Named a type of insomnia that reduces the risk of dementia. But why is unknown.

Scientists have long known about the connection between sleep disorders and dementia. But exactly how one influences the other is unclear.

The authors of a new study tried to answerto this question. “The type of insomnia associated with sleep maintenance appeared to reduce the risk of developing dementia,” explained Roger Wong, lead researcher and assistant professor of public health and preventive medicine at SUNY Upstate.

The study authors examined the datafrom a representative sample of 6,284 users of Medicare, the national health insurance program in the United States for individuals 65 years of age and older. Study subjects were people without dementia as of 2011. Ultimately, over the next 10 years, about 13.6% of participants received a diagnosis of dementia.

Despite previous data linkingpoor sleep quality and sleep disturbances with a risk of developing dementia, the results obtained differed from the norm. People who had difficulty falling asleep after waking up in the middle of the night were less likely to develop dementia over a 10-year period. Why this happens is unclear, but researchers hope that further studies of disturbances and overall sleep duration will help provide an answer.

However, older people sufferingProblems falling asleep within 30 minutes of turning off the lights were most likely to be diagnosed with dementia within the next 10 years.

"Our results highlight the importance of taking into account a history of sleep disturbances when assessing the risk profile of dementia in the elderly," the researchers conclude.

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