The relationship between sleep and dementia is an active area of research with previous studies linking lower sleep quality to an increased risk of the condition. Sleep occurs in cycles which last around 90 minutes and involve five stages, each with particular characteristic features. REM (rapid eye movement) sleep is the final stage of a sleep cycle and the point at which we are most likely to dream. Researchers in this study investigated whether individual differences in the timing of these stages was linked to the risk of dementia.
The researchers worked with members of the Framingham Heart Study, a large population study that has been following a group of people and their children since 1948, producing a wealth of information about heart disease and other conditions. This study involved assessing the sleep patterns of 321 members of the Framingham Heart Study, all of whom were over 60 years of age and did not have prevalent dementia at the time of the sleep assessment. The participants completed regular memory and thinking tests and over 12 years follow up, 32 people in the study developed dementia, 24 of whom were diagnosed with Alzheimer’s disease.
People who went on to develop dementia spent an average of 17% of their sleep time in REM sleep compared to 20% for people who didn’t go on to develop dementia. They also found people who developed dementia tended to have longer intervals between periods of REM sleep, with an average of 87 minutes compared to 70 minutes for people who didn’t develop dementia. The study also found that differences in non-REM sleep were not associated with the risk of developing dementia.
Dr Alison Evans, of Alzheimer’s Research UK, said:
“Sleep disturbance is a common symptom for people living with Alzheimer’s disease and a number of other forms of dementia. This small study adds to evidence of sleep changes preceding the onset of memory and thinking changes, and suggests that levels of REM sleep may be particularly relevant to the risk of future dementia symptoms.
“We know that brain changes in diseases like Alzheimer’s can begin in the brain over a decade before symptoms start to show, and it is impossible to tell from this study whether disturbed REM sleep could be causing increased dementia risk or whether it’s an early consequence of disease processes already underway in the brain. It is also possible that REM sleep may be disturbed as a result of stress, a factor that has previously been linked to an increased risk of dementia.
“Larger studies involving more detailed testing will be necessary to better understand the complex relationship between sleep and dementia, and help us to understand why people who go on to develop dementia tend to have less REM sleep. Getting to the bottom of these questions could present new avenues by which to diagnose, prevent or treat dementia, and the only way that this will happen is through continued investment in research.”