If you’re 40 or more years old and your tolerance for those of us who drone on about exercise being the elixir of good health is approaching zero, new research suggests it might be time to consider a reset.
A July 2022 study, published in the Journal of the American Medical Association, by Canadian researcher Stephanie Chevalier, a scientist in the Metabolic Disorders and Complications Program at McGill University in Montreal, has concluded that, “With this study, we show for the first time that the presence of low muscle mass is significantly associated with faster cognitive decline and that this association is independent of muscle strength and physical activity level, among other factors.”
Why is this important? Research to date confirms that once cognitive decline associated with age sets in, we cannot reverse it. The McGill study offers hope that through our own actions, we can at least postpone or prevent age-associated cognitive decline. Muscle mass is a “modifiable factor” states the report, explaining that through resistance exercise (working muscles against resistance to increase their strength and size), and a diet with sufficient protein, we can significantly reduce muscle mass loss as we age.
Chevalier says, “Our results show that measuring low muscle mass may help to identify people who have greater risk of cognitive decline. We should measure muscle mass more widely.” Her implication is that by identifying low muscle mass as a biomarker of potential high-risk in patients, steps including additional exercise and resistance training might reduce their cognitive decline.
That’s great news, but she had me at “low muscle mass is significantly associated with faster cognitive decline.” I don’t think I’ll wait for our over-burdened health care system to measure or test me before realizing that maintaining muscle mass is a good thing.
Cognitive decline for most of us is inevitable. The American Academy of Neurology reports 8 percent of 65 to 69 year olds, 15 percent of those in their 70s, and 25 percent of 80 to 85 year olds experience mild cognitive impairment. The Centre for Disease Control and Prevention also confirms 12 percent of those 65 and older report frequent memory loss and confusion. Any proven opportunity to delay the onset of cognitive decline by a few years must be considered significant.
The exact order may differ, but polls and studies consistently rate the following as the biggest fears of seniors today: loss of independence, loss of memory, loneliness, declining health, inability to live at home and loss of dignity. Every one of these, plus our physical health, can be impacted by loss of executive function, our ability to organize our thoughts, concentrate, and make decisions.
To remain independent, whether living at home or in a residence, we need to be able to manage the tasks of everyday living with confidence. Safety and security, financial decisions, driving a vehicle, and relationships all demand clear thinking. Fighting loneliness demands that we be involved with others and our community. We need to be interested and engaged to do so. Although our overall health can be impacted by many things, this study is the first to prove a link between low muscle mass and mental health.
A 2012 study by Jeremy D. Walston, of John Hopkins School of Medicine, titled “Sarcopenia in older adults,” exemplifies how the loss of muscle mass has been viewed historically by medical researchers.
Since muscle accounts for approximately 60 percent of our body mass, and is a metabolically active organ, such a loss is bound to have major physiological effects
Sarcopenia is the involuntary loss of skeletal muscle as we age. Muscle loss begins in our 40s, and we experience a reduction of muscle mass of up to 50 percent by our 80s. Since muscle accounts for approximately 60 percent of our body mass, and is a metabolically active organ, such a loss is bound to have major physiological effects. Sarcopenia can be severe in older adults, and has been linked to physical disabilities, acute and chronic disease, insulin resistance, and rheumatoid arthritis, especially in women, yet there was no mention of cognitive decline also being related to sarcopenia.
Until this McGill study was released in July, there was little work on the relationship between muscle mass and cognitive decline, including the fact that low muscle mass may be predictive of accelerated cognitive decline in older adults.
The sample size and data quality used in the McGill study are important to its validity. Researchers tapped into a massive quantity of data provided by an ongoing Canadian Longitudinal Study on Aging, conducted by 160 researchers from 26 Canadian universities. The study began in 2009 and will follow more than 30,000 Canadians aged 45 to 65 until 2033, or their death, with the intention of discovering ways to help people live long and well.
The McGill study followed 8279 of the participants, half men and half women, average age 72, and measured their Appendicular (leg and arm) Lean Soft Tissue Mass (ALM) to establish a baseline. Twenty percent (1605) of those tested were found to have what is considered low ALM. The exact numerical definition of low ALM is still a moving target for researchers, so the McGill study used a specific percentage below the age-related muscle mass average to define low ALM in their study.
Cognitive testing of all 8279 participants three years later showed that the 1605 who displayed low ALM in the initial baseline tests were, “associated with faster three-year cognitive decline in executive functions and psychomotor speed.” Psychomotor speed is the ability to actively maintain and manipulate information quickly and allocate attentional resources among competing subtasks. It should be noted that ALM was not associated with memory loss.
Understanding exactly why this relationship between lower muscle mass and accelerated cognitive decline exists is limited, and is the subject of further research.
It is known that brain activity demands a huge amount of energy from our bodies. A fascinating 2017 study by a Cambridge University research group tested 62 male rowers to determine if their bodies favoured brawn (muscles) or brains. The rowers performed a three-minute mental recall test while at rest, then did a similar test while rowing full tilt. During the rowing test, mental recall dropped by 9.7 percent while power fell by 12.6 percent, yielding a drop in physical power nearly 30 percent greater than the drop in cognitive function.
Muscles are part of the body’s endocrine system, a messenger which directs the release of proteins called myokines and hormones into our circulatory system and how they are to be distributed to various organs, including the brain. The Cambridge study showed our brain prioritizes protecting executive function over muscle strength. The rower’s bodies literally stole energy from their muscles to feed their brains.
As muscle mass declines with age, we are less able to engage in physical activity and cardiorespiratory fitness wanes, hence there will be less blood flow to the brain and less energy available to be utilized for protecting cognitive functions. Less muscle mass also means that less myokines, which are released from muscles during contraction, will be produced. Myokines have anti-inflammatory benefits which support brain health and cognitive function.
Regardless of whether we have discovered the exact reasons why low muscle mass results in accelerated cognitive decline or not, the relationship is now clear. Thanks to this new study, I’ve got one more reason to head to the basement and my weight set — with fingers crossed it isn’t already too late.