Sleep deprivation and depressive symptoms have been shown to negatively impact cognitive function within older adult populations (Gilley, 2022; Donovan et al., 2016). However, there is minimal research on interactions between sleep disturbance and depressive symptoms in relation to their shared impact on cognitive impairment. The purpose of this study is to examine possible interactions between sleep disorders and depression and their relationship with cognition among relatively good functioning and healthy older adults.

The sample was obtained from the Memory and Aging Project (Rush Alzheimer's Disease Center, Rush University, 2019) and consisted of 3,345 community dwelling older adults. The study analyzed data from 2552 women (76.3%) and 1093 men (23.7%). The average age of participants was 80 years and ranged from 45 to 98 years old. Measures used included the Berlin Questionnaire (risk for sleep apnea), Center for Epidemiological Studies Depression Scale (CES-D; depression), and a neuropsychological battery (visuospatial ability/perceptual reasoning and processing speed).

ANOVA analyses exhibited a significant main effect of depression on visuospatial ability/perceptual reasoning (p <.001), processing speed (p <.001), and semantic memory (p <.001). No significant main effect was found for sleep apnea on these cognitive domains. However, when sleep apnea was analyzed between those with any depressive symptoms versus those without, significant interactions were found for visuospatial ability/perceptual reasoning (p =.027), processing speed (p <.001), and semantic memory (p =.016). Sleep apnea symptoms had a greater detrimental effect on visuospatial skills and perceptual reasoning (F=4.90; p=.027) only when any depression symptom is present. In contrast, there was a steeper decline of processing speed when only depressive symptoms were present apart from sleep apnea symptoms (F=10.34; p =.001) Similarly, depressive symptoms had a greater negative effect on semantic memory for older adults who reported no sleep apnea symptoms compare to those who did (F=5.83, p=.016).

The current study indicated that while sleep apnea was negatively related to several cognitive domains, the impact became greater with the presence of depression on visuospatial skills and perceptual reasoning among older adults. However, the detrimental impact of sleep apnea was somewhat less with the presence of depression for processing speed and semantic memory. This may be due to likely higher endorsements of depressive symptoms compared to sleep apnea symptoms within the study sample. These findings suggest that there are differential interactive effects of sleep impairment and depressive symptoms on cognitive domains among older adults. Considering the relationship that exists between depression and increased disease burden among older adults, it is crucial for clinicians to also take sleep behaviors into account when examining and treating their patients. Clinicians should be mindful of their older patient's sleep health and depression measures when cognitive declines are suspected. They also suggest that cognitive performance may be improved with treating any symptoms of sleep apnea and depression in older adults.