Duration of night sleep and cognitive performance of community older adults.
Élen Dos Santos Alves, Sofia Cristina Iost Pavarini, Bruna Moretti Luchesi and 3 others
PMID 34190939WHAT IT FOUND
Sleeping more did not mean better thinking for these older adults.
While total sleep length showed no link to overall cognitive scores, those who slept the longest had lower verbal fluency scores than those who slept less. Education level was the strongest predictor of cognition.
Key findings
01There was no significant difference between sleep duration groups in total cognitive scores or in attention, memory, language, and visuospatial domains.
02Older adults who slept the most (mean 8.85 hours) had lower verbal fluency scores than those who slept less (means 6.11 and 4.52 hours).
03In the adjusted model, schooling and hours of sleep remained significant predictors for verbal fluency, but schooling was the only predictor for total cognition.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study used a small, non-probabilistic sample from a single municipality, limiting generalizability. Sleep duration was self-reported, which is subject to recall bias and less accurate than objective measures like actigraphy. The cross-sectional design cannot determine causality; it is unclear if long sleep causes lower fluency or if underlying health issues cause both. Education level was a very strong predictor of cognition, which may confound the relationship between sleep and cognitive performance. The finding regarding verbal fluency was a secondary domain analysis; the primary outcome of total cognitive performance was null.
Declared interests
The authors declared no conflicts of interest. The study was supported by CNPq and FAPESP grants.
The easy way to misread this
Do not conclude that sleeping too much causes cognitive decline. This is a cross-sectional study, so it cannot prove cause and effect. The association with verbal fluency was a secondary finding, while the primary outcome of total cognition showed no relationship with sleep duration. Furthermore, education level was a much stronger predictor of total cognitive scores than sleep.