Houston We Have a Problem
By the year 2050 the number of people over 60 is expected to reach 2 billion. Currently, 35.6 million people worldwide are living with dementia; by the year 2030, that number is expected to double to 75.6 million, making it a major public health concern. Mild cognitive impairment is an intermediate but debilitating stage on the spectrum from normal cognitive performance all the way to dementia. It is estimated that 60–65% of people with mild cognitive impairment will develop dementia during their lifetime. Slowing or halting this progression can have significant implications for quality of life and health care savings. If the progression to Alzheimer's disease (the most common form of dementia) could be delayed by only one year, total costs could be reduced by an estimated 113 billion American dollars by the year 2030.
Evidence suggests that physically active people have a significantly reduced risk of cognitive impairment and dementia. Across 16 studies which included 163,797 participants without dementia Hamer and Chida found that physically active participants showed a 28% reduction in risk of developing dementia and a 45% reduction in Alzheimer's disease. Anther study consiting of 89,205 adults over the age of 40 also found that higher levels of physical activity was associated with reduced risk of cognitive decline and dementia. Across another 15 studies found that physically active individuals reduced their risk of cognitive decline by 38%. Daviglus et al. and Beckett et al. also showed across 9 studies among older adults that physically active older adults reduced their risk of developing Alzheimer's disease, relative to their inactive counterparts.
Older adults without dementia can expect to have 1–2% decline of their memory centers per year, while individuals with Alzheimer's disease experience larger volume loss. Other studies have shown that increasing age is associated with lower serum and plasma levels of brain-derived neurotrophic factor (BDNF), a key growth factor involved in learning and memory. A meta-analysis by Dinoff et al. involving aerobic exercise and resistance training in 910 healthy adults of all ages revealed an overall increase in BDNF levels following exercise interventions. Neuroplasticity, the brain's ability to create and reorganize synaptic connections, appears to be an important mechanism for improved cognition with exercise among adults of all ages. A study conducted by Colcombe et al. using functional MRI revealed aerobically trained older adults demonstrated increased neural activity in the frontal and parietal regions of the brain compared to controls. Similarly, Voss et al.'s study revealed improvements in functional connectivity throughout the brain following 12 months of aerobic training in older adults. A cross-sectional study of 165 healthy older adults found that individuals with higher fitness levels had preserved brain volumes and better performance on a spatial memory task compared to those with low fitness levels.
There is no doubt that there is plenty of evidence out there validating the use of physical exercise on reducing the risk of cognitive impairment later in life. So if the literature is undeniabe, why is cognitive decline amongst the most common diseases effecting our nation? Through the next section of this article we will discuss the major known mechanisms contributing to cognitive impairment and then dive into what we can do to help combat those factors and improve cognitive performance.
What Causes Cognitive Impairment?
Studies of older adults and individuals with type 2 diabetes revealed that those with higher levels of inflammation had smaller regions of their memory centers in their brain compared to those with low levels of inflammation. A cross-sectional study of 3,298 older adults reported that higher inflammatory levels were associated with lower Mini-Mental State Examination scores. A longitudinal study of 3,031 healthy older adults found that those with the highest concentrations of inflammation had a 24% increased risk of developing cognitive impairment compared to individuals with low levels of inflammation. There is encouraging evidence from a recent systematic review of 13 studies that healthy sedentary adults of all ages who participate in aerobic exercise and resistance training can reduce inflammatory biomarkers. Stronger effects were found in older adults, with high-intensity aerobic exercise being the most effective in reducing inflammation. A study involving adults over 60 who participated in 16 weeks of aerobic, resistance, and neuromotor exercise (which includes balance, coordination, agility, gait, and proprioceptive training) demonstrated greater reductions in inflammatory markers and increases in peripheral BDNF in the exercise group than in the non-exercising group. Further analyses revealed that active individuals with mild cognitive impairment showed significant improvements in executive function and attention. Aerobic exercise releases anti-inflammatory substances mitigating the levels of inflammatory cytokines and ulimtatey leads to improved cognitive performance.
Cardiovascular and cerebrovascular disease risk factors such as hypertension, dyslipidemia, diabetes, and hyperinsulinemia increase the risk of cognitive impairment and dementia. An observational study followed 3,381 adults for 25 years and found that elevated blood pressure and higher fasting blood glucose increased the risk of cognitive impairment and dementia later in life. Elevated blood pressure decreases blood flow and metabolism to the brain and contribute to higher rates of cognitive impairment in elderly individuals. With all that being said is there anything we can do to reverese poor cardiovascular and cerebrovascular function and improve cogntive performance? Vidoni et al. determined that changes in fitness levels mediated cognitive improvements in older adults who participated in an aerobic exercise. Brown and colleagues found a significant association between physical fitness, cerebrovascular regulation, and cognitive function in a cross-sectional study of 42 healthy older women. A study of older adults revealed that 12 weeks of aerobic training resulted in higher resting blood flow to the brain and improved immediate and delayed memory scores compared to controls. Finally, higher fitness levels among female participants of all ages were associated with improved executive function and increased cerebral oxygenation in the frontal areas of the brain compared to women with low fitness levels. Exercise training is known to enhance oxygen and glucose transport to the brain, thereby increasing cognitive performance.
