Short nighttime sleepers at risk of long COVID, mental and CV diseases

Short nighttime sleepers are at higher risks of long COVID, depression and cardiovascular (CV) diseases than normal sleepers, according to three recent studies by researchers from the Chinese University of Hong Kong (CUHK).

The prevalence of sleep problems during the COVID-19 pandemic was high, at 40 percent. To investigate whether nighttime sleep duration affects the risk of long COVID in fully mRNA-vaccinated individuals, the researchers analyzed data from the Second International COVID Sleep Study (ICOSS-2) and separated 5,918 individuals into three groups by nighttime sleep duration: short (<6 hours; n=900), normal (6–9 hours; n=4,733) and long (>9 hours; n=195) nighttime sleepers. [J Clin Sleep Med 2021;17:299-313; Transl Psychiatry 2023;13:32]

Results showed that short nighttime sleepers had a higher risk of long COVID vs normal nighttime sleepers (adjusted odds ratio [aOR], 1.56; 95 percent confidence interval [CI], 1.29–1.88) after adjusting for age, sex and other factors. Short nighttime sleepers were more likely to have long COVID symptoms, including sweating and/or trouble tolerating cold or heat (aOR, 1.73; 95 percent CI, 1.45–2.07), joint and/or muscle pain (aOR, 1.67; 95 percent CI, 1.44–1.95), postexertional malaise (aOR, 1.52; 95 percent CI, 1.27–1.80), shortness of breath and/or chest pain (aOR, 1.39; 95 percent CI, 1.15–1.67), and flu-like symptoms (aOR, 1.37; 95 percent CI, 1.08–1.75) vs normal nighttime sleepers.

“We know that vaccination may have a protective effect [against] long COVID. However, the protection may be less pronounced among those sleeping <6 hours per night,” highlighted Dr Rachel Chan of the Department of Psychiatry, CUHK. “The findings further emphasize the importance of adequate sleep in reducing [the risk of] long COVID.”

In another 3-year longitudinal study (n=414), persistent eveningness and insomnia were found to be associated with a significantly increased risk of depression (aOR for eveningness, 3.07; 95 percent CI, 1.47–6.41) (aOR for insomnia, 6.53; 95 percent CI, 3.47–12.29) in Chinese adolescents. “Our findings underscore the importance of sleep and circadian factors in mood management for adolescents,” said Dr Joey Chan of the Department of Psychiatry, CUHK. [J Affect Disord 2021;294:533-542]

Additionally, a previously published UK Biobank study (n=404,044) demonstrated that short sleep duration (<6 hours) was negatively associated with arterial hypertension, atrial fibrillation, pulmonary embolism and chronic ischaemic heart disease (all p<0.001). [Eur Heart J 2021;42:3349-3357] “[The association could be explained by] common pathophysiological mechanisms, including sympathetic nervous system dysfunction, acceleration of metabolic diseases and atherosclerosis, increased inflammation, and cardiac dysfunction,” said Professor Yun-Kwok Wing, Chairman of the Department of Psychiatry, CUHK. “Therefore, extending sleep duration among short sleepers may be a promising strategy to reduce CV risks.”

Findings of the three studies echoed the theme of World Sleep Day 2023, “Sleep is Essential for Health”, which highlights the importance of obtaining adequate sleep on a regular basis to promote optimal health. “Maintaining a regular sleep-wake pattern and a pre-bedtime routine, avoiding use of electronic devices before bedtime, and creating a comfortable environment for sleep are useful sleep hygiene tips,” suggested Wing.