Abstract
Purpose: To quantify the burden of disease in blind patients with Non-24-H 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 would be predicted to decrease the opportunity for school/work participation, significantly impacting the quality of life of the patient.Methods: We used the sleep diary data of daytime sleep from a period of ~90 days in blind individuals that presented with a sleep complaint. These subjects 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. Using duration of daytime sleep as a surrogate for defining a healthy or unhealthy day, N24HSWD patients also had significantly fewer healthy days, defined by daytime sleep free days (DSFD), days without a sleep episode between 9:00 a.m. and 5:00 p.m, 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.
Highlights
Non-24-Hour Sleep-Wake Disorder (N24HSWD) is a rare circadian disorder that affects both sighted and blind patients but is highly prevalent among individuals who are totally blind and lack light perception [1]
DSFD is expressed as daytime sleep free days in a 30-day period. This transformation allows us to compare this measure with unhealthy days as measured by the Centers for Disease Control (CDC) Behavioral Risk Factor Surveillance System Health Related Quality of Life (HRQOL-4) questionnaire in the general population [6]
The patients in this study are a sequential cohort of blind patients with a sleep complaint that participated in a clinical program, TABLE 1 | Characteristics of the control and Non-24-Hour Sleep-Wake Disorder subjects from the Safety and Efficacy of Tasimelteon (SET) [1] study
Summary
Non-24-Hour Sleep-Wake Disorder (N24HSWD) is a rare circadian disorder that affects both sighted and blind patients but is highly prevalent among individuals who are totally blind and lack light perception [1]. The endogenous timing system has a beat cycle of a little longer than 24 h and in blind individuals, it is around 24.20 h [2] This endogenous circadian system is reset every day through the perception of light through the retina, maintaining a Estimating Burden of Disease, Non-24 periodicity of 24 h [1]. In this study we aim to quantify the burden of disease in N24HSWD patients, by utilizing longitudinal sleep diary data and transforming them into a surrogate measurement of healthy days in a given 30-day period. We refer to this measurement as daytime sleep free days (DSFD), measured through different thresholds of sleep between 9:00 a.m. and 5:00 p.m. DSFD is expressed as daytime sleep free days in a 30-day period. While further studies will be needed to validate the DSFD as a measure of disease burden in N24HSWD, our work establishes DSFD as a specific tool to allow for the study of the impact of N24HSWD in patients with this severe and debilitating chronic condition
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