Stress has a negative impact on the cognitive activity of the human brain, encouraging memory-related problems. This was revealed by a new study from the Karolinska Institutet, published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association. While mentally stimulating activities and life experiences can improve cognition in patients with memory disorders, stress undermines this beneficial relationship.
Research at the end of the 1980s
In the late 1980s, researchers found that some individuals who showed no apparent symptoms of dementia during their lifetime had brain changes consistent with an advanced stage of Alzheimer’s disease. It has since been hypothesized that so-called cognitive reserve may explain this differential protective effect in individuals. Cognitively enriching and stimulating life experiences and behaviors, such as a higher level of education, complex jobs, ongoing physical and recreational activities, and healthy social interactions, help build cognitive reserve. However, high or persistent levels of stress are associated with reduced social interactions, a lower ability to engage in physical and recreational activities and an increased risk of dementia.
Stress and sleep disorders
Researchers at Karolinska Institutet have now examined the association between cognitive reserve, cognition and Alzheimer’s disease biomarkers in 113 participants from the memory clinic at Karolinska University Hospital, Huddinge, Sweden. Furthermore, scientists examined how this association is modified by physiological stress, thanks to cortisol levels in saliva, and by psychological stress, i.e. perceived stress. Greater cognitive reserve was found to improve cognition, but interestingly, physiological stress appears to weaken the association. “These findings could have clinical implications, as a growing body of research suggests that mindfulness exercises and meditation can reduce cortisol levels and improve cognition,” said Manasa Shanta Yerramalla, a researcher in the Department of Neurobiology, Human Sciences. Care and Society of Karolinska Institutet and lead author of the study. “Different stress management strategies could be a good complement to existing lifestyle interventions in Alzheimer’s prevention,” Yerramalla continued. The relatively small sample of participants reduces the ability to draw robust conclusions, but the findings are generalizable to similar patient groups. Additionally, because stress alters sleep, which in turn alters cognition, the researchers controlled for sleep medications; however, they did not consider other aspects of sleep that could impair cognition. “We will continue to study the association between stress and sleep disturbances and how it affects cognitive reserve in memory clinic patients,” Yerramalla said.
