Subjective sleep alterations in healthy subjects worldwide during COVID-19 pandemic: A systematic review, meta-analysis and meta-regression

Objective: We conducted a systematic review and meta-analysis to provide an update on sleep quality in different world areas and better characterize subjective sleep alterations during the COVID-19 pandemic. Considering gender distribution and specific pandemic-related parameters, we also intend to identify significant predictors of sleep problems. Methods: Six electronic databases were searched from December 2019 to November 2021 for studies investigating sleep during COVID-19 employing the Pittsburgh Sleep Quality Index, the Medical Outcomes Study Sleep, the Insomnia Severity Index or the Epworth Sleepiness Scale. Random-effects models were implemented to estimate the pooled raw means of subjective sleep alterations. Also, we considered the role of several pandemic-related parameters (i.e., days from the first COVID-19 case, government stringency index, new cases for a million people, new deaths for a million people) by means of meta-regression analyses. Results: A total of 139 studies were selected. The pooled mean of the global Pittsburgh Sleep Quality Index score (PSQIgen) was 6.73 (95% CI, 6.61–6.85). The insomnia severity index score was reported from 50 studies with a pooled mean of 8.44 (95% CI, 7.53–9.26). Subgroup analyses confirmed that most subcategories had poor sleep quality and subclinical insomnia. Meta-regressions showed that PSQIgen was predicted by days from the first COVID-19 case and government restrictions with a negative slope and by female gender with a positive slope. The government stringency index was positively correlated with the direct subjective evaluation of sleep quality. Conclusions: We found an overall impaired sleep and widespread subthreshold insomnia during the COVID-19 pandemic. The female percentage seems to be the best predictor of impaired sleep quality, consistently to the available literature. Noteworthy, sleep alterations were inversely associated with governmental restrictions and decreased during the pandemic. Our results give a contribution to critically orienting further studies on sleep since COVID-19 pandemic.