Posted on 21 September 2022
Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.
Why is this research important: About 5% of adults experience nightmares at least once a week. These can be caused by stress, anxiety, and sleep deprivation, but research also suggests that these dreams are associated with accelerated cognitive decline in people with Parkinson’s disease. Does a similar relationship exist in healthy people?
What did the researchers do: In this study, researchers looked at data from three previous studies that followed a total of 605 middle-aged and elderly adults. Participants had normal cognitive function (as assessed by 5 different cognitive tests) at the start of the study, and were followed-up for up to 13 years. Participants reported the frequency at which they experienced distressing dreams, and researchers investigated whether this frequency was associated with faster cognitive decline and greater incidence of dementia during the follow-up period.
Key takeaway(s) from this research: Compared to participants who reported having no distressing dreams at the start of the study, those who reported weekly distressing dreams were four times more likely to experience cognitive decline. Among the elderly participants, those experiencing frequent distressing dreams were just over twice as likely to develop dementia during the follow-up period. However, these relationships were far stronger for male participants, and were not statistically significant for female participants.
There are a few possible explanations for this relationship. People who have more frequent nightmares don’t sleep as well, and evidence suggests that this contributes to cognitive decline. It’s also possible that other factors such as stress are the cause of both the nightmares and the cognitive decline, though researchers attempted to control for such confounders. However, the authors suggest there’s also a possibility that more frequent nightmares are a consequence of neurological changes that precede dementia. Neurodegeneration within the frontal lobe could lead to nightmares, providing an early sign of neurodegenerative disease (though researchers stress that only a subset of adults with bad dreams will develop dementia).
As for the difference between men and women, this could be related to the the fact that women tend to experience more nightmares in youth and fewer nightmares as they age, while for men the reverse is true.
Distressing dreams, cognitive decline, and risk of dementia: A prospective study of three population-based cohorts: https://doi.org/10.1016/j.eclinm.2022.101640