This article originally appeared on RealSimple.com.
Older adults who begin sleeping more than nine hours a night might want to talk to their doctors about their increased need for shuteye: A new study suggests that it may be an early sign of dementia.
But that’s not to say that every parent or grandparent who starts snoozing extra will definitely develop memory problems. There are a lot of other conditions that can affect sleepiness and time spent in bed, says study co-author Matthew Pase, PhD, a neurology fellow at the Boston University School of Medicine, some of which are treatable once diagnosed.
Pase’s new study looked at 2,457 people, average age 72, who had health assessments and responded to health questionnaires every few years. Of those participants, the researchers identified 75 people who reported sleeping more than nine hours a night on average when they used to sleep less.
Those long sleepers were more than twice as likely to be diagnosed with dementia over the next 10 years than other study participants. (Adults who had always reported sleeping nine hours or more did not have an increased risk of dementia—only those whose sleeping habits had changed as they got older.)
A doubling of risk may sound like a big increase, but Pase points out that the absolute risk is not as alarming: Only 21 percent of the extended-sleep participants, and 9 percent of other participants, actually got dementia. “By no means is this a certain fate for these people,” he says.
The study included all forms of dementia, including Alzheimer’s disease, the most common type. The researchers don’t believe that sleeping longer hours actually has any effect on the progression of memory loss and cognitive decline; rather, they think it’s a subtle sign that early brain changes have started to occur. “In other words, restricting sleep is not likely to be effective,” Pase says.
More research is needed to know exactly why the body might react this way, but one theory is that the brain tries to compensate for early dementia-related changes by spending more time in sleep, Pase says, where it can try to repair itself.
The study made another interesting finding, as well: The chances of dementia were highest—about six times greater than those who slept less than nine hours a night—for people without a high-school degree who had recently started sleeping more. This supports the idea that having more education may be protective against dementia later in life, the authors wrote.
If you notice an elderly friend or relative begins sleeping more, that in itself is probably not cause for alarm, says Pase, since this can be a normal part of aging or may be influenced by lots of other things. But whatever its root cause, it’s probably worth mentioning to a doctor—especially if your loved one is also having memory or thinking problems on top of longer sleep.