Sleep and dementia seem to have a complicated relationship. They do seem to be linked, but it can be very hard to work out whether the condition causes the symptom or vice versa. It may be a mix of both.
Some research suggests that while sleeping for a minimum of seven or eight hours a night may be associated with a lower likelihood of developing dementia, over-65s who kip for longer – eight and a half hours or more – might face a higher risk. The other extreme (insomnia) is linked to 40% greater odds of ending up with mild cognitive impairment, sometimes seen as a precursor to conditions like Alzheimer’s.
A brain primed for dementia might also struggle to clear waste effectively during sleep, one paper found.
And now, research published in The Journal of Gerontology: Medical Sciences has suggested that our napping habits could be associated with a 48% higher dementia risk, too.
Daytime napping appears to be associated with dementia
This study looked at 995 adults who were over 65 and were part of the US Medicare programme.
The study began in 2010, and participants’ health was tracked across a decade.
The researchers also looked at their napping habits. And they grouped people’s sleep patterns by:
Frequency (how often participants’ nodded off during the day), Intention (whether people who napped meant to do so, or if it happened accidentally), and Duration (how long the naps lasted).
After comparing these results, researchers found that frequent nappers, who caught some midday Zzzs most days of every day, had a 48% higher chance of developing dementia compared to non-nappers.
Unintentional nappers, who napped without really meaning to, saw a 39% greater risk, and napping for 30 minutes or less was associated with 40% increased odds.
These results stood even when researchers took people who had recieved dementia diagnoses within five years of the study’s start time – i.e., people who might have different sleep patterns due to early undiagnosed dementia – out of the picture. That might mean the sleep change could show up before clearer signs of dementia do.
The paper concluded, “frequent and unintentional napping were associated with a higher risk of developing incident possible/probable dementia over 10 years”.
The relationship may still be two-way
Dr Adam Spira, a senior author of the paper and professor in the Bloomberg School’s Department of Mental Health, said: “More frequent napping could be a marker of changes in the brain, rather than a cause of brain changes that lead to dementia”.
Additonally, this paper only showed an association and not a cause. It doesn’t prove that napping of any kind definitely causes dementia.
This is not, however, the link between daytime napping and conditions like Alzheimer’s. Professor Dr Rayaz Malik previously said: “Taking frequent daytime naps is also a notable behaviour associated with certain conditions, including dementia, and losing interest in friends and family is a sign that may indicate dementia”.
And Dr Susan Mitchell, Head of Policy from Alzheimer’s Research UK, also said, “Unusual sleep patterns are common for people with dementia, but research suggests that sleep changes could be apparent long before any symptoms like memory loss start to show”.