criteria (10,799 participants, mean age ± standard deviation [SD] 56.1 ± 9.5 years, mean ± SD 24-hour systolic BP [SBP] 132.2 ± 14.3 mmHg, and diastolic BP [DBP] 79.3 ± 9.8 mmHg). CRP ranged from 0.14 to 10.6 mg/L, median 2.66 mg/L (interquartile range, 1.13–5.13 mg/L). In the subgroup of studies where CRP levels were ≥ 3 mg/L, a significant positive association between CRP and average 24-hour SBP (r = 0.79, P < 0.001) and DBP (r = 0.83, P < 0.001) was observed. When all studies were analyzed however, there was no correlation between CRP and neither 24-hour SBP (r = 0.18, P = 0.29), nor DBP (r = 0.27, P = 0.94). Conclusions: CRP may be an important biomarker of the relationship between inflammation and hypertension. However, the relation may not be linear throughout the entire range of CRP values. Trial Registration: International Prospective Register of Systematic Reviews (PROSPERO) Identifier: CRD42023462606.