The Association of Sleep Problems with Mild Cognitive Impairment in Older Adults in the United States (US): A Cohort Study




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Background: The neuroprotective aspects of sleep include improvement of memory, problem-solving, creativity, emotional processing, and judgment. Sleep problems lead to neurological damage in the hippocampus. People with sleep problems have a higher risk of developing MCI. Examining the association of sleep problems with MCI is important for surveillance and prevention efforts of dementia because MCI often leads to dementia in 10%-15% of older adults. Objective: To examine the association of type of sleep problems with MCI among older adults (age > 50 years) using Health and Retirement Study (HRS), a nationally representative prospective cohort of older adults in the US. Methods: We used baseline (2018) and follow-up (2020) data from the HRS. We restricted the analysis to adults aged 50 years or older at baseline, alive in 2020, and did not have dementia in baseline and follow-up. All sleep variables were measured at baseline and MCI was measured during the follow-up period. The dependent variable (MCI) was based on the composite measure (immediate word recall test, delayed word recall, the serial 7s, counting backward), and total scores between 7-11 represent MCI without dementia. Sleep variables were based on responses (most of the time, some, and rare/never) to the following questions: “How often do you have trouble falling asleep?”, “How often do you have trouble waking up during the night?”, “How often do you have trouble with waking up too early and not being able to fall asleep again?” and “How often do you feel rested in the morning?”. Rao- unadjusted associations were tested with Rao-Scott chi-square and adjusted associations were examined with multivariable logistic regressions. All analyses accounted for the complex survey design, and SAS 9.4 Survey procedures were used. Results: Overall, 49.1% had trouble falling asleep, 62.2% had trouble waking up, 46.1% waking up too early, and 84.1% did not feel rested in the morning. A higher percentage of adults with trouble falling asleep (18.6% vs.11.7%), trouble waking up(15.5% vs, 12.3%), and waking up too early(18.9% vs. 11.1%) had MCI compared to those without sleep problems. In logistic regression that adjusted for sex, age, race and ethnicity, living alone, education, employment, poverty, and health insurance, those with sleep problems had higher odds of MCI (trouble sleeping: aOR=1.28(95%CI:1.05 1.56), waking up too early: aOR=1.48(95%CI:1.14, 1.94) compared to those without sleep problems. However, these associations became statistically insignificant when adjusted for health status and depression. In the fully-adjusted logistic regression, never feeling rested in the morning was associated with lower odds of MCI (aOR= 0.71,95% CI=0.55, 0.91, P<0.01). Conclusion: Most older adults reported sleep problems in trouble waking up or not feeling rested in the morning. Our study adds to the conflicting evidence in the literature; some studies report no association between sleep disturbance and cognition while others even report slightly better cognitive functioning in those with sleep problems. Our study findings suggest that the association of sleep disturbances with MCI varies by type of sleep problems.