October 26, 2010

Sleep Affects You … Because Your Genes Say So?

(Ivanhoe Newswire) -- Have you ever wondered how some people go about their busy days on only 4 hours of sleep while others need at least 8 to function? This study suggests that genes may play a role in how the amount of sleep we get affects us.

The study examined people who have a gene variant that is closely associated with narcolepsy, a sleep disorder that causes excessive daytime sleepiness. Having the gene variant, called DQB1*0602, doesn't mean that a person will develop narcolepsy. About 12 to 38 percent of those with the variant don't have narcolepsy and are considered to be healthy sleepers. Also, people without the gene variant can develop narcolepsy, but it is much less common.

The study evaluated 92 healthy adults without the gene variant and 37 adults with the gene variant, but without narcolepsy. All of the participants came to a sleep laboratory. For the first two nights, they spent 10 hours in bed and were fully rested. The next five nights, were spent in chronic partial sleep deprivation where they were allowed four hours in bed per night. During the remaining hours, lights were kept on and participants could read, play games, or watch movies to help them stay awake.

Researchers measured their sleep quality and self-rated sleepiness and tested their memory, attention and ability to resist sleep during the daytime.

The researchers found that people with DQB1*0602 gene variant were sleepier and more fatigued while they were both fully rested and sleep deprived. Their sleep was more fragmented. For example, those with the gene variant woke up, on average, almost four times during the fifth night of sleep deprivation, compared to those without the gene variant who woke up on average only twice. Those with the gene variant also had a low desire to sleep during the fully rested nights.

The people with the gene variant also spent less time in deep sleep than those without the variant, during both the fully rested and sleep deprived nights. During the second full rested night, those with the variant had an average of 34 minutes in deep, stage three sleep, compared to 43 minutes for those without the variant. During the fifth night of sleep deprivation, those with the variant spent an average of 29 minutes in stage three sleep, compared to 35 minutes for those without the gene variant.

The two groups scored equally on tests of memory and attention, and there was no difference in ability to stay awake during the daytime.

"This gene may be a biomarker for predicting how people will respond to sleep deprivation, which has significant health consequences and affects millions of people around the world. It may be particularly important to those who work on the night shift, travel frequently across multiple time zones, or just lose sleep due to their multiple work and family obligations.

However, more research and replication of our findings are needed," lead study author Namni Goel, PhD, of the University of Pennsylvania School of Medicine in Philadelphia was quoted as saying.

SOURCE: Neurology, published online October 25, 2010