HELSINKI — Nightmares in middle age are linked to a significantly increased risk for subsequent dementia, new research suggested. However, one expert is skeptical that this is the case.
Investigators found that middle-aged adults who reported having weekly distressing dreams at baseline had a fourfold increased risk of developing dementia compared with their counterparts who had no nightmares.
"It is likely that distressing dreams are either a causal risk factor for dementia or one of the earliest signs of it," said study investigator Abidemi Otaiku, MD, Imperial College London, London, England.
The findings were presented here at the Congress of the European Academy of Neurology (EAN) 2024 annual meeting.
Robust Link
As previously reported by Medscape Medical News, Otaiku and colleagues found healthy middle-aged adults from the MIDUS study who had bad dreams at least once a week were four times more likely to experience cognitive decline over the following decade than those without distressing dreams. In addition, older adults who reported nightmares had a twofold increased risk for all-cause dementia.
The current study furthers the previous research by analyzing a subset of study participants who had genetic data available that was based on blood tests, saliva samples, and family history to determine if these had any impact on the previous findings.
"We found that after controlling for genetic factors, the association between distressing dreams and both cognitive decline and dementia remained robust," Otaiku told Medscape Medical News. "We also found that there was no significant relationship between distressing dream frequency and genetic factors in either age group."
Given that there's no cure for Alzheimer's disease (AD) or other dementia types, "it's important that we identify people at the early stage before they develop symptoms, so they can benefit from disease-modifying drugs, when available, and preventive strategies," Otaiku added.
Future studies are needed to determine whether treating distressing dreams could help slow cognitive decline and/or prevent dementia, he said.
In response to a question from the audience about rapid eye movement (REM) sleep behavior disorder following his talk, Otaiku said he did not have data on this but added that he believes it's unlikely that it explains the association between bad dreams and dementia.
He pointed out that REM sleep behavior disorder is very rare, affecting < 0.05% of the population of those aged 50 years and older. Second, he said there has been one study, to his knowledge, looking at REM sleep behavior disorder and all-cause dementia, which showed the disorder did not predict all-cause dementia, whereas nightmares were predictive.
Finally, said Otaiku, there are data on diagnosed sleep disorders from one of his studies, which showed that even when all participants with a diagnosed sleep disorder were excluded, the relationship between nightmares and dementia risk remained robust.
"Therefore, it seems unlikely that REM sleep behavior disorder explained the association," he said.
Otaiku noted his team also adjusted for neuropsychiatric disorders such as anxiety, depression, and stress, and still the link between nightmares and dementia risk remained robust. Similarly, they adjusted for medication use, including antidepressants, benzodiazepines, and hypnotics, and found this also didn't explain the increased dementia risk.
He noted that the study had an outcome of all-cause dementia and that his team didn't have access to data on specific dementia diagnoses.
"Presumably, Lewy body dementia would be one of the strongest associations, but given that this makes up less than 5% of diagnoses in the community, it's likely that the effects may apply to Alzheimer's disease too, and previous studies have shown that nightmares are more common in Alzheimer's disease at certain stages," he concluded.
A More Likely Culprit?
Commenting on the research for Medscape Medical News, Sebastiaan Engelborghs, MD, PhD, professor and chair of neurology, Vrije Universiteit Brussel, Brussels, Belgium, and co-chair of the EAN Scientific Panel on Dementia and Cognitive Disorders, said the findings are not novel.
"I suspect the subjects with 'distressing dreams' to have rapid eye movement (REM) sleep behavior disorder. This can only be ruled out by a sleep exam, which was not performed — to my knowledge — in this study."
"It is well-known that REM sleep behavior disorder may precede dementia by many years. One of the key symptoms of REM sleep behavior disorder are nightmares, or 'distressing dreams'…and this is why we always ask about sleep and nightmares during consultations in the memory clinic," Engelborghs added.
"That is also why we follow up on cognitively healthy subjects who show up with nightmares, suggestive of REM sleep behavior disorder, as we do know that they are at increased risk of developing dementia, and we disclose this to them," he added.
Speaking to Otaiku's suggestion that future trials could assess whether treating distressing dreams might slow the onset of, or prevent, dementia, Engelborghs said that his patients with REM sleep behavior disorder are treated with specific medications "as the symptoms can be very distressing."
However, he noted treating sleep symptoms does not reduce dementia risk. Disordered sleep is often the first, early manifestation of neurodegeneration that is the cause of future dementia, he said.
Note: This article originally appeared on Medscape.
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