Influence of Sleep Quality on Antioxidant Status, Vascular Function and Physical Performance in Heart Failure

Recent evidence indicates that a reduced quality of sleep is associated with increased risk for or exacerbation of cardiovascular disease. The mechanisms are unclear. We hypothesize poor sleep, contributes to increased oxidative stress, reduced vascular function and lower exercise tolerance. PURPOSE: (1) to examine sleep quality in patients with chronic heart failure (CHF) and controls (CON), and (2) to determine the associations to antioxidant status, vascular function and physical performance. METHODS: Fifteen CHF (age=62+ or -8 yrs) and fifteen CON (age=55+ or -5 yrs) cases were examined. The Pittsburgh Sleep Quality Index (PSQI) was used to assess sleep behavior. The PSQI assesses sleep quality and disturbances over several domains. A total PSQI score >5 characterizes individuals with poor sleep quality. Brachial artery flow-mediated dilation (BAFMD) was determined using ultrasonography. Total antioxidant status was determined using commercially available kits. Six-min walk distance and isometric handgrip strength were used to evaluate physical performance. RESULTS: Total PSQI scores were higher (CHF: 8.9+ or -3.14; CON: 2.9+ or -1.8U; p=0.001) and antioxidant status lower in CHF patients (CHF: 22.52+ or -5.43; CON: 35.82+ or -10.12mM/mg; p=0.001). BAFMD (CHF: 2.98+ or -1.49; CON: 6.21+ or -1.21%; p=0.01), 6-min walk distance (CHF: 351.11+ or -87.7; CON: 438.5+ or -75.3m; p=0.001) and handgrip strength (CHF: 57.65+ or -16.5; CON: 71.67+ or -15.65kg; p=0.001) were higher in CON subjects. PSQI total score was inversely related to BAFMD (r=-0.52; p=0.03). A MANOVA revealed that individuals scoring >5 on the PSQI had significantly lower BAFMD, antioxidant status, 6-min walk distance and handgrip strength (p=0.01). CONCLUSION: The "poorer" sleep quality consistently observed in CHF is associated with lower antioxidant capacity, lower vascular function and lower physical performance.