Short 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.
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.