Midlife Exercise Strengthens Cognition

Pam Harrison

April 24, 2017

Physical exercise that includes aerobic exercise or strength training of moderate intensity and lasts at least 45 minutes improves cognitive function in adults older than 50 years regardless of baseline cognitive status, a systematic review of randomized controlled trials shows.

"The study provides evidence to tell adults over the age of 50 that they should try to engage in physical exercise which includes components of aerobic and resistance training," Joseph Northey, PhD candidate, University of Canberra Research Institute for Sport and Exercise, Australia, told Medscape Medical News.

"Considering that there was also a trend towards this effect increasing as training frequency was greater, our findings are very consistent with exercise recommendations for this age group regarding overall health," he added.

The study was published online April 24 in the British Journal of Sports Medicine.

All Exercise Is Good Exercise

A total of 39 randomized controlled trials were included in the systematic review. The trials evaluated a variety of exercise interventions, all of which targeted community-dwelling adults older than 50 years. The main aim of all interventions was to assess the impact of those interventions on cognitive function.

"The mode of exercise was classified as aerobic, resistance training, multicomponent training (an intervention with both aerobic and resistance training components), tai chi or yoga," the authors write. Exercise intensity was rated as low, moderate, or high.

The researchers used a multilevel model to estimate an overall effect size of the various interventions on cognitive function relative to control groups. They also analyzed the impact of physical activity on global cognition, attention, executive function, memory, and working memory.

"Analysis of 333 dependent effect sizes from 36 studies showed that physical exercise improved cognitive function," the researchers report (P < .01), at a standardized mean difference of 0.29 compared with control persons.

Except for yoga, the researchers also found that all types of exercise produced significant and positive effects on cognition (P < .01).

However, when exercise training variables were taken into account, they found that interventions that lasted a minimum of 45 minutes and were of moderate to vigorous intensity had beneficial effects on cognition regardless of frequency.

"The effect of exercise on cognition was [also] statistically significant for all domains, except global cognition," they add. In particular, they found that aerobic exercise significantly enhanced cognitive abilities and that resistance training enhanced executive function, memory, and working memory.

The researchers note that this does not necessarily mean that resistance training is superior to other types of exercise, only that it appears to have particularly pronounced effects on these three domains of cognitive function.

Their analysis also determined that tai chi, a popular form of exercise among older adults, especially older Asians, also improved cognitive function.

They researchers note "this is an important finding because non-traditional modes of exercise, such as tai chi, may be suitable for less functional populations."

"The findings suggest that an exercise programme with components of both aerobic and resistance-type training, of at least moderate intensity and at least 45 min per session, on as many days of the week as possible, is beneficial to cognitive function in adults aged >50 years," they write.

Asked how physicians might encourage patients to exercise more, Northey pointed out that although physicians often emphasize the health benefits of being physically active, "we often forget that physical activity can and should be fun as well as sociable," he said.

"So physicians should try to encourage patients to find activities that they enjoy, maybe a sport that they did when they were younger, for instance, or that they meet up with a more active friend who can act as a mentor and a motivator."

Intensity Matters

Commenting on the findings for Medscape Medical News, Teresa Liu-Ambrose, PhD, PT, associate professor of physical therapy, University of British Columbia in Vancouver, said the review supports the idea that to benefit cognition, people need to engage in activities of at least moderate intensity.

"More needs to be determined, but there is evidence that intensity matters, and other reports have shown us the benefits of moderate-intensity exercise as well, so this review aligns to what we know," she said.

Dr Liu-Ambrose also pointed out that just because the practice of tai chi looks physically undemanding, it is not.

"There is a lot of learning involved with tai chi and a lot of finesses with the moments themselves if you want to do it well, so that imposes a sort of cognitive loading that we many not fully appreciate," she explained.

Tai chi also requires practitioners to recruit a fair amount of muscle strength, especially in the lower body, so that they can move in a fluid way, she added.

"In the past, we were so focused on aerobic training for cognitive health, and there's a lot of good evidence that it does benefit cognition, but if we want to promote exercise as a way to prevent cognitive decline with age, offering people a variety of activities that will allow them to enjoy the activity and sustain doing it over the long term is a nice message as well," said Dr Liu-Ambrose.

Dr Northey and Dr Liu-Ambrose have disclosed no relevant financial relationships.

Br J Sports Med. Published online April 24, 2017. Full text

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