Whether it’s too little or it's poor quality, sleep disorders and risk of dementia have become increasingly linked, and scientists are racing to find out exactly how.
Sleep’s restorative properties are well known, and one of its roles is clearing out a build-up of beta-amyloid plaques in the brain – one of the two most common hallmarks of Alzheimer’s disease. And existing evidence draws a line between dementia risk and issues such as disrupted sleep, brief bouts of sleep deprivation and long-term insomnia.
Now, a new study has turned up some more bad news for those who struggle to nod off at night or take medication to do so, but also some surprising results for sleepers who wake during the night and don’t settle easily again.
“We expected sleep-initiation insomnia and sleep medication usage to increase dementia risk, but we were surprised to find sleep-maintenance insomnia decreased dementia risk,” explained lead investigator Roger Wong, an assistant professor in the Department of Public Health and Preventive Medicine, SUNY Upstate Medical University, Syracuse.
The study looked at 10 annual waves of data from the National Health and Aging Trends Study (NHATS), offering vital longitudinal analysis that sheds light on cognitive decline over time. The data was gathered from a nationally representative sample of 6,284 community-dwelling Medicare recipients aged 65 years and older and only included those who were dementia-free in 2011. Around 13.6% of the contributors received a dementia diagnosis in the time frame studied.
And despite previous evidence linking poor quality of sleep and sleep disturbances with dementia risk, the findings here also revealed that those with sleep-maintenance insomnia – difficulty falling back to sleep after waking – were less likely to develop dementia over this 10-year period of monitoring. It's unclear why, but the researchers hope further studies into disruptions and overall length of sleep will offer clues.
However, the older adults suffering from frequent sleep-initiation insomnia – trouble falling asleep within 30 minutes of turning off the lights – or using sleep medication, had an increased risk of dementia.
“Our findings highlight the importance of considering sleep disturbance history when assessing the dementia risk profile for older adults,” said Wong. “Future research is needed to examine other sleep disturbance measures using a national longitudinal sample, whether these sleep-dementia findings hold true for specific dementia subtypes, and how certain sociodemographic characteristics may interact with sleep disturbances to influence dementia risk.”
This research into long-term sleep disturbance is the first to use a nationally representative older adult sample. And with a high prevalence of disrupted sleep among older adults compared to other age groups, it underpins the importance of research that centers on those who are on the frontline of cognitive decline.
“By focusing on the variations in sleep disturbances, our findings can help to inform lifestyle changes that can reduce dementia risk,” explained co-investigator Margaret Anne Lovier, also of SUNY Upstate Medical University in Syracuse.
“Older adults are losing sleep over a wide variety of concerns,” added Wong. “More research is needed to better understand its causes and manifestations and limit the long-term consequences.”
The study was published in the American Journal of Preventative Medicine.
Source: Elsevier
