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Depression and insomnia are prevalent in older adults and show bidirectional relationships. Sleep initiating and maintenance difficulties are the two frequently seen complaints of insomnia diagnostic criteria. Whether these two sleep complaints differ in their associations with depression is unknown. Using the National Health and Aging Trends Study (NHATS), we examined whether sleep initiating and maintenance difficulties at baseline (T1) predicted depression onset at 12 months (T2) and 24 months (T3) in 4,048 T1 non-depressed participants and whether depression at T1 predicted these two sleep complaints at T2 and T3 in 3,581 T1 non-insomnia participants. Participants who developed depression at T2 tended to be Hispanic, non-Hispanic black, less educated, live alone, physically inactive, and have more painful locations and chronic conditions. Participants with sleep complaints at T2 tended to be less educated, live alone, physically inactive, and have more painful locations and chronic conditions. Sleep initiating difficulty persistently predicted depression onset at T2 (OR: 1.62, 95% CI: 1.14, 2.31) and T3 (OR: 1.84, 95% CI: 1.21, 2.81) after adjusting demographics, lifestyles and health condition-related covariates. Depression at T1 persistently predicted sleep initiating difficulty at T2 (RRR: 2.19, 95% CI: 1.44, 3.34) and T3 (RRR: 1.70, 95% CI: 1.07, 2.70) after adjustment. Sleep maintenance difficulty at T1 did not predict depression onset at either time point and vice versa. This study suggests a bidirectional association of depression with sleep initiating difficulty but not sleep maintenance difficulty in older adults. Interventions targeting difficulty initiating sleep may moderate depression onset in older adults.

Poor sleep is common among older adults with Mild Cognitive Impairment (MCI) and may contribute to their increased risk for dementia. Chronotherapy is a set of intervention strategies which can improve sleep quality by strengthening the entrainment of the biological clock to the solar light-dark cycle, and includes strategies such as: 1) bright light therapy (BLT); 2) physical activity (PA); and 3) good sleep hygiene. Thus, in this 24-week randomized controlled trial (RCT; NCT02926157), we aimed to examine the efficacy of a multimodal, personalized chronotherapy intervention to improve sleep quality among older adults with MCI. Ninety-six older adults (65+ years) with MCI were randomized to either: 1) a multimodal personalized chronotherapy group (INT); or 2) a waitlist-plus-education control group (CON). Participants allocated to the INT received four once-weekly, general sleep hygiene education classes, followed by 20 weeks of 1) individually-timed BLT; and 2) bi-weekly, individually-tailored PA counselling in conjunction with receiving a consumer-available PA tracker (Fitbit® FlexTM). We found a significant group x time interaction for objectively measured sleep fragmentation (5.01; p< 0.01) and also for Pittsburgh Sleep Quality Index (PSQI) score (p= 0.03), such that the INT: 1) maintained sleep fragmentation while CON worsened at 12 weeks (p< 0.01); and 2) had improved PSQI score compared to CON at both 12 weeks (p< 0.01) and 24 weeks (p= 0.04). Our results provide novel evidence that a multimodal personalized chronotherapy approach may promote both objective and subjective aspects of sleep quality in older adults with MCI.