Disrupted Sleep in 30s and 40s Linked to Cognitive Problems a Decade Later

Yue Leng, PhD

Credit: University of California San Francisco

People in their 30s and 40s who have disrupted sleep could be at a greater risk of memory and thinking problems a decade later, according to a new study published in Neurology.1

Results of the study, which included 11 years of follow-up data from more than 500 participants, suggest increased sleep disruption was linked to an increased risk of worsening executive function among middle-aged adults from within the Coronary Artery Risk Development in Young Adults (CARDIA) cohort study.

“Among middle-aged Black and White adults, actigraphy measured high sleep fragmentation in early midlife was independently associated with worse executive function, fluency, and global cognition approximately 11 years later; a threshold seems to exist with the degree of sleep fragmentation,” the investigators wrote. “No association was found for sleep duration or self-reported sleep quality.”

Citing previous research linking sleep quality and duration to conditions such as Alzheimer disease and dementia among older adults, a team led by Yue Leng, PhD, from the University of California in San Francisco, sought to evaluate the impact of these factors among younger adults on cognition in midlife. With this in mind, investigators conducted an analysis leveraging data from the CARDIA study, which provided investigators with data from more than 500 individuals with sleep duration and quality data from their mid-30s to late 40s as well as midlife cognition assessments 11 years later.^1,2

As part of the CARDIA study, participants underwent assessments of sleep duration and quality using the Pittsburgh Sleep Quality Index (PSQI) and wrist actigraphy from 2003 to 2005. More than a decade later, between 2015 and 2016, participants underwent assessments of midlife cognition using the Digit Symbol Substitution Test, Stroop test, Rey Auditory Verbal Learning Test (RAVLT), Montreal Cognitive Assessment (MOCA), and Letter Fluency and Category Fluency tests. In the current study, investigators used multivariable logistic regression to evaluate the association between sleep parameters and poor cognitive performance.

The 526 participants had a mean age of 40.1 ± 3.6 years at baseline, 58% were women, and 44% were Black. The mean sleep duration was 6.1 ± 1.1 hours and the mean sleep fragmentation index was 19.2 ± 8.1%. Of note, more than half (54.6%) of participants reported poor sleep, receiving a PSQI global score of > 5.

Participants who had shorter sleep duration or higher sleep fragmentation were significantly more likely to be male, Black, have a higher BMI, and have a history of depression or hypertension. As for a poorer, subjective sleep quality, participants were more likely to be younger, female, Black, have a lower education, a higher BMI, lower physical activity, and had a history of depression or hypertension.

Participants on the highest tertile of sleep fragmentation index, compared to the lowest tertile (< 15.3), were 3 times more likely to have poor cognitive performance at midlife on the DSST (Odds ratio [OR], 3.32; 95% CI, 1.52 – 7.21) and have at least double the odds of poor cognitive performance on the Stroop (OR, 2.29; 95% CI 1.09–4.83), fluency (OR, 2.78; 95% CI, 1.37–5.64), and MOCA test (OR, 2.20; 95% CI, 1.05–4.59). A trend toward increased odds on RAVLT (OR, 1.39; 95%CI, 0.76–2.54) was also observed.

The investigators noted no differences in cognitive performance at midlife for participants in moderate sleep fragmentation index categories. Additionally, compared to participants with good sleep quality (PSQI ≤ 5), those with poor sleep quality (PSQI > 5) had 83% greater odds of having poor cognitive performance on the Stroop test (OR, 1.82; 95% CI, 1.02 – 3.26).

After adjusting for demographics, education, smoking, BMI, depression, physical activity, hypertension, and diabetes, the participants who had the highest sleep fragmentation index were double more likely to have a poor cognitive performance on the Digit Symbol Substitution Test (OR, 2.97; 95% CI, 1.34 – 6.56), Letter Fluency and Category Fluency tests (OR, 2.42; 95% CI, 1.17 – 5.02), and Montreal Cognitive Assessment (OR, 2.29 95%; CI, 1.06 – 4.94). Sex or race did not alter the association between sleep fragmentation and cognitive performance.

Some limitations in the study highlighted by investigators include the lack of polysomnography measures of sleep, only measuring sleep for 6 days—thus not enough data to compare weekday and weekend sleep—the small sample size, and only assessing participants 11 years later and therefore not assessing cognition even later in life.

“Our findings indicate that the quality rather than the quantity of sleep matters most for cognitive health in midlife and that the measures of sleep should go beyond self-report,” investigators wrote. “Future research is needed to assess the association between sleep disturbances and cognition at different stages of life and to identify whether critical life periods exist when sleep is more strongly associated with cognition.”

^References

1. ^{Leng Y, Knutson K, Carnethon MR, Yaffe K. Association Between Sleep Quantity and Quality in Early Adulthood With Cognitive Function in Midlife. Neurology. 2024;102(2):e208056. doi:10.1212/WNL.0000000000208056}
2. ^{Understanding the Connection Between Sleep and Dementia. Harvard Pilgrim Health Care. https://www.harvardpilgrim.org/hapiguide/understanding-the-connection-between-sleep-and-dementia/#:~:text=A%20different%20study%20of%20nearly,sleep%20duration%20of%20seven%20hours. Accessed January 8, 2024.}