Vascular inflammation and sleep disordered breathing in a community-based cohort

Study Objectives: Sleep disordered breathing is associated with cardiovascular disease. The pathophysiologic mechanisms remain unclear, but enhanced vascular inflammation is implicated. We sought to evaluate the association of sleep disordered breathing with biomarkers of inflammation. Design: Crosssectional, observational. Setting: Community-based. Participants: There were 900 participants from the Framingham Heart Study site of the Sleep Heart Health Study (52% females, mean age 60 y, 23% ethnic minorities). Interventions: None. Measurements: We assessed circulating levels of nine inflammatory biomarkers in relation to polysomnographically-derived apnea-hypopnea index and hypoxemia index (% sleep time with oxyhemoglobin saturation < 90%). Multivariable models were adjusted for demographics, smoking, cardiovascular diseases, diabetes, and other potential confounders, without and with adjustment for body mass index. Results: With multivariable adjustment not including body mass index, the apnea-hypopnea index was associated with C-reactive protein, inter-leukin-6, fibrinogen, intercellular adhesion molecule-1, and P-selectin levels and hypoxemia index was associated with C-reactive protein, interleu-kin-6, and fibrinogen levels. After adjustment for body mass index, only the association of interleukin-6 with sleep disordered breathing remained significant: the adjusted mean serum interleukin-6 level was 2.93, 3.14, 3.34, and 4.62 pg/mL, respectively, in participants with apnea-hypopnea index < 5, 5-14.9, 15-29.9, and ≥ 30 events/h (P = 0.01 for trend) and 2.97, 3.01, 3.35, and 4.85 pg/mL, respectively, in participants with hypoxemia index < 0.5, 0.5-4.9, 5-9.9, and ≥ 10% of sleep time (P = 0.02 for trend). Conclusions: In a community-based sample, sleep disordered breathing is associated with higher levels of interleukin-6, a marker of myocardial infarction risk and mortality. Adiposity may mediate the increased levels of C-reactive protein, fibrinogen, intercellular adhesion molecule-1, and P-selectin observed in sleep disordered breathing.