Abstract P020: Associations of Markers of Inflammation with Nocturnal BP Dipping Status Using Two Common Dipping Definitions: the Genetic Epidemiology Network of Arteriopathy

Abstract

Background: Compared to those with natural nocturnal blood pressure (BP) decreases, those lacking nocturnal BP decreases (“non-dippers”) are at greater risk of cardiovascular disease (CVD). Substantial evidence also supports a role of chronic systemic inflammation in the pathogenesis of CVD. The purpose of this study was to examine associations of markers of inflammation with two common definitions of BP dipping status using 24-hour ambulatory blood pressure (AMBP) readings. Methods: AMBP monitoring and assays of C-reactive protein (CRP), interleukin-6 (IL-6), e-selectin, tissue inhibitor of metalloproteinase-2 (TIMP-2), and a selection of thirteen other inflammatory-pathway biomarkers were performed in 722 participants (mean age 64 [range 42-83] years, 36% men, 39% black, 83% hypertensive) in the Genetic Epidemiology Network of Arteriopathy (GENOA) Study (2001-2004). Non-dippers were classified using two common definitions: (1) nocturnal systolic and diastolic BP both decreased by <10% compared to daytime values [“dual non-dippers”, n=161 (22%)], and (2) nocturnal SBP decreased by <10% [“systolic non-dippers”, n=380 (53%)]. Logistic regressions, fit with generalized estimating equations to account for sibship clustering, yielded odds ratios (OR) of dipping status for log-transformed inflammatory biomarkers, adjusted for age, race, and sex. Results: IL-6 (range 0-37 pg/ml) was associated with dual non-dipping status (OR=1.55 [95%CI: 1.03, 2.32] p=0.035), translating into a 55% increase in the likelihood of being a dual non-dipper for every approximate doubling of IL-6. IL-6 (OR=1.63 [1.13, 2.35] p=0.009) and CRP (OR=1.35 [1.08,1.68] p=0.008) overall, as well as e-selectin (OR=0.49 [0.28, 0.87] p=0.014) and TIMP-2 (OR=0.54 [0.30,0.98] p=0.041) in hypertensive subjects were associated with systolic non-dipping status. Conclusions: These results suggest that non-dipping classification should be approached with prudence, as the two different criteria may influence conclusions about predictive marker associations. In addition, markers involved in direct versus inhibitory inflammation pathways may operate differentially across patient subgroups. Our findings support the link between inflammation and non-dipping circadian BP patterns and provide novel information on markers and definitions which may be useful for early detection and subsequent prevention of CVD.