In a new review paper, scientists show that exercise can alleviate age-related cognitive decline, but not all types of exercise are created equal [1].
Watch your head
Lifestyle choices, such as exercise and diet, are the most powerful anti-aging interventions currently available to us, and they might be the only effective ones. Exercise, in particular, has been proven to slow down various age-related changes [2].
One of these changes is cognitive decline. It spares virtually no one, and in some people, it grows into devastating dementias, such as the deadly Alzheimer’s disease. Geroscientists suspect that the reason not all old people become demented is that most die of other causes before age-related dementias can get to them. As life expectancy continues to rise, finding ways to maintain cognitive health becomes extremely important.
Numerous studies have tested the effect of exercise on age-related cognitive decline, mostly with positive results, but there are many confounding variables, such as types of exercise, sex, and BMI (body mass index). In this new review, which encompasses 44 studies with almost 5000 participants, the authors set out to determine the minimum and optimal amounts of various types of exercise for influencing age-related cognitive decline.
Some exercise is better than nothing
The researchers begin with a brief overview of the current literature, noting that most of it still focuses on aerobic exercise, while other types of exercise have been shown to confer cognitive benefits as well – such as resistance training, dancing, and mind-body practices [3].
In their analysis, the scientists compare various types of exercise using their MET (metabolic equivalent), an established metric of energy expenditure. One MET-minute equals the amount of energy our body consumes during one minute of absolute rest. Brisk walking and vigorous weight training score at 5 MET, bicycling on flat terrain is equivalent to 9 MET, and running is one of the most energy-consuming activities at 11.5 MET. That means one minute of running uses up to 11.5 MET-mins worth of energy.
When measuring only MET equivalents and not type of exercise, the review shows that there is no minimum amount of exercise below which it does not promote cognition, however slightly. This sits well with the saying (officially endorsed the WHO) that some exercise is better than no exercise. However, according to the review, the difference is only perceptible at around 700 MET-minutes per week, which is on the smaller side of WHO recommendations (600-1200 MET-minutes per week).
Starting from 1200 MET-minutes per week, however, the effect becomes weaker, although it never plateaus, which led the researchers to conclude that beyond this point, the further benefits of exercise are unproven. This result aligns well with previous research showing that the benefits of exercise might peak at some point and even be reversed by too much exercise.
Obesity erases the effect
The differences between various types of exercise were quite significant. Resistance exercise shows a powerful effect, but it peaks at around 400 MET-minutes per week and then rapidly declines as the dose gets higher, producing an inverted U-shape on the chart. Walking and weightlifting had less pronounced effects on cognition than aerobic exercises. A mix of various aerobic exercises yielded good results, but a balanced combination of resistance training, weightlifting, and other exercise may be better. One previous meta-analysis indeed found that a mix of various types of exercise is most beneficial [4].
Finally, obesity seems to drastically change the picture. In people who are overweight, exercise improves cognition only slightly up to about 600 MET-minutes, and any further addition of MET-minutes diminishes the effect. Not only is obesity a major driver of aging, it can dampen the effect of exercise.
The researchers add the obvious observation, which can be taken as a warning, that it might be hard for aging people who had previously led sedentary lifestyles to drastically ramp up their exercise capacity to the recommended levels.
Conclusion
This review provides important insights into the effect that exercise can have on age-related cognitive decline, showing us that not all types of exercise are the same, and answering the question of how much exercise someone actually needs to start improving cognition in old age. It also reminds us that exercise is one of the few interventions available today that can put a dent in aging.
Literature
[1] Gallardo-Gómez, D., del Pozo-Cruz, J., Noetel, M., Álvarez-Barbosa, F., Alfonso-Rosa, R. M., & del Pozo Cruz, B. (2022). Optimal Dose and Type of Exercise to Improve Cognitive Function in Older Adults: A Systematic Review and Bayesian Model-Based Network Meta-Analysis of RCTs. Ageing Research Reviews, 101591.
[2] Shephard, R. J., & Shek, P. N. (1995). Exercise, aging and immune function. International journal of sports medicine, 16(01), 1-6.
[3] Biazus-Sehn, L. F., Schuch, F. B., Firth, J., & de Souza Stigger, F. (2020). Effects of physical exercise on cognitive function of older adults with mild cognitive impairment: A systematic review and meta-analysis. Archives of Gerontology and Geriatrics, 89, 104048.
[4] Huang, X., Zhao, X., Li, B., Cai, Y., Zhang, S., Wan, Q., & Yu, F. (2021). Comparative efficacy of various exercise interventions on cognitive function in patients with mild cognitive impairment or dementia: a systematic review and network meta-analysis. Journal of Sport and Health Science.
