Cognitive aging is the process of gradual changes in cognitive functions that occur as people get older. Cognitive aging is a natural part of the human lifespan, but it comes with its own set of challenges. Cognitive decline is one of the major difficulties associated with aging, as it can affect various aspects of daily life, such as memory, attention, decision making, and problem solving. Non-invasive brain stimulation techniques, such as Transcranial Magnetic Stimulation (TMS), have emerged as promising tools to address cognitive decline in older adults. TMS may have the potential to enhance cognitive performance and slow down cognitive decline in older adults. TMS is a method of applying magnetic pulses to specific regions of the brain, which can change neural activity. TMS has been shown to improve cognitive functions in various domains, such as memory, language, executive functions, and spatial abilities, in both healthy older adults and patients with neurodegenerative diseases. This article will examine how TMS may offer a promising and safe intervention for mitigating the effects of cognitive aging and improving the quality of life of older adults.

Cognitive Decline

Cognitive decline is an inevitable aspect of aging, impacting many older adults to varying degrees. This gradual deterioration of cognitive abilities, such as memory, attention, reasoning, and problem-solving, can have profound effects on individuals’ daily lives, independence, and overall well-being. While not everyone will experience significant cognitive decline, it is prevalent among older adults. Cognitive decline can be influenced by various factors, such as genetics, lifestyle, education, health conditions, and medications. One of the most commonly observed changes is a decline in processing speed, making it take longer to complete cognitive tasks. Memory difficulties, such as forgetfulness and mild word-finding problems, are also common. Memory lapses and difficulties with attention can make it challenging to remember appointments, manage finances, or even follow a conversation. Older adults may become frustrated or anxious when they notice these changes, which can further impact their cognitive performance. Older adults may also find it harder to multitask and may become more easily distracted. These changes are typically mild and do not interfere significantly with daily life, but they can also have emotional consequences, leading to feelings of inadequacy or sadness. However, for some individuals, cognitive decline can progress to more severe conditions, such as dementia and Alzheimer’s disease.

While age-related cognitive decline is considered a normal part of aging, dementia represents a more severe and often pathological form of cognitive impairment. Dementia is an umbrella term encompassing various cognitive disorders characterized by significant cognitive decline that interferes with daily functioning. Dementia also affects the personality, emotions, and behavior of the affected individuals, who may experience hallucinations, delusions, paranoia, agitation, depression, and anxiety. Alzheimer’s disease is the most common cause of dementia, accounting for a significant portion of dementia cases. It is a progressive neurodegenerative disorder characterized by the accumulation of abnormal protein deposits in the brain, leading to the gradual decline of cognitive function.

Dementia, including Alzheimer’s disease, can have devastating effects on individuals and their families. As cognitive decline progresses, individuals may struggle with basic activities of daily living, such as dressing, bathing, and eating. Communication becomes increasingly challenging, leading to social isolation and frustration. Caregivers often shoulder a substantial burden, providing round-the-clock support and witnessing the gradual loss of their loved ones’ identity.

Cognitive Resilience

Cognitive resilience refers to the ability to maintain cognitive function and adapt to age-related changes effectively. While some individuals may be genetically predisposed to better cognitive resilience, lifestyle factors also play a crucial role. Engaging in cognitive-stimulating activities, maintaining physical fitness, following a balanced diet, and staying socially connected have all been associated with improved cognitive resilience.^{1, 2,3}

Moreover, emerging research suggests that interventions such as cognitive training, mindfulness practices, and non-invasive brain stimulation techniques like TMS may hold promise in bolstering cognitive resilience in older adults. These interventions aim to enhance cognitive function, potentially slowing the rate of cognitive decline and delaying the onset of more severe conditions like dementia and Alzheimer’s.

TMS and Cognitive Aging

TMS uses magnetic pulses to induce electric currents in specific regions of the cortex. TMS can influence cortical activity by either increasing or decreasing the excitability of neurons, depending on the frequency, intensity, and duration of the stimulation. TMS can also cause changes in the brain, such as synaptic strengthening, neurogenesis, and angiogenesis, which may counteract the effects of age-related brain cell death (atrophy). According to meta-analyses, TMS can stimulate the brain’s cortex and potentially improve cognitive functioning in various brain disorders, including dementia.⁴

TMS can enhance cognitive functioning by targeting specific brain regions that are involved in memory, attention, and executive functions. For example, TMS can improve memory by stimulating the medial temporal lobe, which is responsible for encoding and retrieving information. TMS can also improve attention by stimulating the dorsolateral prefrontal cortex, which is involved in selective and sustained attention. Moreover, TMS can improve executive functions by stimulating the anterior cingulate cortex, which is involved in conflict resolution, error detection, and cognitive control. By stimulating these brain regions, TMS can impact the neural networks that underlie cognitive processes and enhance their efficiency and performance.

Efficacy of TMS in Cognitive Aging

One of the cognitive domains that is most affected by aging is working memory, which is the ability to maintain and manipulate information in a short-term buffer. Working memory is essential for many complex cognitive tasks, such as reasoning, problem-solving, and decision-making, and its decline is a major factor in age-related cognitive impairment.⁵ Several studies have used TMS to enhance working memory in older adults, by targeting specific brain regions that are involved in working memory processes, such as the prefrontal cortex (PFC), the parietal cortex, and the cerebellum. Some of these studies have reported positive effects of TMS on working memory performance.⁵ These studies suggest that TMS can affect the neural activity of the working memory network and enhance its efficiency and capacity. However, other studies have found no or negative effects of TMS on working memory in older adults or have reported differential effects depending on the stimulation parameters, the task difficulty, or the individual characteristics of the participants.⁶ These studies indicate that the effects of TMS on working memory are promising, but require further investigation given the discrepancies between studies.

