Researchers at Carnegie Mellon University in Pittsburgh, US came to the conclusion that people who sleep less than seven hours per night have a three times higher risk of catching a cold than those who shut-eye for eight hours or more. Getting a good night's sleep might not cure the common cold, but the new study says that it could prevent one. According to scientists, sleep is very closely connected to the strength of the immune system and that is why people feel tired and exhausted when they have an infection or are sick. The conclusions were based on an analysis of 153 healthy people with an average age of 37 between 2000 and 2004. Also, a wide variety of factors was taken into consideration, such as age, weight, socioeconomic status, stress, smoking, and alcohol consumption.
Volunteer participants were interviewed on a daily basis for two weeks, reporting how many hours of sleep they got per night, how well they slept and how rested they felt, their sleep habits being documented and then quarantined in a hotel for 24 hours (with instructions to stay at least several feet away from other people to limit spread of the infection), where the common-cold-causing rhinoviruses (the most common viruses that cause colds) were dropped into their noses. For five days the study participants were monitored for sneezing, coughing, stuffy noses, and had mucus samples collected from their nasal passages. After about a month, they submitted blood samples that were tested for immune system proteins (antibodies) responding to the virus. As a result, participants who slept less than seven hours were four times more likely to get sick than participants who slept for eight hours or more. Among the 153 study volunteers, 135 were infected, but only 54 developed a cold. People who had the best sleep efficiency (defined as the percentage of time actually spent in sleep) were the least likely to get ill. 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 chemicals that are being released by cells as part of the body's immune response. "Although sleep's relationship with the immune system is well-documented, this is the first evidence that even relatively minor sleep disturbances can influence the body's reaction to cold viruses," Sheldon Cohen, a psychology professor at Carnegie Mellon University, who led the study said in his statement.
So what is more important: number of sleep hours or sleep quality? Cohen suggests that both are very essential, that someone who sleeps more efficiently is also likely to sleep for longer hours. The experts believe that lack of good quality sleep prevents regulation of key chemicals produced by the immune system to fight infection and say that sleep and the immune system are were closely linked. "The immune system may control the sleep-wake pattern and lack of sleep or sleep disturbance may depress the immune response to infection," Ron Eccles, Professor and director of the Common Cold Centre at the University of Cardiff says, "I do believe there is enough information on this to indicate that lack of sleep or sleep disturbance will reduce our resistance to infections such as colds and flu."
The connection between sleep patterns and bad health has also been examined in the previous research of coronary heart disease, which discovered that the lowest death rates and less illness were found in people who slept at least seven-eight hours per night. Previous research has shown that lack of sleep may result in the immune system changes that could make a person more vulnerable to infections but there was little data on its effect on specific infections, such as colds and flu. The current study is one of the first studies that links sleep problems to increased susceptibility to the rhinovirus, the most common cold. It has become pretty clear that long and uninterrupted sleep has major effects not only on the brain in terms of alertness and performance, but also on the health of the body. "Getting good sleep should count among the priorities of health-conscious people," says David L. Katz, director of the Yale University School of Medicine Prevention Research Center, "Time invested in sleep will almost certainly be paid back in dividends of better health - fewer colds and greater productivity." So, there is another reason now why people should take more seriously the problem of sleepless nights and make time in their schedules to get a complete night of rest.
The study was published in Monday's edition of the medical journal Archives of Internal Medicine.
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