Changes in sleep patterns during COVID-19 lockdown: correspondence.

Dear Editor,

We read the article entitled “Changes in sleep patterns of college students in Israel during COVID-19 lockdown, a sleep diaries study” [1]. Lan et al. mentioned that “A lockdown period affects sleep–wake behavior: during lockdown people sleep duration is increased and their sleep onset is delayed. Nevertheless, the circadian preference of individuals is conserved across conditions. [1].” We agree that the effect of COVID-19 lockdown on sleep is interesting. A basic concern on the present study is on the reliability of the sleep diaries study. If there is a good control of bias, sleep diary might be acceptable for assessment of duration but not other parameters [2]. Nevertheless, there might also be an association with the phase of the outbreak in the study setting. When the outbreak period changes, there might be adjustment to the problem and it might affect the characteristics of sleep [3].