People who sleep fewer than six hours a night or more than nine are more likely to be obese, according to a new government study that is one of the largest to show a link between irregular sleep and big bellies. The study also linked light sleepers to higher smoking rates, less physical activity and more alcohol use.
The research adds weight to a stream of studies that have found obesity and other health problems in those who don't get proper shut-eye, said Dr. Ron Kramer, a
The study released Wednesday is based on door-to-door surveys of 87,000
Such surveys can't prove cause-effect relationships, so for example it's not clear if smoking causes sleeplessness or if sleeplessness prompts smoking, said Charlotte Schoenborn, the study's lead author.
It also did not account for the influence of other factors, such as depression, which can contribute to heavy eating, smoking, sleeplessness and other problems.
Smoking was highest for people who got under six hours of sleep, with 31% saying they were current smokers. Those who got nine or more hours also were big puffers, with 26% smoking.
Results were similar, though a bit less dramatic, for obesity: About 33% of those who slept less than six hours were obese, and 26% for those who got nine or more. Normal sleepers were the thinnest group, with obesity at 22%.
For alcohol use, those who slept the least were the biggest drinkers. However, alcohol use for those who slept seven to eight hours and those who slept nine hours or more was similar.
In another measure, nearly half of those who slept nine hours or more each night were physically inactive in their leisure time, which was worse even than the lightest sleepers and the proper sleepers. Many of those who sleep nine hours or more may have serious health problems that make exercise difficult.
Many elderly people are in the group who get the least sleep, which would help explain why physical activity rates are low. Those skimpy sleepers who are younger may still feel too tired to exercise, experts said.
Stress or psychological problems may explain what's going on with some of the lighter sleepers, experts said.
Other studies have found inadequate sleep is tied to appetite-influencing hormone imbalances and a higher incidence of diabetes and high blood pressure, noted James Gangwisch, a respected