A longitudinal study on the change in sleep across three waves of the COVID-19 outbreaks in Hong Kong

In the year 2020, Hong Kong experienced four COVID-19 epidemic waves. The present study aimed to examine the transition of sleep disturbances and explore its associated factors across the later three epidemic waves. Among the 1138 respondents who participated in an online survey at the second wave (T1, April 2020), 338 and 378 participants also completed a follow-up at the third (T2, August 2020) and fourth waves (T3, December 2020), respectively. Participants completed the Insomnia Severity Index and an investigator-designed questionnaire regarding potential factors associated with sleep change such as perceived risk of being infected, economic stress, and confidence in the government and health care professional. Sample of this study were mainly female (67.7%), married (50.3%), young adults (54.2%) with tertiary education (81.6%). Maintaining normal sleep was the most prevalent trajectory of sleep of all three waves (50.5%), followed by persistent insomnia (17.2%) and remitted insomnia (9.0%). Besides female, older-age and lower education level, the results showed that increment in worry about family being infected (adjusted risk ratio, RR = 1.28), perceived interference of daily lives (adjusted RR = 1.19), and economic distress (adjusted RR = 1.24) were significantly associated with the development of clinical insomnia during the three epidemic waves. These factors were also associated with worsening of other sleep parameters. Insomnia being persistent across the three waves of COVID-19 outbreaks was common. Increasing economic distress, daily interference, and worry about family members being infected were associated with an increasing risk of clinical insomnia across the three COVID-19 outbreaks.