Does fragmented sleep cause cognitive decline?
Yes. Adults with fragmented sleep show faster cognitive decline over years compared to peers with consolidated sleep, even when total sleep time is similar.
Quality matters, not just quantity
Studies tracking older adults with actigraphy have found that sleep fragmentation (frequent wake-ups, micro-arousals) predicts faster decline in memory and processing speed independent of total time in bed.
The dementia link
Several large cohort studies show fragmented sleep in midlife is associated with elevated risk of later dementia. Causality is debated but the association is robust.
Protective action
Treat the causes of fragmentation: untreated apnea, late alcohol, irregular schedule. Consistent wake-up time is foundational.
Sources
- Matthew Walker, Why We Sleep (Scribner, 2017). Why We Sleep: Unlocking the Power of Sleep and Dreams
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