You may already know that poor sleep is associated with a higher risk of dementia – and this seems to be especially true in midlife.
But what exactly does “poor sleep” mean?
Well, we know that sleeping more or less than seven to eight hours a night seems to be linked to the condition (though it can be hard to work out whether the condition causes the symptom or vice versa).
And “frequent” daytime napping that an older person doesn’t mean to take is also tied to greater odds of developing dementias like Alzheimer’s.
Meanwhile, according to a University of Arizona and University of Southern California paper, three sleep habits in midlife were associated with greater white matter hyperintensity (WMH).
What does white matter hyperintensity mean?
On an MRI scan, areas of WMH appear as white patches. They are “common by midlife and are seen in many older adults… [and] are often related to age-associated changes in the brain’s small blood vessels”, the Mayo Clinic shared.
WMHs could indicate “lesions” on the brain. Sometimes, they may predict a higher likelihood of dementia and stroke, per the BMJ.
They have also been linked to premature brain ageing.
Which sleep habits might lead to greater WMH volume?
In this study, researchers looked at survey responses and medical data from over 23,000 middle-aged and older adults.
From 2006 to 2010, participants filled in questionnaires which asked them about their:
- Sleep duration,
- Daytime napping,
- Sleeplessness,
- Unintentional daytime napping, and
- Snoring.
Roughly nine years later, participants were given an MRI scan and the study authors compared their answers throughout the study to the volume of WMH in their brains.
All five factors seemed to be linked to greater WMH at first glance. But after adjusting for confounding factors like smoking status, high blood pressure, and a lack of exercise, three signs seemed most significant:
- Sleeping more or less than seven to nine hours a night,
- Frequent daytime napping,
- Greater sleeplessness.
Those who slept for less than seven hours a night were found to have greater WMH volume in a follow-up analysis.
Professor Gene Alexander, the study’s senior author, said: “Our findings suggest that having too little sleep may lead to greater white matter lesion volumes in the brain as we age.
“We didn’t see greater white matter impacts in people who reported longer sleep durations, but this needs to be followed up in cohorts with more long sleepers.”
This study only showed an association between self-reported sleep patterns and WMH volume. That means it couldn’t prove for sure that they definitely led to this result.
But Prof Alexander ended, “Sleep is one of those potentially modifiable risk factors. If we can improve the quality of our sleep, it may help reduce the impacts of brain ageing and maybe even lower the risk [of] dementias like Alzheimer’s disease”.
