Tuesday August 12 2008
Be fitter and live longer
“Running can slow the effects of ageing and give older people a new lease of life”, the Daily Mail reported. It said that researchers have found that runners are half as likely to die prematurely as non-runners, that they remain fit and active for longer, and are less likely to suffer from cancer, heart disease and neurological disorders.
These findings come from a well-conducted study of middle-aged and older runners. Despite some limitations, this study reinforces the idea that exercise helps you to live longer and to keep able-bodied. Vigorous exercise such as running may not be suitable for all people, and those who wish to start, but have specific health concerns (for example, high blood pressure or obesity), should take advice from their doctor. Those who are unable to perform vigorous activity can consider low-impact activity as an alternative.
Where did the story come from?
Dr Eliza Chakravarty and colleagues from the Stanford University School of Medicine carried out the research. The study was funded by the National Institute of Arthritis and Musculoskeletal and Skin Diseases and the National Institute on Aging, National Institutes of Health. The study was published in the peer-reviewed medical journal: Archives of Internal Medicine.
What kind of scientific study was this?
This was a prospective cohort study looking at the long-term effects of running on survival among older adults.
In 1984, the researchers enrolled 961 people in the USA who were aged 50 and above to take part in their study. Runners were identified through a national running club, while control participants were identified from Stanford University staff and faculty. All participants had to have at least high school education. The researchers sent questionnaires to those interested in participating, and 538 runners and 423 controls (average age 59 years) were willing to participate and returned these. The questionnaires asked about medical history, demographic information, exercise habits, and measured level of ability in functional activities of daily living (such as grooming, hygiene, and eating) using a standard set of eight questions (the Health Assessment Questionnaire Disability Index - HAQ-DI).
Each of the eight areas on the HAQ-DI is scored from zero (no problems with listed activities) to three (unable to perform listed activities). A score between 0.5 and one indicated moderate disability, and one or above indicated severe disability. Participants filled in the questionnaire annually once the study began. Self-reported running activity was checked against information obtained from doctors or trained observers for a subset of the runners, and the two sources were found to be in “excellent” agreement, validating the questionnaire.
So that it would be representative of the general community, the control group also included people who performed vigorous exercise, including running. In order to see how this affected results, the researchers grouped all the participants into ‘ever runners’, people who had ever run for a period of one month (which could include people in the control group) and ‘never runners’, people who had never run at all.
The researchers searched the National Death Index to identify study participants who had died, and their cause of death, up to 2003. Deaths to this date and change in functional disability (measured on the HAQ-DI) up to 2005 was compared between runners and controls, and ever runners and never runners. Analyses took into account other factors that might also have had an effect, such as disability at the start of the study, age, gender, smoking, BMI, and weekly aerobic exercise. A total of 284 runners and 156 controls (46% of those enrolled, 60% of those alive) completed the 21-year follow-up (1984 to 2005).
What were the results of the study?
At the beginning of the study, runners engaged in about four hours a week running on average, and about five hours vigorous exercise a week in total. The control group engaged in an average of 15 minutes a week running, and about 1.5 hours vigorous exercise a week in total. The researchers found that runners were younger, less likely to smoke, more likely to be male, had lower BMIs, and lower functional disability levels than controls at the beginning of the study.
Over time, functional ability declined in both groups, but this decline was significantly less among the runners than the controls. Runners were about 50% less likely than controls to develop moderate functional disability during follow up. Analyses comparing ever runners with never runners had similar findings.
Overall, there were 225 deaths during the study (23% of those enrolled), 81 among the runners (15%) and 144 among the controls (34%). Runners were about 39% less likely to die from any cause during follow up than controls, after taking into account potential confounding factors. When looking at specific causes of death, runners were less likely to die from cancer, cardiovascular, neurological or infectious causes.
What interpretations did the researchers draw from these results?
The researchers concluded that vigorous running in middle and older age reduces disability in later life and lengthens life.
What does the NHS Knowledge Service make of this study?
This is a well-conducted study, but there are some limitations inherent in its design:
- As with all studies of this type, there may have been differences between runners and controls other than their running that accounted for the differences observed in survival rates. The researchers made attempts to control for potential differences, but could not adjust for all factors. In particular, they did not assess and make any adjustments for diet.
- This study only looked at people who survived to middle age. These results may therefore not reflect what would be seen at younger ages.
- As the study was quite long, a relatively high proportion of people dropped out of the study and this may have affected disability results (mortality data were available for 100% of participants). Those who dropped out from the control group were more likely to be older, to run less, and have less disability at the beginning of the study; there were few differences between completers and non-completers among the runners. This suggests that the differences between runners and controls may have been even greater if these people had been followed up.
- People enrolled in this study were all educated to high school or above, were mostly white, had low levels of smoking and alcohol use, and were not obese or overweight. These results may therefore not be representative of what might be found in people from different ethnic groups or backgrounds.
Overall, this study reinforces the idea that exercise is good for you, and helps you to live longer and to keep able-bodied. People who are middle-aged or older, who have led a sedentary lifestyle to date but who wish to begin taking vigorous exercise, should take advice from their doctor, ensure that they are wearing appropriate clothing, particularly shoes, and build up the level of exertion gradually.
Sir Muir Gray adds...
The evidence is beyond challenge. All forms of exercise: running, walking, dancing, press-ups or the Wii prevent disease and make you feel better. The older you are the greater the benefit.