Long COVID as a risk factor for hypersomnolence and fatigue: insights from the 2nd International Covid Sleep Study Collaboration (ICOSS-2)

Background Hypersomnolence, defined as excessive daytime sleepiness (EDS), excessive quantity of sleep (EQS), sleep inertia, and fatigue reduce quality of life. We assessed associations of the COVID-19 pandemic, infection without long-term sequalae (short COVID, SC), and long COVID (LC) on hypersomnolence and fatigue in a large population across different countries. Methods As part of an online questionnaire (ICOSS-2), we assessed EDS via the Epworth Sleepiness Scale (ESS), fatigue via Fatigue Severity Scale (FSS), and sleep duration at night and per 24 hours. We also assessed the associations with EDS, sleep inertia, fatigue and napping by their frequencies, during the pandemic in COVID-negative, SC and LC participants. Results The final cohort comprised 13,656 participants (69.1% women, 42.7±16.6 years), with 12.4% classified SC and 7.5% LC. ESS scores were higher in LC (9.16, 95% CI [8.78, 9.53]) compared to SC (7.26, [6.97, 7.55]) and COVID-negative (6.53, [6.43, 6.63]). LC also had higher odds of ESS>10 (OR 1.58, [1.18,2.09]). FSS scores were higher in LC (median 51, IQR 39-59) than SC (34, 25-44) and COVID-negative (35, 25-45), with LC having 2.22 higher odds of severe fatigue. LC cases also reported more EQS (≥10/24h) than COVID-negative. Worsening of EDS, fatigue, sleep inertia, and napping was reported during pandemic to a greater extent in LC. Conclusions LC was associated with higher levels of hypersomnolence and fatigue than in SC or COVID-negative participants, highlighting the need for interventions and future research focusing on sleep symptoms and their relation to long-term health outcomes.