A recent editorial in JAMA Neurology (1) suggested that there may be a general decline in Dementia risk in the future because of better brain health due to worldwide improvements in the standard of living, education, and prevention and treatment of serious diseases. This provocative speculation contradicts the more common and dire predictions of a significant increase in Dementia as the world’s population ages. In this article, we explore the latest ideas about normal aging and cognitive decline with an eye on the future.
Most older people remember many ordinary things, like how to sing a familiar song and tie a shoe. Many people currently live into their 90s and beyond without any significant signs of cognitive impairment. It may take them longer to recall a word or a name, but their general language ability, vocabulary, and reasoning capacity can remain relatively intact.
What does tend to decline in normal aging is mental flexibility. Reliable recollection of facts, events, and practical knowledge becomes more complex, and it may become challenging to use newly learned information. Multitasking and executive functioning that requires speed, verbal, and mathematical reasoning typically slow down, especially after age 70.
In his book “Why We Remember” (2), Charan Ranganath suggests that we think of memory like a desk cluttered with crumpled-up scraps of paper. If you think about urgently rooting around on that messy desk, trying to find something important that you’ve scribbled on one of those crumpled scraps, you may begin to feel what it’s like to lose access to your memory.
Mild Cognitive Impairment (MCI) occurs when there is more difficulty with memory and thinking than expected at a person’s age. Although a person with MCI can still be independent, they may struggle with ordinary tasks and may feel easily frustrated, disorganized, and overwhelmed.
In a 2014 study (3) of people whose average age was 70, about 30 percent of people who had been diagnosed with MCI later developed Dementia. Dementia involves a further decline in memory and thinking skills, most commonly due to damage to the brain from a variety of causes. A specific disease-modifying drug for Dementia is not currently available, but some symptoms and underlying causes can be treated.
Mild Dementia is characterized by increased confusion, and reading and writing can become difficult or impossible. Repetitive or inappropriate questions and inaccurate answers can make conversation challenging, and it is not unusual for people living with Dementia to become disoriented, leave a safe place, and get lost. There is likely to be impulsive behavior, a diminished capacity for empathy, and, eventually, difficulty recognizing family and friends. At its most severe, a person with Dementia may become utterly dependent on others to manage their basic activities of daily living.
A definitive diagnosis of Dementia is complicated because the clinical evidence (seen by a doctor in their office or experienced by loved ones at home) of Dementia is very varied. That said, Alzheimer's disease (AD) pathology, specifically, is defined by physical damage to the brain tissue: clumps of proteins in the brain in the form of beta-amyloid plaques and neurofibrillary tangles. There is a highly accurate commercially available blood test (4) that detects these proteins, and there are two drugs approved by Medicare (lecanemab and donanemab) that dissolve some of the beta-amyloid plaque. Still, they have relatively modest benefits and will not reverse a person’s memory loss or provide lasting improvements. Lecanemab, for example, is said to delay the progression of AD by about five months (5). These drugs require an extensive commitment of time and money, and they have a high risk of serious side effects. Drug regulators in several countries have declined to approve the drugs out of concern that the risks outweigh the modest benefits, and several major US healthcare institutions have opted not to give the drug to anyone with a problematic genetic profile (6).
As part of the search to identify cognitive impairment at the earliest possible point so that effective treatments can be developed to prevent and delay the development of Dementia, the concept of Subjective Cognitive Decline (SCD) has recently appeared in the cognitive continuum (7). It is derived from the requirement by Medicare that the physician ask a patient over 65, at their annual wellness visit, whether they’ve been having any issues with their memory. Participants 60 years and older with normal cognition who participated in the large Framingham Heart Study were asked slightly different variations of that single question, “Do you feel your memory is becoming worse?”
Study participants were followed for up to 12 years. If they had answered “Yes,” indicating SCD, it was found that, over time, they had an increased risk of developing cognitive decline and all-cause dementia. On average, SCD preceded the development of MCI by 4.4 years, AD by 6.8 years, and all-cause Dementia by 6.9 years. This supported the premise that SCD could be an early or pre-symptomatic manifestation of impending neurodegeneration, and early detection is believed to improve the potential for treatment and prevention of further decline.
