Stress Effects on the Aging Brain
By Cameron, BSc Neuroscience
When a stressful situation occurs, the brain immediately responds. Stress causes two different bodily reactions. The first is the activation of the ‘fight-or-flight’ system, which alters blood pressure, heart rate, and breathing rate. The second involves the release of a glucocorticoid called cortisol into the bloodstream. Cortisol is also capable of traversing the blood-brain barrier, where it enters the brain and binds to receptors in regions crucial for aspects of memory and cognitive control. These regions include the prefrontal cortex, amygdala, and the hippocampus (Mikneviciute et al., 2022). Stress itself can be categorized as either ‘acute stress’ or ‘chronic stress’.
ACUTE STRESS
Acute stress can be thought of as a short-term or relatively light period of stress. The brain attempts to direct attention towards the object causing the stress. As such, the brain’s capacities are altered and certain cognitive functions may be enhanced, while others may be hindered. In older adults, the areas of working memory and response inhibition are momentarily enhanced by short-term periods of stress. While these functions seem to be enhanced, other functions, like verbal fluency and risk-taking capabilities are hindered. Additionally, long-term memory and cognitive control may be caught in the middle of these two extremes, with results switching from being relatively unaffected, to being negatively affected by acute stress. The negative effects of acute stress can be exacerbated, and its enhancing effects diminished, if the amount of acute stress creates too high a cognitive load for the brain to handle (Mikneviciute et al., 2022). Such high amounts of stress can be considered as chronic stress.
CHRONIC STRESS
Chronic stress, also referred to as long-term or severe periods of stress, is more toxic to the brain. While relatively well-equipped to handle short-term stress (Mikneviciute et al., 2022), prolonged exposure to stress can begin to overwork or ‘burn out’ the brain across all age groups. Chronic stress has been linked to neurodegeneration (Leight et al., 2023), and is considered to play an important role in the progression of Alzheimer’s Disease (Saeedi and Rashidy-Pour, 2021). A somewhat surprising result of chronic stress, is its effect on the gut, also known as the Enteric Nervous System (ENS). The effects of chronic stress on the ENS include: impaired gut functioning, reduced mucus layer thickness, suppressed immunity, and increased amounts of detrimental bacteria alongside decreased number of beneficial bacteria (Leigh et al., 2023). Individuals with chronic stress are more likely to develop Inflammatory Bowel Disease than those without chronic stressors (Schneider et al., 2023).
Two potential ways to help reduce stress are engaging in social relationships and cognitive reappraisal exercises. A study looking at the effects of social relations on stress, found that older adults who had positive relationships with others reported the least amounts of stress (Ellwardt et al., 2020). As well, cognitive reappraisal exercises may assist in helping individuals find ways to reduce perceived stress in their lives. Two exercises in the study were reflections on past resilience and post-stressor visualizations. Examples of these are, respectively, ‘How have you come through hard times before?’ and the exercise of ‘imagining a return to “normal life”’ (Whitehead, 2021)
REFERENCES
Doerfler, T. (2018). [Photograph] Man holding Chin https://unsplash.com/photos/man-holding-chin-dYNar7pk9_Y
Ellwardt, L., Wittek, R.P.M., Hawkley, L.C., Cacioppo, J.T. (2020). Social Network Characteristics and Their Associations With Stress in Older Adults: Closure and Balance in a Population-Based Sample. Journals of Gerontology: Social Sciences, 75(7), 1573-1584. doi:10.1093/geronb/gbz035
Leigh, S., Uhlig, F., Wilmes, L., Sanchez-Diaz, P., Gheorghe, C.E., Goodson, M.S., Kelley-Loughnane, N., Hyland, N.P., Cryan, J.F., & Clarke, G. (2023). The impact of acute and chronic stress on gastrointestinal physiology and function: a microbiota-gut-brain axis perspective. The Journal of Physiology, 601(20), 4491-4538. DOI: 10.1113/JP281951
Mikneviciute, G., Ballhausen, N., Rimmele, U., & Kliegel, M. (2022). Does older adults’ cognition particularly suffer from stress? A systematic review of acute stress effects on cognition in older age. Neuroscience and Biobehavioral Reviews, 132, 583-602. https://doi.org/10.1016/j.neubiorev.2021.12.009
Saeedi, M., & Rashidy-Pour, A. (2021). Association between chronic stress and Alzheimer’s disease: Therapeutic effects of Saffron. Biomedicine & Pharmacotherapy, 133, 1-9. https://doi.org/10.1016/j.biopha.2020.110995
Schneider, K.M., Blank, N., Alvarez, Y., Thum, K., Lundgren, P., Litichevskiy, L., Sleeman, M., Bahnsen, K., Kim, J., Kardo, S., Patel, S., Dohnalová, L., Uhr, G.T., Descamps, H.C., Kircher, S., McSween, A.M., Ardabili, A.R., Nemec, K.M., Jimenez, M.T., … Thaiss, C.A. (2023). The enteric nervous system relays psychological stress to intestinal inflammation. Cell, 186(13), 2823-2838. https://doi.org/10.1016/j.cell.2023.05.001
Whitehead, B.R. (2021). COVID-19 as a Stressor: Pandemic Expectations, Perceived Stress, and Negative Affect in Older Adults. Journals of Gerontology: Psychological Sciences, 76(2), 56-64. doi:10.1093/geronb/gbaa153