Sleep problems contribute to a variety of psychological and physical problems. But is the cognitive functioning of sleep-impaired people with depression worse than those without depression? A researcher from the University of Zurich in Switzerland sought to answer that question in a recent study “Sleep Quality and Cognitive Function in Healthy Old Age: The Moderating Role of Subclinical Depression” published in Neuropsychology.
As people age, they tend to experience weaker cognition as well as more sleep difficulties. Although the relationship between these has been studied in depth, few studies have focused on how depression moderates the effect of sleep disturbance on memory, cognitive speed and processing in older adults.
For the study, researcher Christine Sutter recruited adults over the age of 61. She included 107 adults with and without depression and evaluated their sleep patterns using the Pittsburgh Sleep Quality Index. The volunteers worked on a series of tasks that measured their executive function processing, speed, and memory recall.
The researchers found that the participants with higher levels of depressive symptoms and sleep problems had a harder time completing the cognitive tasks than those with fewer depressive symptoms and more moderate sleep problems. Although many areas of executive function were affected by depression and sleep disturbances, memory recall related to specific events was not. This suggests that a lack of sleep weakens higher-order executive functions, especially in people who have depression. A lack of sleep can trigger problems with mood regulation. Therefore, the depressive symptoms in this sample of participants could be magnified by less sleep. Future research should examine the slight variations in the sleep/mood relationship in more detail.
Although psychotropic medication was accounted for in this study, other drugs that could influence the outcome were not. This is yet another area that must be looked at more closely to better understand the association between sleep disturbances, mood, and cognitive performance, Sutter said. She added that overall, the study results demonstrate a clear link between sleep impairment and executive processing in older individuals.
“However, it also seems important to consider low levels of depressive symptomatology together with sleep quality, as they appear to be interrelated,” Sutter said.