Why are some people often sick while others rarely are?
The amount and quality of sleep may be important predictors of susceptibility to respiratory infections. A frequently cited study published in Archives of Internal Medicine in 2009 examined the relationship between sleep and susceptibility to the common cold.
Researchers studied 153 healthy men and women aged 21 to 55. For 14 consecutive days, participants reported their sleep duration and sleep efficiency—the percentage of time in bed that they were actually asleep. The researchers then calculated average sleep measures for each participant.
The participants were subsequently quarantined and given nasal drops containing a rhinovirus, one of the viruses that can cause the common cold. Researchers then monitored them for the development of a clinical cold.
What did the researchers find?
Shorter sleep duration and poorer sleep efficiency in the weeks before exposure were associated with greater susceptibility to the cold. Participants who slept fewer than seven hours were almost three times as likely to develop a cold as those who slept eight hours or more.
Sleep quality also appeared to matter. Participants with sleep efficiency below 92% were reported to be about 5.5 times as likely to develop a cold as those with sleep efficiency of 98% or higher.
What this means: this study shows an association and does not mean that sleep alone determines whether someone becomes ill. Immunity is influenced by many factors, including age, vaccination, underlying health, stress, nutrition and exposure to pathogens. Nevertheless, adequate, consistent sleep is an important part of supporting normal immune function.
Study: Cohen S, Doyle WJ, Alper CM, Janicki-Deverts D, Turner RB. Sleep habits and susceptibility to the common cold. Arch Intern Med. 2009;169(1):62–67.