Sleep regularity may be a risk factor for dementia among older individuals.
Inconsistent sleep patterns and sleep irregularity may be a risk factor for incident dementia among older individuals, according to study findings published in Neurology.
Researchers conducted a study in participants sourced from the UK Biobank, and reported on the link between sleep regularity and risk for incident dementia. The participants were recruited between 2006 and 2010.
The Sleep Regularity Index (SRI) was determined by averaging the likelihood of being in the same asleep/wake state at 2 time points which took place 24 hours apart, observed throughout a 7-day accelerometry period.
The final analysis comprised a total of 88,094 participants (average age, 65; 56% women) with a median follow-up period of 7.2 years. During this time, there were 480 cases of incident dementia. This group of participants demonstrated a median SRI of 60.
Available evidence suggested a non-linear relationship between SRI and the risk for dementia, displaying hazard ratios with a U-shaped pattern.
Dementia rates reached their highest point at lower SRI levels, decreased to a minimum around the median (SRI = 60), and then slightly increased with higher SRI levels.
When compared to the median SRI of 60, participants with an SRI at the 5th percentile (SRI = 41) had hazard ratios (HRs) of 1.53 (95% CI, 1.24–1.89).
Conversely, for individuals with an SRI at the 95th percentile (SRI = 71), the HR was 1.16 (95% CI, 0.89–1.50).
The association between SRI and dementia remained consistent throughout the follow-up period.
In a subgroup analysis consisting of 15,263 individuals who underwent brain magnetic resonance imaging (MRI), the researchers observed an inverted U-shaped association between SRI and volumes of gray matter (P =.038) and the hippocampus (P =.035). Volumes continued to increase until the SRI reached the median, after which they started to decrease.
The researchers also saw a similar association with reduced gray matter volume and hippocampal volume in individuals at the extremes of SRI.
They believe that “both extremes if the SRI are linked to adverse brain health outcomes.”
The conclusions drawn from this study may have limitations due to the association between SRI and dementia, potential influence from unmeasured confounding factors, and the possibility of reverse causation.
“Future studies are required because, even in individuals with normal sleep durations, improvement of sleep timing schedules may represent a potential target for the primary prevention of dementia,” the researchers concluded.
This article originally appeared on Neurology Advisor
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