Does talking in your sleep tell us anything about dementia?

Ordinary sleeptalking on its own is not a sign of dementia. But a specific form of it, namely sleeptalking as part of REM sleep behaviour disorder, tells a very different story. In that disorder, you actively act out your dreams: you kick, hit or talk loudly during the REM phase of your sleep. That pattern is strongly linked to brain diseases in which a particular protein (alpha-synuclein) accumulates in the brain, such as Lewy body dementia and Parkinson's disease.

Of the people who have such a REM sleep behaviour disorder without a diagnosis having been made yet, more than 80% eventually develop one of those brain diseases. That happens at an average rate of just over 6% per year. After twelve years of follow-up, more than 73% of participants had been diagnosed with such a disease. This emerges from a large international study involving more than 1,200 participants.

Sleeptalking can also help to distinguish between types of dementia. Loud sleeptalking occurs in nearly 62% of people with Lewy body dementia, but in only 19% of people with Alzheimer's and in 6% of healthy older adults. Someone who talks loudly in their sleep, when that symptom stands alone, has a high probability that it is Lewy body dementia rather than Alzheimer's.

Not everyone with a REM sleep behaviour disorder develops symptoms equally quickly. Those who also have motor problems, a reduced sense of smell, mild memory problems or erectile dysfunction face a considerably higher risk of becoming ill more rapidly. These are therefore the combinations to watch out for.

If you or your partner suffer from this REM sleep behaviour disorder, there are treatment options: clonazepam or melatonin can reduce the nocturnal behaviour and protect the bed partner's sleep. However, a drug that slows or prevents the underlying brain disease does not yet exist.