A little food for thought
The average retirement age of a physician is between 67-74 years of age. Of those physicians who leave full time work, 40% will continue with some part time medical practice. The overall average life expectancy in the US is 79.3 yrs (F-81.6, M-76.9). That means life will end for 50% of all adults at that age … however 50% will continue to live, maybe for many more years. College graduates also tend to have a greater than 8 year life expectancy over their counterparts (making up a significant portion of the latter half on the Gaussian curve). There are things beyond our control that will impact our mental health and longevity including genetics, family history and acute medical illness. However, the odds are we will be around for a few more election cycles.
Abnormal brain aging
Dementia is defined as the loss of cognitive capacity to the detriment of social functioning and individual living that lasts longer than 6 months. Though memory loss is an early component of this disorder, other symptoms include executive functioning, language difficulties, working (immediate) memory, spatial memory and visual memory. The risk of someone getting dementia at age 65 is 1:70. This increases to 1:5 by age 85.
There are many causes of dementia, the most well-known being Alzheimer’s disease. Alzheimer’s and vascular dementia account for a large percentage of severe onset dementia.
Dementia and the normal aging brain
Dementia is not considered the normal process of brain aging. However, it is clear that the normal aging process also demonstrates progressive functional losses in perception, cognition and memory. A growing body of evidence seems to suggest a down-regulation of neuromodulatory system functions and increasingly poor signal–to-noise conditions (getting lost in the process). Traditional thought was that the machinery of thinking simply wore down (Mahnke et al , 2006). It has been shown that four core biological factors may contribute to normal brain aging.
- Reduced schedules of brain activity (going through the motion)
- Noisy processing (inability to filter),
- Weakened neuromodulatory control
- Negative learning (lack of input).
These combined components may produce “negative” brain plasticity and a decrease in function.
Teaching an old dog new tricks
The hippocampus and the parahippocampal area, a key memory region, has been shown to decrease in size with age (a normal occurrence)(Raz et al 1998). White matter changes have also been seen on MRI studies with increasing memory loss (Madden et al 2009). Despite these normal physical changes, the brain has the ability to alter its functional capacity throughout life both in a negative and positive manner. For example, the same group of patients who demonstrated an age related decrease in size of the hippocampus actually showed a subsequent increase in size with simple exercise for 6 months (AARP Bulletin, 2016). There are numerous stories of patients with traumatic brain injuries leading to impairment of motor function (Doidge “the Brain that changes itself”, 2003). Over time, these patients were able to regain function by diverting the brain activity to another area of the gray matter.
The idea of improving brain function by taking advantage of this unique ability of the brain to “respond ” has created much interest in an attempt to provide tools to counter the normal aging brain and prevent the onset of dementia. We will discuss several of these recommendations in later sections.
“…Can’t Remember…” What is really going on?
Several studies have shown consistent areas of decreased function with normal brain aging. Of these, a decrease in speed of the cognitive process was the most consistent change in the aging brain (Birren 1965, Woods 1980, Cerella 1985, Salthouse 1996). This was related to an increase in the deletion of random links in the memory network creating a much longer memorial processing pathway (Craik 1982, Rabinowitz 1982).
Deficiencies in two important mechanisms were outlined :
- “Limited time mechanism” in which the older adult has a more difficult time performing higher-level operations within an allotted time.
- “Simultaneity mechanism” – decreased ability to consider concurrent task-relevant components because of the loss of earlier processing pathways (Salthouse et al 1996). Interestingly this correlated with findings that suggested the difficulty of the aging brain to filter irrelevant material, subsequently interfering with the primary task. Again speed of processing was the most age-related variance in cognitive tasking (salthouse 1985a, 1985b, 1996). However, the task was eventually accomplished in this group if time demands were eliminated. It is easy to understand how important these capacities are to the ability of the physician to provide patient care, especially in complex or urgent situations.
Is it a one way street?
As the process of cognitive aging has been better understood, it is predictable that the question of reversibility and maintenance would be explored. With the assistance of environmental support (contextual guidance, mental crutches), memory was found to be improved with trigger words or phrases (vitally important in the case of my ever-changing CHOA password) (Craik 1986, 1987, Smith 1977). Familiarity of the situation or the physical surroundings was also critical to minimizing age deficits (Craik 1994, Park 2000).
Numerous studies have shown the effectiveness of structured mental training programs in which prolonged cognitive exercises over 6 months demonstrated significant improvement in function (…Could this be (gulp) the argument for recertification?) (Mahncke 2006,Shaffer 2016, Mahncke Connor 2006). The hypothesis is that the use of structured brain exercises in an aging population can be utilized to create positive brain plasticity and potentially prevent or delay the need for expensive assisted living needs.
Specific repetitive functions (albeit with constant changing parameters .. think patient care) within a daily activity can also elicit positive physical changes in the brain. For example, London cab drivers had larger hippocampi than London bus drivers because of the need of the former to constantly assimilate new information and create complex spatial information to navigate routes (Maguire 2006). Bus drivers obviously took repetitive routes. Bilinguals were also noted to have changes in the brain compared to monolinguals, specifically an increase in the left inferior parietal cortex (Mechelli et al 2004). Professional musicians also demonstrated a significant increase in gray matter over non-musicians (Gaser et al 2003). Even studying for exams produced changes in the parietal cortex of medical students before and after a test (Draganski 2006).
Maybe even more relevant than compensation of brain function is the idea of maintaining cognitive health. It is clear that there are certain activities that have been shown to decrease the chance of dementia and maintain a high level of cognitive function. Four recurrent areas of discussion include:
- Mental stimulation
- Physical exercise
- Control chronic health issues