Variously on this site I have reported on the health benefits of getting enough sleep (see here for a relevant article). My attention was drawn to a study published this week which assessed the relationship between sleep time and susceptibility to the common cold in a group of about 150 male and female adults . In this study, the subjects were asked to record their sleep time for 14 consecutive days. After this, the individuals were quarantined, and had the common cold virus (rhinovirus) administered to them via some nasal drops. The individuals were monitored for the development of cold symptoms until 5 days after the drops were administered.
The results showed that those who slept for an average of less than 7 hours of sleep each night were about 3 times more likely to contract a full-blown cold compared to those sleeping 8 hours a night or more.
The researchers who conducted this study also assessed the relationship between ‘sleep efficiency’ (the percentage of time spent in bed during which subjects were actually asleep) and susceptibility to infection. Here again, they found a significant association: individuals with less than 92 per cent sleep efficiency were 5 and a half times more likely to develop signs of an infection compared to those with a sleep efficiency of 98 per cent or more.
The researchers looked at other factors that might explain why lower levels of sleep and lower sleep efficiency is associated with increased susceptibility to infection including antibody levels to the cold virus before administration of the virus, season and health practices. None of them explained the association, which makes the case for a real association between sleep habits and immunity a real one. On top of this, there is research which has found that inducing sleep deprivation in subjects can also induce changes that suggest weakening of the immune system.
Taken together, the research suggests that adequate sleep is important for optimal immune functioning and resistance to infection. It’s another good reason to see sleep not as a waste of time, but an important investment in our health and wellbeing.
1. Cohen S, et al. Sleep habits and susceptibility to the common cold. Arch Intern Med. 2009;169(1):62-7.