Sleep Characteristics in Older Adults with Different Levels of Risk for Dementia: A Cross-sectional Study

Background: Sleep problems are very prevalent in older adults, especially in those at risk for dementia. But the relationships between sleep parameters and subjective or objective cognitive decline are still inconclusive. Aim: The study aimed to investigate the self-reported and objectively measured sleep characteristics in older adults with mild cognitive impairment (MCI) and subjective cognitive decline (SCD). Methods: This study adopted a cross-sectional design. We included older adults with SCD or MCI. Sleep quality was measured separately by the Pittsburgh sleep quality index (PSQI) and ActiGraph. Participants with SCD were divided into low, moderate, and high levels of SCD groups. Independent samples T-tests, one-way ANOVA, or nonparametric tests were used to compare the sleep parameters across groups. Covariance analyses were also performed to control the covariates. Results: Around half of the participants (45.9%) reported poor sleep quality (PSQI＜7), and 71.3% of participants slept less than 7 hours per night, as measured by ActiGraph. Participants with MCI showed shorter time in bed (TIB) (p＜0.05), a tendency of shorter total sleep time (TST) at night (p = 0.074) and for each 24-hour cycle (p = 0.069), compared to those with SCD. The high SCD group reported the highest PSQI total score and longest sleep latency than all the other three groups (p＜0.05). Both the MCI and high SCD groups had shorter TIB and TST for each 24-hour cycle than the low or moderate SCD groups. Besides, participants with multiple-domain SCD reported poorer sleep quality than those with single-domain SCD (p＜0.05). Conclusion: Sleep dysregulation is prevalent in older adults with a risk for dementia. Our findings revealed that objectively measured sleep duration might be an early sign of MCI. Individuals with high levels of SCD demonstrated poorerself-perceived sleep quality and deserved more attention. Improving sleep quality might be a potential target to prevent cognitive decline for people with a risk for dementia.