Several meta-analyses and systematic reviews have evaluated the overall efficacy of TMS in improving cognitive function in older adults, with mixed results. Some reviews have reported positive effects of TMS on various cognitive domains, such as memory, language, executive functions, and spatial abilities, in both healthy older adults and patients with neurodegenerative diseases.⁴ The literature suggests that TMS can stimulate the cortex and potentially prevent or delay cognitive decline in aging. A study found potential therapeutic benefits of TMS for cognitive impairment and neuropathic pain in the elderly.⁷ Another study of Alzheimer’s disease patients explored the diagnostic and therapeutic applications of TMS, showing that TMS measures can support clinical diagnosis and predict progression, and that TMS may improve cognition in Alzheimer’s disease patients.⁸ Another study of older adults found that TMS caused changes in how different parts of the brain communicate, such as becoming more active (excitation) or less active (inhibition).⁹Additionally, the study found that TMS affected the brain’s ability to learn and change (plasticity) and also influenced how the brain controls movements (motor control).⁹ In sum, this research suggests that TMS holds promise as a tool for cognitive resilience in aging.

Cognitive aging, marked by gradual changes in cognitive functions as people grow older, presents significant challenges to daily life and may progress to severe conditions like dementia and Alzheimer’s disease, affecting both individuals and their families profoundly.

However, cognitive resilience aims towards preserving the ability to effectively maintain cognitive function and adapt to age-related changes. Lifestyle choices, including engaging in cognitive-stimulating activities, maintaining physical fitness, and staying socially connected, play a vital role in reinforcing cognitive resilience. Furthermore, innovative interventions like TMS show promise in enhancing cognitive health among older adults.

TMS has demonstrated potential in improving cognitive performance and potentially delaying cognitive decline in older individuals. By targeting specific brain regions related to memory, attention, and executive functions, TMS can enhance neural networks, boosting cognitive efficiency and capacity. While research results vary, meta-analyses and systematic reviews suggest positive TMS effects across various cognitive domains. This offers hope for preserving cognitive function as individuals age. With ongoing research and the exploration of non-invasive brain stimulation techniques like TMS, the possibility of mitigating cognitive aging effects and enhancing the quality of life for older adults becomes increasingly promising.

References

1. Sherchan, P., Miles, F., Orlich, M. et al.Effects of Lifestyle Factors on Cognitive Resilience: Commentary on “What This Sunny, Religious Town in California Teaches Us About Living Longer”.  Stroke Res. 11, 161–164 (2020). https://doi.org/10.1007/s12975-020-00788-y
2. Grasset, L., Proust-Lima, C., Mangin, JF. et al.Explaining the association between social and lifestyle factors and cognitive functions: a pathway analysis in the Memento cohort. Alz Res Therapy 14, 68 (2022). https://doi.org/10.1186/s13195-022-01013-8
3. Pettigrew, C., Soldan, A. Defining Cognitive Reserve and Implications for Cognitive Aging. Curr Neurol Neurosci Rep19, 1 (2019). https://doi.org/10.1007/s11910-019-0917-z
4. Begemann, M., Brand, B., Ćurčić-Blake, B., Aleman, A., & Sommer, I. (2020). Efficacy of non-invasive brain stimulation on cognitive functioning in brain disorders: a meta-analysis. Psychological Medicine, 50(15), 2465-2486. https://doi.org/10.1017/s0033291720003670
5. Beynel, L., Davis, S. W., Crowell, C. A., Hilbig, S., Lim, W., Nguyen, D., … & Appelbaum, L. G. (2019). Online repetitive transcranial magnetic stimulation during working memory in younger and older adults: a randomized within-subject comparison. Plos One, 14(3), e0213707. https://doi.org/10.1371/journal.pone.0213707
6. Martins, A., Fregni, F., Simis, M., & Almeida, J. (2016). Neuromodulation as a cognitive enhancement strategy in healthy older adults: promises and pitfalls. Aging, Neuropsychology, and Cognition, 24(2), 158-185. https://doi.org/10.1080/13825585.2016.1176986
7. Iriarte, I.G., George, M.S. Transcranial Magnetic Stimulation (TMS) in the Elderly. Curr Psychiatry Rep20, 6 (2018). https://doi.org/10.1007/s11920-018-0866-2
8. Lazzaro, V. D., Bella, R., Benussi, A., Bologna, M., Borroni, B., Capone, F., … & Ranieri, F. (2021). Diagnostic contribution and therapeutic perspectives of transcranial magnetic stimulation in dementia. Clinical Neurophysiology, 132(10), 2568-2607. https://doi.org/10.1016/j.clinph.2021.05.035
9. Lissemore, J. I., Wengle, L., Daskalakis, Z. J., & Blumberger, D. M. (2021). Insights into aging using transcranial magnetic stimulation. Factors Affecting Neurological Aging, 337-348. https://doi.org/10.1016/b978-0-12-817990-1.00030-5