Women, try not to think of this if you lie awake at night: having trouble sleeping means you're likely to gain weight.
As if simply getting older weren't hard enough, new research shows that middle-aged and older women who have trouble falling or staying asleep may pack on more pounds than their well-rested contemporaries.
A number of studies have found that sleep-deprived children and adults are more likely to be overweight than those who usually get a full night's rest. But many of those studies assessed people at one point in time, so it was hard to know which came first, the sleep problems or the excess pounds.
A few studies have followed people over time, but they've disagreed about whether poor sleep is linked to expanding waistlines.
The new findings, reported in the International Journal of Obesity, strengthen the evidence that sleep problems are related to weight gain. In this case, the study design allowed the researchers to show that sleep problems came before substantial weight gain in some participants.
Finnish researchers followed more than 7,300 40- to 60-year-old adults for seven years. They found that women who reported significant sleep problems at the outset generally put on more weight over time than women who slept well.
Roughly one-third of women with frequent sleep problems gained at least 11 pounds, versus about a fifth of women with no sleep difficulties at the outset.
Men were spared, however. Their sleep problems were not related to weight gain.
The link in the women persisted even when the investigators accounted for a number of factors that can affect both sleep quality and weight gain -- including participants' body weight at the study's start, their exercise habits and their general physical and mental health.
While the findings do not prove cause-and-effect, they raise the possibility that improving sleep quality might help stave off excess weight gain, lead researcher Peppi Lyytikainen, of the University of Helsinki, told Reuters Health by e-mail.