Which sleep measure was most strongly linked to cognition in older adults?

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Researchers examined how sleep quality relates to cognitive abilities in later life and which sleep measures are most closely associated with specific cognitive domains. This cross-sectional study involved community-dwelling adults aged 65 and older in the Copenhagen metropolitan area of Denmark. Participants were recruited from primary care practices and senior community centers between February 2019 and November 2020; 523 completed comprehensive sleep and cognitive assessments at the Danish Center for Sleep Medicine at Rigshospitalet.

The Pittsburgh Sleep Quality Index assessed the preceding month’s subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, sleep medication use, and daytime dysfunction. The Montreal Cognitive Assessment examined attention, executive function, memory, language, visuospatial abilities, and orientation.

Overall, 47.2% of participants had poor sleep quality, defined as a Pittsburgh Sleep Quality Index score above five; they scored significantly lower than good sleepers across all measured cognitive domains. In multiple regression controlling for age, education, depression, and medical comorbidities, sleep quality independently predicted cognitive performance: each one-point increase in the Pittsburgh score was associated with a 0.34-point decrease in the Montreal score. Of the seven sleep measures, sleep efficiency was the strongest individual predictor of cognitive function, followed by sleep duration and severity of daytime dysfunction. Poor sleep was particularly strongly associated with executive function deficits; associations with memory and processing speed were weaker but still significant.

Participants who met screening criteria for mild cognitive impairment had substantially worse sleep quality profiles than cognitively normal participants; the authors suggested that sleep disturbance and cognitive decline may have a bidirectional relationship that requires further longitudinal investigation. The authors concluded that sleep quality assessment and intervention are important in geriatric practice because sleep quality may be a modifiable risk factor for cognitive decline. They recommended routinely screening older patients for sleep disturbances and considering sleep optimization as part of comprehensive cognitive health promotion for Denmark’s aging population.