FREEDOM AND SAFETY
One brisk walk a week could cut an older woman's risk of early death by 70 percent, according to new research.
The study suggests that more physical activity, particularly at higher intensities, could lead to a 'big' increase in life expectancy among females in retirement age.
Researchers at Harvard University found light-intensity physical activity, such as a walking a dog, doing housework, or window shopping, did nothing to improve or worsen longevity.
Experts say this research should drive doctors to prescribe more intense physical activity to their patients, particularly older females.
Previous studies, which used self-reports, showed that active people have about 20 to 30 percent lower death rates, compared to their least active counterparts.
The latest research, conducted from 2011 to 2015, is among the first to investigate physical activity, measured using a wearable device called a triaxial accelerometer.
The device is capable of measuring activity along three planes: up and down, front to back and side to side. The capabilities increase sensitivity to detect physical activity and allow for more precise measurements.
Study first author Professor I-Min Lee, of Harvard University's medical and public health schools in the US, said: 'We used devices to better measure not only higher intensity physical activities, but also lower intensity activities and sedentary behaviour, which has become of great interest in the last few years.'
More than 17,700 women with an average age of 72 wore the activity monitoring device for seven days.
Figures were analysed from 16,741 participants who wore their devices for at least 10 hours a day, on at least four days. During an average follow-up of around 30 months, 207 women died.
The researchers found that more moderate to vigorous intensity physical activity -such as brisk walking - was associated with roughly a 60 percent to 70 percent lower risk of death at the end of the study among the most active women, compared to the least active.
More light intensity activity - including housework or slow walking such as window shopping - or more sedentary behavior was not independently associated with death risk at the study's end.
The researchers stressed their finding does not mean light activity isn't beneficial for other health outcomes.
Prof Lee said: 'Younger people in their 20s and 30s generally can participate in vigorous intensity activities, such as running or playing basketball.
'But for older people, vigorous intensity activity may be impossible, and moderate intensity activity may not even be achievable.
'So, we were interested in studying potential health benefits associated with light intensity activities that most older people can do.'
She said the study's participants were relatively healthy, and mostly white women.
Prof Lee said the findings, published in the journal Circulation, support 2008 guidelines that suggest at least 150 minutes a week of moderate intensity or 75 minutes a week of vigorous-intensity aerobic physical activity - or a combination of the two - and muscle-strengthening exercises two or more days a week.
She added: 'We hope to continue this study in the future to examine other health outcomes, and particularly to investigate the details of how much and what kinds of activity are healthful.
'What is irrefutable is the fact that physical activity is good for your health.'