Common opinion holds that getting a good night's sleep is a key to good health. Researchers at Stanford University are now much closer to turning that "opinion" into fact. In a study of the sleep pattern in fruit flies, scientists there have shown a link between the immune system and sleep.
The study, published in Current Biology (Volume 17, Issue 10, May 15, 2007), first examined the impact of illness on sleep. Flies were infected with one of two types of bacteria and then monitored. Subsequently, the sick flies slept less often and had shorter intervals of uninterrupted sleep compared to their healthy counterparts.
According to study's senior author, David Schneider, "When flies get sick, they stop sleeping. Disrupting sleep in turn disrupts the immune system, which makes them even more infected and it's downhill from there in a 'spiral of death.'"
Although the Stanford team is still unclear as to why the sleep behavior of the sick flies changed, their findings did establish that a weakened immune system affects sleep. They then sought to answer the inverse: Does sleep disruption cause illness?
To start to solve that question, scientists studied flies that had one of two genes -- known as Period and Timeless -- that were defective. These genes normally contribute to controlling circadian rhythm. (A circadian rhythm is an organism's internal clock that regulates a number of biological processes according to an approximate 24-hour period.) Compared to normally functioning flies, the mutant flies were more apt to get bacterial infections and lived significantly shorter lives.
How the internal clock and the immune system communicate is still unknown. But because flies and humans both share the two circadian clock genes studied, the researchers hope their findings will prompt other scientists to further investigate how molecular factors may influence sleep and immunity.
Other studies are also revealing how important a good night's sleep is to staying healthy. Consider the two studies below:
Study Ties Nighttime Breathing Problems to Depression
A poor night's sleep has always been cause for worry, particularly if it is due to difficulty breathing while asleep. Now, a recent study by Paul Peppard, Ph.D. and his colleagues at the University of Wisconsin-Madison suggests that individuals with sleep-related breathing disorder (sleep apnea) are also at a significantly higher risk of developing depression. (Signs of sleep-related breathing disorder include labored, interrupted or reduced breathing.)
Beginning in 1988, Peppard's team began evaluating over 1,400 adults between the ages of 30 and 60. Every four years, participants would spend a night at the University of Wisconsin-Madison's sleep lab, complete a questionnaire about their lifestyle habits, and report on their medical history. More than 3,200 sleep studies were conducted in all, and in 2005, the scientists concluded the study.
In the September 2006 issue of the Archives of Internal Medicine, the authors presented their results. After adjusting for other mitigating factors, they found that even individuals with mild sleep-related breathing disorder had much higher odds of becoming depressed than those without the disorder. As the condition worsened, so did the likelihood of depression. Those with moderate or worse sleep breathing problems were proven to be 2.6 times more likely to develop depression compared to those sleepers who breathed normally. Additionally, of the study's participants, women were almost twice as likely to be depressed as men.
Prior research has associated sleep-related breathing disorder with a number of health problems ranging from a lack of concentration to cardiovascular disease. With this new study's findings, it's hoped that doctors will be more aware of the threat of depression in patients with sleep-related breathing disorder as well.
Sleep Apnea: New Risk Factor for Stroke
Groundbreaking data out of Yale University find that people who suffer from sleep apnea are at twice the risk of stroke or death than those without the sleep-related breathing disorder. Severe sleep apnea triples the risk.
Obstructive sleep apnea, a condition where normal breathing is frequently interrupted as one's throat closes off throughout the night, affects up to 25% of all men and 10% of women. It is often characterized by loud snoring and consequent daytime sleepiness.
In a recent study, published in the New England Journal of Medicine (November 10, 2005), more than 1,000 men and women with no history of heart attack or stroke were tracked for an average of almost three and a half years. Participants were all over the age of 50 at the start of the study.
While sleep apnea has previously been linked to stroke and heart disease, the study's results are -- to date -- the most robust evidence to support that sleep apnea may cause stroke, rather than simply being associated with stroke.
As for the benefits of sleep apnea treatment, the Yale study was not designed to answer this question, as they had no method to monitor who was or was not using a continuous positive airway pressure (CPAP) machine. CPAP machines are commonly used to alleviate sleep apnea by keeping the throat open at night, allowing users to sleep better.
While treatment is effective for reducing snoring, daytime drowsiness, and high blood pressure, the study's lead researcher, Dr. H. Klar Yaggi, noted that further research is really necessary to gauge how treating apnea affects the risk factor for stroke.
