Good observation that:
1). “However, it has a major weakness; it does not explain why some individuals at the latest stages of their development do not have decline cognitive abilities.” and
2) “Research shows that not all individuals who enter the elderly population age bracket develop mental health disorders. The model does not provide an adequate explanation of the difference.”
These are related to your original comment, “This leads to the reduction of the processing speed and the decline in the sensory capacity. As a result, the individual becomes prone to mental health problems.” for two main reasons
The first reason that there are at least two different forms of aging, healthy and unhealthy. If a person is healthy, we expect to see some cognitive decline, but nothing catastrophic or sudden. In healthy older adults, we see good cognitive processing and colloquially people say that an older person is “still sharp”. We see this in Supreme Court justices – still going strong in many important ways.
The second type of aging is unhealthy or even pathological. Unhealthy aging and pathological aging are similar concepts but unhealthy can just be due to unfortunate lifestyle choices whereas pathological aging may reflect a genetic or acquired disease process. In both cases, a person’s brain and body deteriorate in ways that we don’t see in healthy people so their cognition is affected by normal change over time plus the additional effects of poor health and perhaps even a pathology on top of both of those. Think of this last example as a “triple threat”. For a specific example, consider the aging of someone who is both an alcoholic and has a separate degenerative brain disorder like Parkinson’s disease. For someone in this situation, time, plus alcohol, plus the Parkinson’s disease all extract a toll on their brain, body, mind, lifestyle, social circles, and their psychology.
So the reason that many older people retain a high degree of their cognitive abilities and even a good amount of physical mobility is related to what sources of damage they face. If they only face time, and all of the rest of their life and body is “healthy” we see “normal” or “healthy'” aging.
However, if they are afflicted with diseases, mental disorders, bad habits, injury, assault, poor nutrition, lack of exercise, etc. those compound the damage to the brain and body, resulting in what can be shockingly swift and severe declines in cognition. Strokes (large or small) can do this and many people with dementia have dementia due to having many very small strokes and the resultant loss of brain tissue.
For a really excellent explanation of the different paths of healthy vs. unhealthy aging, check out the Harvard Study of Adult Development and news about it like this: https://news.harvard.edu/gazette/story/2017/04/over-nearly-80-years-harvard-study-has-been-showing-how-to-live-a-healthy-and-happy-life/ (Links to an external site.)Links to an external site.
and the more important article http://www.asaging.org/blog/aging-well-thoughts-75-year-old-study (Links to an external site.)Links to an external site.
This latter one starts off by listing three genetic problems as being the top reasons for unhealthy aging (alcoholism, major depression, and dementia) so it is interesting to consider how much and when the unfolding of people’s genetics determines their later life cognitive health and capacity.
Please let me know your thoughts about the ideas above.
You also make the good observation “To fill the gap in the effort to explain the decline in cognitive abilities in some but not all individuals, the model should be modified in such a way that it specifies those individuals who have lower chances of developing mental health problems due to decline in cognitive abilities.”
For a challenge, what recent research on aging identifies those older adults who are most at risk for developing mental health problems due to cognitive decline? We probably don’t want to include Alzheimer’s disease in this topic because that is a brain disorder which affects both cognition and mental health while people also fear their cognitive decline – a double problem. Here is one example https://www.researchgate.net/profile/Mikko_Laakso/publication/11914576_Midlife_vascular_risk_factors_and_late-life_mild_cognitive_impairment_A_population-based_study/links/5a4b343da6fdcce1972178ce/Midlife-vascular-risk-factors-and-late-life-mild-cognitive-impairment-A-population-based-study.pdf (Links to an external site.)Links to an external site. and I found it with a google search for, “risk factors for cognitive decline and mental disorders”.