While research continues to focus on diagnosis, treatments, and cures, considerable emphasis has shifted toward studying lifestyle and environmental modifications that can reduce the risk and delay the development of cognitive decline. Investing in preventative health (8,9), like being fitted for hearing aids, has been shown to reduce brain damage due to normal biological aging (10). A 2024 article (11) estimates that “…nearly 50 percent of all Dementia cases are preventable…” Experts agree that along with physical exercise or staying socially active, engaging in cognitively stimulating activities or hobbies can help protect against cognitive decline by building mental muscle or “cognitive reserve” (12,13). And these activities have virtually no downsides!
Some healthy lifestyle and environmental modifications that have been scientifically validated to reduce the risk of cognitive decline are listed below and discussed here (14).
Eat healthily, the so-called MIND diet.
Find a way to exercise regularly to whatever degree is possible for you. Breaking a sweat builds your brain.
If you aren’t working or socially active, consider volunteering or getting involved somewhere to be socially and intellectually stimulated.
Try to get the best medical care possible if something seems to be physically or psychologically wrong. Ask your doctor to adjust medications that affect cognition.
Correct even mild hearing or vision loss; reduced activity in the brain due to age-related sensory changes can lead to faster rates of atrophy and an increased risk of cognitive decline and dementia (15).
Address sleep problems: untreated, they may contribute to cognitive decline and affect the brain's resilience (16).
Moderate or eliminate alcohol consumption and stop using tobacco products.
Minimize stress.
Widespread prioritizing of healthy habits will have a measurable impact on the future incidence of cognitive decline. Perhaps, hopefully, our grandchildren will learn whether improved brain health, supplemented by the development of targeted treatments and cures, will result in a decrease in the future risk of cognitive decline.
Contributing Author: Carol A. Butler, Ph.D.
Authors' opinions are not necessarily those of the Dementia Society, Inc. We do not endorse nor guarantee products, comments, suggestions, links, or other forms of the content contained within blog posts that have been provided to us with permission, paid or otherwise. Dementia Society does not provide medical advice. Please consult your doctor. www.DementiaSociety.org
References
Vemuri, P. 2024. Improving trends in brain health explain declining dementia risk? JAMA Neurology, 81(5):442-443. Published online March 25, 2024.
Ranganath, C. 2024. Why We Remember. Doubleday, New York.
Roberts RO et al. 2014. Higher risk of progression to dementia in mild cognitive impairment cases who revert to normal. Neurology Jan 28; 82(4): 317-325.
Palmqvist, S. et al. 2024. Blood biomarkers to detect Alzheimer disease in primary care and secondary care. Jama, 332(15):1245-1257.
van Dyck CH et al. 2023. Lecanemab in early Alzheimer’s disease. NEJM, 388:9-21.
Bogdanich, W. and Kessler, C. What Drugmakers Did Not Tell Volunteers in Alzheimer’s Trials. New York Times October 23, 2024.
Kang, M. et al. 2024. Subjective cognitive decline and longitudinal assessment and risk for cognitive impairment. JAMA Psychiatry, published online July 3, 2024.Van Dyck, C. et al. 2022.
Taquet, M. et al. 2024. The recombinant shingles vaccine is associated with lower risk of dementia. Nature Medicine.30, 2777-2781. https://rdcu.be/dXxnR
Veronese, N. et al. 2022. Influenza vaccination reduces dementia risk, a systematic review and meta-analysis. Ageing Research Reviews, 73. https://doi.org/10.1016/j.arr.2021.101534
Marinelli J. et al. 2022. Association between hearing loss and development of dementia using formal behavioural audiometric testing within the Mayo Clinic Study of Aging (MCSA): a prospective population-based study. The Lancet Healthy Longevity. 3(12): E817-824.
Livingston G et al. Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. The Lancet Commissions 404 (10452): 572-628.
Krivanek TJ et al. 2021. Promoting Successful Cognitive Aging: A Ten-Year Update. J Alzheimers Disease June 1; 81(3): 871-920.
Blumen, H. et al. 2024. Cognitive reserve proxies are associated with age-related cognitive decline- not age-related gait speed decline. Neurobiology of Aging. 141:46-54.
Butler, C. 2024. Lifestyle modifications for brain health. https:www.dementiasociety.org/post/lifestyle-modifications-for-brain-health
Smith, D. 2024. How hearing and vision loss increase the risk of dementia. https://www.nytimes.com/2024/08/08/well/mind/hearing-vision-dementia-risk.html
Ho, P. et al.2024. Sleep, 24-hour activity rhythms, and subsequent amyloid-B pathology. JAMA Neurology, 81(8): 824-834.
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