No one likes nightmares, but having persistently bad dreams may also signal impending dementia, new British research suggests.
In the study, people aged 35 to 64 who had bad dreams weekly were four times more likely to have cognitive decline over the following 10 years, and older people were twice as likely to develop dementia, said Dr. Abidemi Otaiku. He is a clinical fellow in neurology at the University of Birmingham's Centre for Human Brain Health, in the United Kingdom.
"It is currently very difficult to determine who will develop dementia, especially during middle age. Therefore, discovering that nightmares in middle-aged and older adults might be linked to increased dementia risk could help contribute towards early identification," Otaiku said.
He cautioned, however, that this study can't prove that nightmares will lead to dementia, only that there appears to be an association.
Otaiku also found that the risk for dementia tied to nightmares was stronger among men than women. Older men who had weekly nightmares were five times more likely to develop dementia than men who had no bad dreams. Among women, however, the increase in risk was only 41%.
"Although the study does demonstrate that frequent bad dreams and nightmares in some adults may be linked to increased risk of dementia later in life, I do not think this should cause people with frequent nightmares to think that they are destined to get dementia," Otaiku said.
But if doctors were able to identify who is at most risk of developing dementia years or decades before memory and thinking problems arise, they would know who would most benefit from treatments to slow down or prevent thinking declines, he added.
Although some of these treatments are not yet available, scientists are actively working on developing them, he noted. "Given that nightmares are treatable with psychological therapies or medication, this raises the possibility that treating nightmares could also help to slow or prevent further cognitive decline," Otaiku said.
Using a 2002 to 2012 database from the United States, Otaiku collected information on more than 600 adult men and women between the ages of 35 and 64; and 2,600 adults aged 79 and older who didn't have dementia. The participants were followed for an average of five years for older participants and nine years for younger ones. Otaiku compared responses from questionnaires about sleep with a diagnosis of dementia.
It's not clear how nightmares might be connected to dementia, but Otaiku said that the same brain regions that help control emotions when you are awake also help control emotions when you dream.
"I suspect that some individuals who are in the earliest stages of dementia have subtle neuro-degeneration in parts of the brain that help to down-regulate negative emotions during wakefulness and dreaming," he said. "This may manifest in nightmares and depression in the years leading up to a dementia diagnosis."
The report was published online Sept. 21 in eClinical Medicine.
Sleep problems have already been linked with one type of dementia, said Dr. Sam Gandy, director of the Mount Sinai Center for Cognitive Health, in New York City.
"A range of sleep disorders is associated with dementia, especially Lewy body dementia," he said. "These sleep disorders include restless legs syndrome and visual hallucinations, as well as vivid dreaming and nightmares."
Lewy body dementia involves the build-up of a protein in the brainstem, which controls sleep, Gandy noted.
"These sleep disorders are so common in Lewy body dementia that, when present, they are considered to guarantee the diagnosis of Lewy body dementia," he said.
Although Lewy body dementia can co-exist with Alzheimer's disease, it's not always the case, and it is possible to have Lewy body dementia with sleep disorders without Alzheimer's disease, Gandy said. "Unfortunately, there is no medication available that tends to reduce the frequency or severity of Lewy body dementia or the sleep disorders associated with it," he added.
Maria Carrillo, chief science officer of the Alzheimer's Association, said, "Previous research has pointed to nightmares being indicative of potential changes in the brain that can precede other dementias like Parkinson's disease [dementia]. More research is needed to tease out what exactly is happening in the brain during nightmares that may be contributing to this increased risk."
Getting good sleep is important for overall health, including the health of the brain, she said.
"The good news is there are treatments that can help address sleep disturbances," Carillo added. "If you or a loved one is experiencing sleep difficulties, talk to your doctor."