A new study has found that middle-aged adults who suffer from frequent nightmares may be more likely to develop dementia later in life.

The study, published in The Lancet Journal on Wednesday, indicates that people diagnosed with dementia in their later years show cognitive decline years in advance, with signs such as disturbing dreams.

Researchers at the University of Birmingham in the UK analyzed data from three separate cohort studies in the United States that followed 605 men and women aged between 35 and 64, and 2600 adults aged 79 or older. The data tracked all participants for an average of nine years, all of whom were dementia-free at the start of the study.

Participants were asked to complete the Pittsburgh Sleep Quality Index questionnaire, which assesses a person's sleep patterns and quality. The questionnaire covers a variety of sleep factors including sleep duration, use of sleeping medications, daytime dysfunction, and sleep disorders.

From the collected data, researchers found that middle-aged participants who suffered from weekly nightmares were four times more likely to experience cognitive decline over the next decade compared to those who did not have nightmares. Among those aged 79 or older, participants who experienced weekly bad dreams were more likely to develop dementia. Lead researcher Dr. Abidemi Otaiku said in a press release: "This is important because there are very few risk indicators for dementia that can be identified as early as midlife."

According to the Alzheimer Society of Canada, sleep disorders are very common among people with dementia, as their sleep problems can range from insomnia, frequent napping throughout the day, sleeping all day, and staying awake all night. This often leads to "sundowning," which is when a person with dementia experiences severe confusion or aggression late in the afternoon or early evening.

The study's authors hypothesize that the relationship between nightmares and cognitive decline may be linked to neurodegeneration. This gradual damage to nerve cells, specifically in this case, attacks the right frontal part of the brain, which is supposed to suppress negative emotions during conscious states such as dreaming. The researchers also assumed this because most participants who experienced nightmares were more likely to be depressed or anxious. The researchers say they aim to further investigate other factors related to dreaming patterns that may be linked to dementia, including the frequency of dreams or how vivid the dreams may be.

In the same context, Otaiku said in his article: "While more work is needed to confirm these links, we believe that bad dreams could be a useful way to identify individuals at high risk for dementia and to develop strategies to slow the onset of the disease."