A cross-sectional study found that sleep duration may affect episodic memory, according to study findings published in the Journal of Sleep Research.
Sleep is an important component to healthy aging and cognitive function. Although this link has been well-established, it remains unclear what specific components of sleep and cognition are related. The objective of the current study was to examine cross-sectional and prospective associations between self-reported sleep and cognitive function in middle-to-older aged adults in the United States.
The Midlife in the United States (MIDUS) study surveyed 7108 American aged 25-74 years in 1995-1996. Since that time there have been 2 follow-ups in 2004-2006 (n=3,487) and 2013-2014 (n=3,294). This study assessed longitudinal outcomes of sleep and cognition among 2,375 of the participants who self-reported sleep duration on weekdays and weekends. Short sleep was defined as <7 hours, normal as 7-8 hours, and long as >8 hours. Cognition was assessed using the Brief Test of Adult Cognition by Telephone and Stop and Go Switch Task.
The participants were aged mean 54.71 (range, 28-84) years, 90.62% were White, 49.89% had some college or undergraduate degree, and 59.75% engaged in cognitive activity ³1 per month.
Individuals who reported shorter sleep on weekdays were younger, had lower education, were more likely to be men, non-White, and obese. Longer sleepers were more likely to be older, to have lower body mass index, lower education, and to engage in physical activities regularly.
Sleep quality scores were derived by the total number of sleep problems, forming 3 groups: quality scores of 0 (n=1,992), 1 (n=531), and ³2 (n=689).
There was a significant trend observed in the adjusted model between longer weekday (P =.04) and weekend (P =.04) sleep with lower episodic memory. Significant trends were not observed in the adjusted model for executive function or sleep quality scores.
Stratified by gender, men with short (b, -0.24; 95% CI, -0.37 to -0.12) and long (b, -0.13; 95% CI, -0.25 to -0.02) weekend sleep duration associated with lower composite cognitive scores.
Although not reaching significance, there was also a trend between longer weekend sleep and episodic memory among men and a positive relationship between weekend sleep and executive function among women.
For temporal trends, between the second and third MIDUS follow-ups, no associations were observed between sleep duration or quality and cognitive scores. Trends were similar among genders and age groups.
This study was limited as it was not a representative sample of the general population of the United States, skewing toward the White, educated population.
These data suggested that people with long sleep durations may have lower cognitive performance. This association likely affects men and women differently. Additional studies are needed to confirm these findings.
Schneider AC, Moon C, Whitaker KM, et al. Cross-sectional and prospective associations between self-reported sleep characteristics and cognitive function in men and women: The Midlife in the United States study. J Sleep Res. Published online November 11, 2021. doi:10.1111/jsr.13515