Not enough sleep weakens the immune system and results in three times the likelihood of developing a cold, according to researchers at Carnegie Mellon University in Pittsburgh.
They have found that people who get less than seven hours of sleep a night are three times more likely to fall ill than those who sleep for eight hours or more.
Waking up in the night is also associated with colds. Test subjects who slept for less than 92% of the time spent in bed were five-and-a-half times more likely to suffer cold symptoms than those whose sleep efficiency was 98% or more.
The authors wrote in the journal Archives of Internal Medicine: "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."
Cytokines and histamines are both chemicals released by cells as part of the body's immune response.