In the last decade, science has made enormous strides in decoding the human genome and finding associations between genetic variants and certain conditions, or diseases and disorders. We owe a lot of our individual characteristics, after all, to minor variations in our DNA. So it seems reasonable that small discrepancies in our genomes can mean the difference between being a routinely sound sleeper and a chronic insomniac.
And now we have proof: new research just published in the journal Neurology concludes that people who have a gene variant called DQB1*0602 have a higher chance of developing narcolepsy. It’s not that having this variant dooms a person to narcolepsy, a sleep disorder that causes excessive daytime sleepiness. The association is probabilistic—not deterministic, meaning if you might develop narcolepsy if you have the gene, or you might not. Depending on the population, 12 to 38 percent of those with the variant do not have the sleep disorder and are considered healthy sleepers. Also, people without the gene variant can develop narcolepsy, though this is less common.
Here’s how the study was performed in a sleep lab:
- Ninety-two healthy adults without the gene variant were compared to 37 healthy adults who had the gene variant but did not have any sleep disorders.
- For the first two nights, they spent 10 hours in bed and were fully rested. The next five nights they underwent chronic partial sleep deprivation, also known as sleep restriction, where they were allowed four hours in bed per night.
- During the remaining time, 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 results clearly pointed to the effects the DQB1*0602 gene variant can have on people, as those with the gene variant were sleepier and more fatigued when 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 twice. Those with the gene variant also had a lower sleep drive, or desire to sleep, during the fully rested nights.
The participants with the gene variant also spent less time in deep sleep than those without the variant during both nights. During the second fully rested night, those with the variant averaged only 34 minutes in stage three sleep, while those without it averaged 43 minutes. That may not seem like a big difference, but every minute counts in sleep.
The two groups performed the same on the tests of memory and attention.
I predict that we’ll find future associations between genes and sleep disorders, which can help us to understand why someone can get away with just 4 hours a night while others require nine hours. Such findings can also help us predict who will be more negatively impacted by challenges to a restful night’s sleep, such a shift work or restless leg syndrome.
It’s important to note that having gene variants isn’t necessarily a “bad” thing; there are lots of variants that give you the edge—the advantage over others. This is true for all kinds of areas in life. Genetic variants help explain why some people can live at very high altitudes and summit Mt. Everest without oxygen.
It’s an exciting time in medicine. Though we can’t change our genes, we can influence how those genes express themselves by addressing our environments. Studies like this latest one doesn’t mean we can throw sleep hygiene out the window. Much to the contrary, it reinforces the need to optimize our sleep hygiene to maximize our sleep quality no matter what kind of genes are dictating our life from deep within.
(For more information about narcolepsy, visit The Narcolepsy Network.)
Michael J. Breus, PhD
The Sleep Doctor™