Short Sleep Affects Personality

Short sleep—sometimes defined as sleeping less than 6 hours a night, and other times defined as sleeping less than 5—is associated with a higher risk of hypertension, obesity, and type 2 diabetes, investigators at Penn State Hershey have said. Some research has even shown there’s a link between short sleep and increased mortality.

Now a new study finds that short sleep also has effects on personality.

short-sleepShort sleepers get short-changed in more ways than one. Short sleep—sometimes defined as sleeping less than 6 hours a night, and other times defined as sleeping less than 5—is also associated with a higher risk of hypertension, obesity and type 2 diabetes, investigators at Penn State Hershey have said. Some research has even shown there’s a link between short sleep and increased mortality.

A new study published in the International Journal of Behavioral Medicine finds that short sleep also has effects on personality. European investigators Sakari Lemola and colleagues, after evaluating medical data on about 1,800 Americans aged 30 to 84, concluded that people who sleep less than 6 hours a night are less optimistic than people who sleep 7 to 8 hours a night, and that short sleepers have lower self-esteem.

Pessimism and low self-esteem are also characteristic of depression. But even when the researchers controlled for symptoms of depression, the relationship between short sleep and decreased optimism and self-esteem held up.

The Upshot

This study supports a growing awareness that the amount of sleep people get can affect their sense of well-being. And it adds to the body of research suggesting that short sleep is linked to poorer health. “Longitudinal studies indicate that optimism and self-esteem are predictors of better health rather than just consequences,” the authors write.

One limitation of the current study is that, unlike the protocol followed at Penn State Hershey, short sleep was assessed subjectively rather than being objectively validated in a sleep lab. And a major caveat in all the short-sleep studies is that none of them allow for assumptions about causality. Whether short sleep actually leads to lower optimism, lower self-esteem and poorer health or vice versa is not known.

Still, it gets harder and harder for anyone to say that people who consistently experience short nights should just buck up and bear them. If there’s any silver lining to the cloud, this is it.

Awake in the Middle of the Night

The bed—so sleep experts maintain—should only be used for sleep and sex. People who can’t sleep should get up and do something: iron shirts, look at picture books, plan a backyard stupa. Anything, for God’s sake, but toss and turn among the sheets.

I know I should follow this advice. But every fiber of my body cries out for staying flat on my back.

The bed—so sleep experts maintain—should only be used for sleep and sex. People who can’t sleep should get up and do something: iron shirts, look at picture books, plan a backyard stupa. Anything, for God’s sake, but toss and turn among the sheets.

This bit of advice has always put me off. Especially when I wake up in the middle of the night and can’t fall back to sleep, I’m bone-tired and brain-dead. I can barely face getting out from under the warmth of the covers to go to the bathroom, let alone contemplate walking downstairs, turning on a light and settling down with a book. Every fiber of my body cries out for staying flat on my back.

Making Hay While the Darkness Reigns

But I’ve met insomnia sufferers of the middle-of-the-night-awakening type who decided at some point that they were not going to take their wakefulness lying down.

My former colleague Claudia is a journalist with a greeting card business on the side. She used to lie awake fretting when she couldn’t fall back to sleep. Now when she wakes up at 1 a.m., she goes upstairs to make birthday cards.

“It’s like playing around,” she says. “It takes my mind off everything, and sometimes I think it helps me mellow out a little, too.” After working a couple of hours on her cards – an activity she says is fun but not cerebral – she crawls back into bed again and can usually get a few more hours of shut-eye. She’d rather deal with insomnia this way than take sleeping pills.

Marty is another example. Self-employed, he goes to bed around 9 p.m. and uses the time he’s awake in the middle of the night to work on an online newsletter. “I do my best writing between 2 and 5 in the morning, “ Marty says. Then he goes back to sleep for another hour and a half. He’d like to sleep more, and to get all his sleep at one go, but his body seems to have different needs.

Bimodal Sleep in Nights Past

Historian A. Roger Ekirch claims this pattern of broken sleep was actually common before 1800, when people lived without artificial lighting in their homes. Ekirch has found several references to nights in which people took their “first” sleep from about 9 or 10 p.m. to somewhere past midnight. Then they got up to brew a tub of ale or chat with neighbors, or they stayed in bed to pray, make love or meditate on dreams. At last they fell into a “second” or “morning” sleep that lasted until dawn.

Experiments conducted by sleep researcher Thomas Wehr in the 1990s suggest this bimodal pattern of sleep is the pattern humans might well fall into today in the absence of artificial lighting. Our modern lights-out period lasts for seven or eight hours a day year-round. But in temperate climates in the pre-industrial era, during the winter months when darkness lasted 14 hours, people spent a lot more time in rest and relaxation.

When Wehr re-created these conditions by giving his experimental subjects a 14-hour sleep window, they settled into a routine in which their sleep fell into two distinct periods. One came at the beginning of the “biological” night and one at the end, with a period or periods of quiet wakefulness in between. Wehr concluded that bimodal sleep may actually be more “natural” than the consolidated sleep period that is the norm today.

The notion may not be reassuring to insomniacs unable to turn middle-of-the-night awakenings to their advantage, or whose work or families demand that they be up at the crack of dawn. Nor does it jibe with the thinking of most sleep experts, who suggest that a consolidated period of sleep is for the insomniac the Holy Grail. But if segmented sleep really does come more naturally to some poor sleepers, then the Claudias and Martys may be better off going with the flow.