Of all the useless advice I’ve ever had for —and there’s been plenty— the most irksome is this: you’re probably getting all the sleep you need, don’t worry about it—just buck up and get a grip, change your attitude, you’ll be fine. Actually, I’m pretty clear about how much sleep I need; when I feel sleepstarved, I really am.
When you start asking people about their sleep—as I did, writing INSOMNIAC—you find that they vary enormously in terms of how much sleep they need and how they weather sleep loss, and there’s not a lot they can do about it.
A new study at U.C. San Francisco suggests that whether we need a lot or little sleep is not about whether we have a positive or negative attitude — but whether we have the DEC2 mutation.
Dr. Ying-Hui Fu and her colleagues looked at a family in which the mother and daughter require significantly less sleep than other family members, 6 hours to their 8. They found that the DEC2 gene was mutated in the short sleepers. They then genetically modified mice to carry the same mutation, and sure enough, the mutated mice slept on average two and a half hours less than the normal mice— with no noticeable differences in health or performance. (Science, August 14)
Another study, lead by Pierre Maquet at the University of Liege in Belgium and Derk-Jan Dijk at the University of Surrey, suggests that whether we’re clobbered by sleep loss or remain perky and functional is about whether we carry the short or long variant of the PER3 gene. People with the short variant perform better on cognitive tasks after sleep deprivation than those with the long PER3 variant. Brain imaging showed their brains were more active after the sleep deprived night, and this seemed to be correlated with better performance. (Journal of Neuroscience, June 24)
It’s no surprise. So many sleep behaviors turn out to be genetically programmed. Scientists have long known that identical twins, even when not raised together, have sleep patterns more similar to one another than do non-identical twins or other sibling pairs, in terms of bedtime, length of sleep, length of time it takes to get to sleep, and even quality of sleep. Scientists now know which genes are associated with morningness and eveningness.
So when we insomniacs complain about being clobbered by sleep deprivation, please don’t tell us we’re getting all the sleep we need and if we changed our attitude we’d be fine. And if you’re one of those fortunate people who does well on little sleep—and there are probably lots of doctors who are— don’t be so hasty to judge the sleep needs of others by your own needs. We’re all very different when it comes to sleep and sleep need, and these differences are no more to anyone’s credit or discredit than blue eyes or blond hair.