"Doing moderate exercise several times a week is the best way to keep the mind sharp if you're over 50," BBC News reports.
A review of existing data found both aerobic exercise and strength training appeared to improve cognitive functions, such as memory, attention, and how well people carry out tasks.
The review brought together information from 39 studies in the biggest summary of the effects of exercise on mental ability to date.
Previous summaries of research have had unclear results. But this study found most types of moderate to vigorous exercise had a positive effect as long as sessions lasted at least 45 minutes.
The researchers say doctors should recommend people take part in exercise on as many days a week as possible.
Importantly, the study found people benefited even if they were already showing signs of mental decline. This means exercise might help those with early signs of dementia stay mentally alert for longer.
The study provides yet another reason to keep active in later life – both the mind and the body should benefit.
It's recommended that adults do at least 150 minutes of exercise a week, ideally through a combination of aerobic and strength training exercises.
Where did the story come from?
The study was carried out by researchers from the University of Canberra and Australian National University, both in Australia. No funding information was provided.
The study was widely reported, with somewhat conflicting and inaccurate advice in the headlines.
The Daily Telegraph and the Daily Express say people only need exercise for 45 minutes a week, although most of the studies included exercise programmes twice a week or more.
The Sun says "walking benefits the brain more than cycling" – but the study didn't present any evidence for this.
The intensity rather than the type of exercise was important, so moderate-intensity cycling should be as good as moderate-intensity walking or running.
What kind of research was this?
A meta-analysis of RCTs is a good way to summarise and pool evidence to show whether a particular intervention (in this case, exercise) affects a particular outcome (in this case, cognitive function).
What did the research involve?
Researchers looked for any RCTs that compared an exercise programme with a control group, among adults over 50 living at home, with at least one test of cognitive function (mental ability) as an outcome.
They excluded studies where exercise was not the only intervention – for example, exercise plus brain training – to focus the study on exercise alone.
They then pooled the results between exercise groups and control groups to find the standard mean difference from baseline cognitive function.
Researchers also analysed the results by:
- type of exercise (aerobic, resistance/strength training, a combination of the two, yoga and tai chi)
- intensity (low, moderate or high)
- duration of exercise session (less than 45 minutes, 45 minutes to an hour, more than an hour)
- length of programme (4-12 weeks, 13-26 weeks, more than 26 weeks)
- frequency of exercise sessions (two or fewer, 3 or 4, 5-7)
Tests of cognitive function included overall cognition, attention (such as ability to process information quickly), executive function, long-term memory, and short-term working memory.
All the studies were assessed for risk of biases, such as publication bias. The researchers did not exclude any studies based on the date of publication or type of exercise.
What were the basic results?
The study found, overall, taking part in an exercise programme had a small to moderate positive effect on cognitive function, although this varied considerably from one study to another.
People's mental abilities at the start of the study made no difference to the results – people were likely to benefit even if they already showed signs of mild cognitive decline.
Looking at the different types of exercise separately, the authors found:
- all types of exercise studied except yoga showed a positive effect on cognitive function
- aerobic and resistance training (such as weight training) showed similar effects, suggesting that both types of exercise are important
- studies where exercise duration was 45 minutes to an hour showed better results than shorter or longer exercise sessions
- all lengths of exercise programme, and programmes with all frequencies of sessions, had a positive effect – there were no clear differences between them
- moderate and vigorous exercise showed better results than low-intensity exercise
The type of control group made a difference. Where people in the control group had either no intervention or a sedentary intervention (such as attending lectures or a computer course) the difference in cognitive function compared with exercise was notable.
However, when the control group did stretching exercises or attended social events, the difference was small enough that it could have been down to chance – in other words, it wasn't statistically significant.
The quality of the evidence was assessed as "moderate" overall. It's not possible to blind people in exercise studies as to whether or not they're doing exercise, which means the studies all have a risk of bias from people knowing whether or not they're being treated.
How did the researchers interpret the results?
The researchers say their findings "suggest that an exercise programme with components of both aerobic and resistance-type training, of at least moderate intensity and at least 45 minutes per session, on as many days of the week as possible, is beneficial to cognitive function in adults aged more than 50 years".
They say future studies should accept as a starting point that exercise is beneficial, and concentrate on ways to "refine the prescription" to identify the best exercise programme to benefit brain function.
It's no surprise to hear that exercise has health benefits – but not everyone knows that it's good for your brain as well as your body.
This study provides evidence that, even for people with some signs of declining mental function, regular moderately intense exercise has a positive effect.
There are a few minor caveats, however. Although the study showed tai chi is beneficial, this was based on only four trials.
And it's not completely clear how often people need to exercise. The study found any number of weekly sessions showed a benefit, but it's reasonable to think more sessions would be more beneficial.
The reasons why physical exercise benefits mental function are thought to include better blood flow to the brain, which keeps nerve cells healthy and supplied with oxygen, lower inflammation and less cellular damage.
Current guidelines for exercise for adults in the UK are to do at least one of the following:
- 150 minutes of moderate aerobic activity, such as cycling or fast walking, every week, and strength exercises on two or more days a week that work all the major muscles (legs, hips, back, abdomen, chest, shoulders and arms)
- 75 minutes of vigorous aerobic activity, such as running or a game of singles tennis, every week, and strength exercises on two or more days a week
- a mix of moderate and vigorous aerobic activity every week (two 30-minute runs plus 30 minutes of fast walking equates to 150 minutes of moderate aerobic activity) and strength exercises on two or more days a week
Other ways you can reduce your risk of dementia include: