According to the Sleep Health Foundation survey in 2016 inadequate sleep, of either duration or quality, and its daytime consequences are very common in Australian adults, affecting 33-45% of adults.1 Combine these statistics with a global pandemic, disruption of normal routines, less time outside and the stress of social distancing and the unknown, and sleeplessness amongst our population has already, and is predicted to, increase significantly in the coming months. In fact the Harvard Gazette has deemed sleep to be the latest casualty of COVID-19.2,3
Sleep is important for a number of reasons, including muscle growth, tissue repair, hormone synthesis and memory consolidation. A continual lack of it is associated with cognitive consequences and a spectrum of serious health problems, including diabetes, obesity, cardiovascular disease, hypertension and more recently, Alzheimer’s disease. Chronic insomnia can also increase the risk of depression and anxiety.3,4
However, a more pertinent association in these times, is with infection. Sleep is associated with immune function, and this relationship is partially based on the physiological basis of sleep, sleep architecture, the sleep-wake cycle, cytokines and the hypothalamic-pituitary axis.5,6
It is generally concluded that sleep deprivation shifts immune activity toward cell-mediated immunity (TH1 activity) rather than toward humoral immunity (TH2 activity).7 Optimal immune function involves both of these types of immune activity. If the balance between TH1 activity and TH2 activity is altered, immune function can be compromised.
There is also a strong relationship between sleep and cytokines – the messengers of the immune system. When a person catches cold, the immune system responds with increased production of cytokines such as IL-1, IL-6, and TNF.8 Cytokines mediate changes in sleep induced by infection. In response to infection, an increase in cytokine production is associated with increases in body temperature and immune function. These changes create an unfavourable environment for the invading pathogen. Increased internal temperature not only leads to an increase in cytokine production but also to increases in metabolism and energy demand. The body tries to compensate for this loss of energy by stimulating sleep, a state in which energy expenditure is decreased. If there is a lack of sleep, the body can not regain its energy and the response is diminished.9
Studies also show that those with lack of sleep are more likely to gain infection. In one particular study of 153 healthy men and women, participants were administered nasal drops of the rhinovirus and quarantined and monitored for the development of a cold for 5 days after exposure. Those who reported a mean of less than 7 hours of sleep per night were almost 3 times more likely to acquire a cold than were those with 8 or more hours of sleep.10
Suggestions to gain a good night’s sleep during the pandemic vary from sticking to a bedtime routine to limiting exposure to electronic devices at night. These can vary in their success and may or may not be realistic solutions in a household with limited privacy and space. However there are also effective and natural ways to improve sleep outside of adjusting one’s own habits. Melatonin is a hormone that is released by the pineal gland when natural light is perceived by the retina to decrease. An increase in melatonin is associated with an increase in sleepiness.6,12
Production of melatonin gradually declines as people age, starting as early as the late twenties. However, production can drop even further due to diet and other lifestyle factors. People of all ages dealing with jet lag, shift work, or challenges to their circadian rhythm due to environment or seasonal changes may also be affected by low melatonin levels. It is also reduced by exposure to light and artificial light may also contribute to the reduction of a person’s melatonin production and increased risk of disease. A number of conditions and medications have been shown to depress melatonin levels in the blood: prostate cancer, breast cancer, autism, epilepsy, antidepressants, non-steroidal anti-inflammatory drugs (NSAIDS), beta-blockers, and calcium channel blockers for high blood pressure. Caffeine, tobacco, and alcohol use have all been associated with low melatonin levels as well.13-17
A meta-analysis of melatonin for the treatment of primary sleep disorders looked at 19 studies involving 1683 individuals. Melatonin had a statistically significant effect on reducing sleep latency and increasing total sleep time. Trials that used higher doses of melatonin and conducted over a longer duration demonstrated even greater effects on these two sleep issues, and overall sleep quality was also significantly improved in melatonin users.18
