Of all the lifestyle
changes that have been studied, taking regular physical
exercise appears to be one of the best things that you can
do to reduce your risk of getting dementia.
Several studies
looking at the effect of aerobic exercise (exercise that
increases your heart rate) in middle-aged or older adults
have reported improvements in thinking and memory, and reduced
rates of dementia.
EXERCISING IN
MID-LIFE
Prospective
studies follow the health and behaviour of a group of people
over time. Several prospective studies have looked at middle-aged
people and the effects of physical exercise on their thinking
and memory in later life. Combining the results of 11 studies
shows that regular exercise can significantly reduce the
risk of developing dementia by about 30 per cent. For Alzheimer's
disease specifically, the risk was reduced by 45 per cent.
One particular
study looked at health behaviours of over 2,000 men in Wales,
and followed them for 35 years. Of the five behaviours that
were assessed (regular exercise, not smoking, moderate alcohol
intake, healthy body weight and healthy diet), exercise
had the greatest effect in terms of reducing dementia risk.
Overall, people who followed four or five of the above behaviours
were up to 60 per cent less likely to develop dementia.
In the short
term, aerobic exercise can also improve the performance
of healthy adults on thinking tests. Pulling together the
results of 29 clinical trials, a month or more of regular
aerobic exercise resulted in improvements in memory, attention
and processing speed when compared with regular non-aerobic
exercise such as stretching and toning.
EXERCISING IN
LATER LIFE
Although less
research has been done with healthy older people, there
is some evidence to show older people can also reduce their
risk of dementia with regular exercise. In a study of 716
people with an average age of 82 years, people who were
in the bottom 10 per cent in terms of amount of daily physical
activity were more than twice as likely to develop Alzheimer's
disease as those in the top 10 per cent.
A literature
review found 27 studies looking at the effect of physical
activity on brain function in people over 60 years of age.
In 26 of the studies there was a clear link between physical
activity levels and cognitive performance, suggesting that
exercise might be an effective way to reduce cognitive decline
in later life.
Aerobic exercise
has also been shown to affect the brains of healthy older
people. In a modest-sized controlled trial, one year of
aerobic exercise resulted in a small increase in the size
of the hippocampus (the key brain area involved in memory),
which was the equivalent of reversing one to two years of
age-related shrinkage. A study of 638 people in Scotland
that asked people about their activity levels found those
who were physically active at age 70 experienced less brain
shrinkage over three years than those who were not.
WHAT DOES PHYSICAL
ACTIVITY MEAN?
The research
studies in this area do not all use the same definition
of 'physical activity' or exercise. In general they are
referring to aerobic exercise performed for a sustained
period of time, perhaps 20–30 minutes. Most of the
studies report on the effects of aerobic exercise done several
times a week and maintained for at least a year.
However, physical
exercise does not just mean playing a sport or running.
It can also mean a daily activity such as brisk walking,
cleaning or gardening. One study found that the risk of
Alzheimer's disease can be reduced by daily physical tasks
such as cooking and washing up.
AREAS OF UNCERTAINTY
Usually, we
would like there to be randomized controlled trials (RCTs)
that show how one factor can influence another. To date,
no RCT has shown an exercise regime can prevent dementia,
although there are several in progress across Europe.
