In a resent study, “Sleep Habits and Susceptibility to the Common Cold.” Dr Sheldon Cohen, of the Department of Psychology at Carnegie Mellon University in Pittsburgh, Pennsylvania, and his colleagues found that poor sleep to be a predictor of low immunity.
Researchers paid healthy male and female volunteers $800 to have cold viruses sprayed up their noses. The subjects were kept under close observation for signs of a cold during the day before their exposure and for 5 days afterwards while they waited in a hotel to see if they got sick. Study participants who slept fewer than seven hours a night, and who spent more of that time awake, were nearly three times more likely to develop a cold than people who had eight hours or more of undisturbed sleep.
Before the 14 days of monitoring, each participant also underwent a “pre-challenge” examination, where the researchers obtained information about potential confounders such as virus-specific antibody levels in their blood, demographics, body mass index, psychological variables and health behaviors.
The results showed that:
- The less a person slept, the more likely he or she was to develop a cold (there was a graded association between infection rate and average sleep duration).
- Participants who slept fewer than 7 hours were 2.94 times more likely to develop a cold than those who had 8 hours or more sleep.
- The more efficiently a person slept (more of the time in bed actually spent asleep), the less likely he or she was to develop a cold (i.e. there was also a graded association between sleep efficiency and rate of infection).
- Participants whose sleep efficiency feel below 92 per cent were 5.50 times more likely to develop a cold than those whose efficiency was 98 per cent or more.
- Feeling rested was not linked to rate of infection.
Cohen and colleagues concluded that:
“Poorer sleep efficiency and shorter sleep duration in the weeks preceding exposure to a rhinovirus were associated with lower resistance to illness.”
The researchers also looked at separate components of illness and how they linked to the variables they measured.
“When the components of clinical illness (infection and signs or symptoms) were examined separately, sleep efficiency but not sleep duration was associated with signs and symptoms of illness,” they wrote, but “neither was associated with infection.”
“A possible explanation for this finding is that sleep disturbance influences the regulation of pro-inflammatory cytokines, histamines and other symptom mediators that are released in response to infection,” they suggested, recommending that seven to eight hours sleep a night would appear to be a reasonable target.
Additionally, the researchers said that previous studies had also shown that people who slept between seven and eight hours per night had the lowest rates of heart disease, illness and early death.
This study was supported by the National Heart, Lung and Blood Institute and by the National Institute of Allergy and Infectious Diseases. Supplementary funds were provided by the John D. and Catherine T. MacArthur Foundation with the Network on Socioeconomic Status and Health.
Study was published in Archives of Internal Medicine Vol. 169, No. 1, pp 62-67, January 12, 2009 by researchers, Sheldon Cohen; William J. Doyle; Cuneyt M. Alper; Denise Janicki-Deverts; Ronald B. Turner came to some stunning conclusions.
Sources: JAMA press release, journal abstract.