Indeed, there is longitudinal and cross-sectional evidence indicating that older adults with higher rates of chronic stress are 2.7 times more likely to develop Alzheimer's disease, and higher cortisol levels are associated with worsening cognition among older adults. In contrast, a longitudinal study of 52 older adults found that higher cortisol levels were associated with slower cognitive decline in those with mild cognitive impairment but not in those with normal cognition. A systematic review of 25 studies in individuals with and without chronic diseases revealed that yoga interventions improved measures of cortisol, heart rate, and blood pressure compared to controls. A meta-analytic review of 40 interventional studies found that Tai chi has positive effects on both anxiety and depression. A cross-sectional study of 42 middle-aged and older adults revealed that people who practiced Tai chi and yoga demonstrated significant improvements in mental health outcomes compared to those who performed aerobic exericise. Four meta-analyses have found beneficial effects of mind-body exercise on cognition among older adults. A study of 118 older adults participating in an 8-week yoga intervention, after which yoga participants demonstrated improved executive function and an attenuated cortisol response compared to those in the control group. Importantly, the change in self-reported anxiety and cortisol levels predicted performance on the executive function tasks, indicating that downgrading the HPA Axis response is a potential mechanism by which mind-body exercise improves cognition among older adults.
"The more you use your brain the more brain you will have to use." -George A. Dorse
So What Can We Do?
Resistance Training vs Aerobic Exercise
Colcombe and Kramer concluded in their meta-analysis of 18 randomized controlled trials in sedentary older adults that combined resistance training and aerobic exercise yielded greater positive effects on cognition compared to aerobic exericise alone and/or no exercise use. Similarly, Barha and colleagues discovered in their meta-analysis of healthy older adults that combined training benefitted global cognitive function and episodic memory more than aerobic exercise and resistance training alone. Many of the patients that make their way to Peak Brain Performance Centers are seeking relief after a head injury which makes the recommendation for what type of exercise to perform a little more intricate of a process. For example, if a patient is struggling with a vestibular disorder they probably aren't going to do so well with performing exercises that require a lot of bouncing (running) or changes in position (lying to standing/seated to standing). On the flip side if you are struggling wtih an autoimmune disease and stress is a big contributing factor to your current state of health we aren't going to be doing an exercise that you absolutley despise performing everyday. You're are exceptionally unique and as such your treatment interventions should be as well.
Exercise frequency also appears to be an important predictor of cognition. Northey et al. determined that when individuals exercised more frequently (5–7 sessions per week)
they faired better and saw greater benefits in cognitive performance than those that were less active (less than 4 session per week). This is also another factor that has to be taken on a case by case basis. Again going back to my personal bias based upon the patients that I treat, that being that most have head injuries. Often times individuals with head injuries can be exercise intolerant meaning that too much physical activity can flare their symptoms and so they have to incrementally work back up to what one would consider a normal workload. Also, being able to make a full recovery before beginning the next training session is something that should be taken into careful consideration. You're exceptionally unique and as such your treatment interventions should be as well.
Exercise intensity is also a significant predictor of cognitive benefit. In their meta-analysis of 36 studies, Northey et al. determined that high and moderate intensity exercise of all types were superior to low-intensity exercise in terms of cognition in older adults. Moreover, improvements in cognition have been obtained using low-intensity exercise, such as Tai chi and yoga. As such, it would be fair to say that exercise at any intensity may show positive improvements in ones cognition. Just like everything else the intensity that one performs said exercise should be determined on a case by case basis. If possible I always prefer my patients perform a high intensity exercise (difficult for you to hold a conversation while performing said exercise) but not everyone is capable of doing that and so we cater the plan to whatever suits them and their needs. Depending on the severity and whatever other comorbidities the patient has I typically take the stance of starting low and slow and if they are not seeing the intended outcomes or not experiencing any symptom flares we can always increase the intensity. You're exceptionally unique and as such your treatment interventions should be as well.
Longitudinal studies have reported that exercise session duration may be an important predictor of cognition among older adults. This is supported by evidence from the meta-analysis by Northey et al., who determined that sessions lasting 45 minutes or longer were more beneficial for cognitive performance than shorter sessions. A study conducted with four groups of older adults (controls, 50%, 100%, or 150% of the recommended dose of 150 minutes per week) who performed aerobic exercise of progressive intensities for 26 weeks revealed that a change in fitness mediated the effect of session duration on visuospatial performance. A dose response was apparent, with longer session durations enhancing improvements in visuospatial function. This can be a tricky one because the longer in duration that we exercise the more inflammatory cytokines we are releasing into circulation and so if the main contributory mechanism as to why you are experiencing some sort of cognitive impairment is inflammation we probably won't be doing long session. My typical recommendation consists of starting with 5 minutes of a high intensitiy exercise per day. Monitor how you feel throughout that day and if you feel good then up the duration the following day. You're exceptionally unique and as such your treatment interventions should be as well.
I hope you were able to learn something from this aricle and that you are now better equipped with tools to start your journey back to the Einstein you once were. I also hope that you see the complexity that is involved with creating a managment plan for an individual struggling with cognitive decline because while there are guidelines that we can try to mimic you are a unique indivual and cognitive decline is multifacted. If you or a loved one are struggling with cognitive decline utilize the concepts discussed in this article but also keep in mind that things in textbooks (or research articles in this case) don't always translate direclty to patient care. This is just data that should be used to help guide you (or your provider) in the right direction when it comes to managing cognitive impairment. Here we have discussed one possible tool, that being the use of exercise in the treatment of cognitive decline. If at first you don't succeed don't get discouraged because you are atleast now one step closer to your goal.
Quigley A, MacKay-Lyons M, Eskes G. Effects of Exercise on Cognitive Performance in Older Adults: A Narrative Review of the Evidence, Possible Biological Mechanisms, and Recommendations for Exercise Prescription. J Aging Res. 2020 May 14;2020:1407896. doi: 10.1155/2020/1407896. PMID: 32509348; PMCID: PMC7244966.