Study finds quality of sleep is linked to dementia and says one change could reduce risk

Experts say recommendations tend to focus on amounts of sleep rather than maintaining regularity

People with very irregular sleep patterns may have a high risk of developing dementia, a new study found.

The findings, published on Wednesday in the journal Neurology, revealed the regularity of a person’s sleep – ie going to sleep and waking up at the same time each day – is an important factor behind a person’s risk of dementia.

“Sleep health recommendations often focus on getting the recommended amount of sleep, which is seven to nine hours a night, but there is less emphasis on maintaining regular sleep schedules,” study author Matthew Paul Pase from Monash University in Australia said.

While previous studies have linked irregular sleep with metabolic conditions and heart health, its association with incident dementia has however remained unclear.

In the latest research, scientists assessed the health data of over 88,000 people in the UK with an average age of 62, following them for an average of seven years.

Researchers calculated the regularity of their sleep – their day-to-day consistency in sleep-wake patterns – based on data from a wrist device the participants wore that measured their sleep cycle for about a week.

They estimated the probability of the participants being in the same sleep state – asleep or awake – at any two time points 24 hours apart, averaged over the seven days.

Participants who slept and woke up at the same time each day had a sleep regularity index of 100, while those who slept and woke up at different times had a score of zero.

About 480 people in the study developed dementia.

Probing the link between sleep regularity scores and dementia risk, scientists found that the risk of the neurological condition was highest for those with the most irregular sleep.

Individuals in the lowest fifth percentile had the most irregular sleep with an average score of 41 while the highest 95^th percentile had the most regular sleep with an average score of 71.

Participants between these two groups had an average sleep regularity score of 60, the study noted.

“Based on our findings, people with irregular sleep may only need to improve their sleep regularity to average levels, compared to very high levels, to prevent dementia. Future research is needed to confirm our findings,” Dr Pase said.

Citing limitations of the research, scientists said they cannot rule out that another unknown factor may play a role in the link between sleep regularity and dementia.

The study also does not prove that sleep irregularity causes dementia but only shows an association, researchers said.