Research 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% of those with the variant do not have the sleep disorder and are considered healthy sleepers.
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.