Is she just more disciplined than you are? Did she train herself to “need” less sleep? Is she just saying that to make you feel like a slug? While you may too tired to decide, a study published this week in the journal Neurology supplies the likely answer: It’s in her genes" href="http://history.nih.gov/exhibits/genetics/sect1a.htm" target="_blank">genes. And your exhaustion is in yours, as well.
The Neurology study, conducted at University of Pennsylvania School of Medicine, found evidence that “interindividual differences” in the way we fall asleep, stay asleep and cope with sleep shortage can be predicted reliably by whether or not we have inherited an allele called DBQ1*0602.
You may very well be one of the more than one-in-four people who are positive for the DBQ1*0602 allele, which happens to be a genetic marker for NIH narcolepsy page" href="http://www.ninds.nih.gov/disorders/narcolepsy/narcolepsy.htm" target="_blank">narcolepsy--a sleep disorder that causes sufferers to fall deeply asleep during the day with little warning. Most narcoleptics have this genetic peculiarity, although being DBQ1*0602-positive is no assurance you’ll be narcoleptic. Compared to those without this allele, someone who’s positive for this allele is likely to fall fitfully into sleep even when she’s exhausted; break free from sleep’s hold several times a night, and feel miserably sleepy when he hasn’t gotten enough shut-eye.
That resilient co-worker, by contrast, appears to be in the genetic majority: DBQ1*0602-negative. Faced with the prospect of less sleep, her body and brain settle into sleep more quickly, slide seamlessly into deep sleep, and stay under until she has to wake up.
After putting 129 healthy adults through a five-night ordeal of sleep deprivation and its effects" href="http://www.nhlbi.nih.gov/health/prof/sleep/res_plan/section2/section2.html" target="_blank">partial sleep deprivation (four hours per night), the authors of the Neurology study found no actual differences in cognitive performance between those who were positive and those who were negative for the allele: the differences were in how sleepy and fatigued individuals in the two groups felt after five nights of abbreviated sleep.
In a world where sleep is in CDC Report on chronic sleep shortage" href="http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5842a2.htm" target="_blank">chronically short supply, this kind of research is of considerable interest to employers. In lines of work where hours can be long, sleep is had in short bursts, and alertness is non-negotiable—e.g. fighting wars, tending to the sick, driving trucks and flying commercial aircraft—finding people who can function well on little sleep is essential. As research refines how our genes influence our sleeping patterns, some ethicists worry research like this will be used to weed out those who genes predispose them to tolerate sleep deprivation poorly. (The Genetic Information Nondiscrimination Act—GINA—made law in 2008 makes such actions illegal. But that legal protection can genetics in a post-GINA world" href="http://www.cell.com/AJHG/retrieve/pii/S0002929708004904" target="_blank">potentially be short-circuited by arguments about public safety or national security.)
Namni Goel, the author of the Neurology study published this week, says that using such research to weed out employees who feel miserable when sleep deprived “would be a negative outcome.” She’d rather people use such information to help themselves function optimally: if they know they’re genetically vulnerable to sleep deprivation, they should have a cup of coffee or take a nap when they’ve failed get enough nighttime sleep, said Goel.