Estimating Burden of Disease among blind individuals with Non-24-Hour Sleep-Wake Disorder

Purpose: To quantify the burden of disease in blind patients with Non-24-Hour Sleep- Wake Disorder (N24HSWD), utilizing longitudinal sleep diary data. N24HSWD is a circadian disorder characterized by a cyclical pattern of aberrant circadian and sleep-wake cycles that are associated with increased frequency of sleep episodes during the school/work day hours. Daytime sleep episodes will decrease the opportunity of school/work participation significantly impacting the quality of life of the patient. Methods: We used the day time sleep diary data from a period of approximately 90 days in blind individuals with a sleep complaint, which were identified from a group of blind individuals with N24HSWD (n=121) and a control group of blind individuals without N24HSWD (n=57). Results: N24HSWD patients had more frequent and longer episodes of daytime sleep as compared to a control group. N24HSWD patients also had significantly fewer healthy days, defined by daytime sleep free days (DSFD), as compared to the control group. Conclusion: Daytime sleep free day (DSFD) is a useful and specific measure of disease burden in patients with N24HSWD and it is predicted to be correlated with the standardized HRQOL-4, Healthy Days measurement.