Are inflammatory and coagulation biomarkers related to sleep characteristics in mid-life women?: Study of Women's Health across the Nation sleep study.

SLEEP DISORDERED BREATHING, SELF-REPORTED SLEEP DURATION, AND PERHAPS INSOMNIA ARE RELATED TO RISK FOR CARDIOVASCULAR DISEASE (CVD), type 2 diabetes, and obesity.1–5 Inflammatory and coagulation biomarkers are also related to risk for these conditions.6–8 It has been suggested that activation of inflammatory and pro-coagulation pathways mediates the relationships between sleep characteristics and cardiometabolic health.9,10, The purpose of the present investigation is to evaluate the cross-sectional association between sleep characteristics and circulating inflammatory and coagulation markers in an ethnically diverse sample of middle-aged women. Inflammation, blood coagulation, and immune responses are tightly linked and interdependent processes. Chronic low level inflammation contributes to coronary heart disease (CHD) through atherogenesis, plaque progression, and eventually plaque erosion and rupture.11 Moreover, atherosclerosis and vascular damage are pro-inflammatory, thereby establishing a vicious cycle. Increased activity through pro-coagulation pathways and diminished fibrinolysis has also been implicated in the pathophysiology of CHD,12,13 although it has been argued that a pre-existing hypercoagulable status is not causal.14 Rather atherosclerosis and vascular damage may cause changes in coagulation, which can feed back to inflammation. Marked acute and chronic inflammatory responses occur with infection, smoking, insulin resistance, and adiposity. Markers of inflammation include C-reactive protein (CRP), fibrinogen, and plasminogen activator inhibitor (PAI)-1. Fibrinogen also leads to increased pro-coagulant activity and plasma viscosity, factor VIIc to increased pro-coagulant activity, and both fibrinogen and PAI-1 to decreased fibrinolysis. In the present study, we evaluated the associations of biomarkers of inflammation and coagulation (CRP, fibrinogen, factor VIIc, and PAI-1) with sleep measured for 3 nights by in-home PSG studies as well as by self-report in community samples of mid-life Chinese, African American, and Caucasian women. We hypothesized that impaired sleep characteristics (short sleep duration, low continuity, low percentage of delta sleep, sleep disordered breathing, and poor sleep quality) would be associated with elevated biomarkers. We have previously reported substantial ethnic differences in sleep in our sample15 and in the biomarkers in the larger study from which our participants were drawn.16 Therefore, we also explored ethnic differences in the pattern of results. Thus, this study adds to the literature in several ways: It assessed both sleep and biomarkers of inflammation and coagulation in a comprehensive manner. It assessed sleep in the women's home increasing the ecological validity of the sleep assessments, relative to clinic-based assessments. It was based on community as opposed to clinic samples with known sleep disorders or to exceptionally healthy individuals enrolled in sleep deprivation experiments. Participants were in the menopausal transition, a time of increased sleep complaints. Finally, we tested for ethnic differences in the pattern of results, which, to our knowledge, has not been evaluated in prior research on connections between sleep and inflammation and coagulation.