"Exercise in midlife protects heart," says BBC News, while the Daily Mail tells us that "gardening, walking and DIY in your fifties can cut risk of heart disease".
The news is based on a large study looking at the health of middle-aged people. Researchers found that those who met physical activity recommendations of at least 2.5 hours of moderate to vigorous exercise a week had lower levels of inflammation in their body compared with people who did not get enough exercise.
Reducing levels of inflammation is important as persistent inflammation, even at relatively modest levels, is thought to contribute to the adverse effects of ageing. For example, it is thought to contribute to loss of muscle power and strength, cardiovascular disease or CVD (conditions that affect the heart and blood vessels) and depression.
Interestingly, the results were independent of body fat. This suggests that exercise was still of significant benefit for people with no, or little, previous history of exercise.
The study had some limitations, including the fact that it measured markers of inflammation rather than CVD rates themselves. Nevertheless, this was a well conducted study that reinforces the health benefits of even moderate exercise.
Where did the story come from?
The research was part of the Whitehall II study and was carried out by researchers from University College London, Semmelweis University Faculty of Medicine in Hungary and INSERM in France. It was funded by the UK Medical Research Council and a number of UK and international sources. The individual researchers were supported by research grants from a range of different bodies including the European Union, the Academy of Finland and the Wellcome Trust. The study was published in the peer-reviewed journal Circulation.
This story has been covered by the BBC, The Daily Telegraph and the Daily Mail. The news coverage was accurate.
The media coverage of the study focused on the fact that the average age of the participants was almost 50. However, although this was the case, the study did not address when in your life exercise is the most beneficial. The Department of Health recommends that all people, whatever their age, take part in regular physical activities.
What kind of research was this?
This was a prospective cohort study that aimed to examine the association between long-term physical activity behaviour and low-grade inflammation over a 10-year follow-up period.
Although a cohort study was the appropriate study type to investigate the association between exercise and inflammatory markers, it cannot prove that exercise directly caused the differences.
A randomised controlled trial (RCT) with a long follow-up would be required to show direct cause and effect (causation). However, such a trial would be unethical to perform as people in a control group who were told not to exercise could damage their health.
What did the research involve?
Participants were part of the Whitehall II population-based cohort, which aimed to investigate social and occupational influences on cardiovascular disease risk. This study used data from 4,289 men and women who were recruited from the British civil service, who were 49 years old on average.
These people answered questions about the frequency, the amount and the intensity of activity they did in a week. This information was collected in 1991-1993 (the study start), 1997-1999 and 2002-2004 (the study end). The participants were analysed separately depending on whether they followed physical activity guidelines of at least 2.5 hours a week of moderate to vigorous physical activity.
Moderate-intensity exercise is defined as working hard enough to raise your heart rate and break a sweat, such as walking fast or pushing a lawn-mower. Vigorous-intensity exercise is defined as any exercise that causes a person to breathe hard and fast and significantly accelerate their heart rate, such as jogging or riding a bike at speed.
During each of the three time periods, the study participants were also clinically examined, had their height, weight, waist and hip circumference and blood pressure measured, and answered health and demographic questions.
A fasting blood sample was also taken, so the levels of two proteins known to be associated with inflammation – C-reactive protein and interleukin-6 – could be measured.
The researchers examined associations between baseline physical activity and long-term physical activity and inflammatory markers, after adjustment for:
- employment grade
- body mass index
- chronic (long-term) illness
What were the basic results?
The researchers found that approximately half of the study’s participants stuck to the recommended 2.5 hours a week of moderate to vigorous physical activity across all three assessments over the 10 years. Fulfilling the physical activity recommendations was associated with lower levels of inflammatory markers at baseline. There was no significant association between physical activity levels at baseline and change in the levels of inflammatory markers over time. This meant that the difference remained stable.
People who fulfilled the physical activity guidelines at all points during follow-up had lower levels of inflammatory markers than those who only fulfilled the guidelines at one point of follow-up, if at all. In addition, people who reported an increase in physical activity of at least 2.5 hours a week during the study had reduced inflammatory markers compared with those whose activity levels remained stable.
The researchers found that these associations were independent of measures of ‘fatness’ such as BMI or waist circumference. This is important because fatness could be used to explain the association seen, as people who adhered to the physical activity guidelines tended to have lower BMI, and fat tissue is a key site for the production of several inflammatory markers.
The fact that the association remained even in people with higher BMIs or waist circumference suggests that exercise can still benefit people who are overweight or obese with no previous history of exercise. As the Mail’s headline says, “it is never too late” to start exercising.
The researchers also found that people with higher levels of inflammatory markers at baseline had reduced physical activity over the follow-up period. This may be because inflammatory processes are thought to be involved in loss of skeletal muscle and functional decline.
So, while exercising in middle-age can bring important benefits, to achieve the greatest potential benefit from exercise, people should aim to remain physically active throughout their lives.
How did the researchers interpret the results?
The researchers said: “Regular physical activity is associated with lower markers of inflammation over 10 years of follow-up and thus may be important in preventing the pro-inflammatory state seen with aging”.
This study has found that people who did at least 2.5 hours of moderate to vigorous exercise regularly had lower levels of inflammatory markers over 10 years of follow-up. Levels of inflammatory markers gradually increase with age, and they are thought to play a role in the development of cardiovascular disease and other age-related conditions.
This was a prospective cohort study, which used people from a well understood cohort (the Whitehall II cohort, which recruited participants from the civil service). Participants in the study were followed for a long period, and measurement of all the exposures and outcomes of interest were taken repeatedly. However, although a cohort study was the appropriate study type to investigate the association between exercise and inflammatory markers, it cannot prove that exercise directly caused the differences as other unmeasured factors may have contributed. Also, when interpreting the results it is important to consider that the researchers measured inflammatory markers rather than the incidence of cardiovascular disease. Also, the study collected levels of activity using a questionnaire, which means that levels may not have been reported accurately. Finally, most of the people in the active group were men, so this finding may not apply to women.
However, this study adds weight to the case for regular exercise. The news coverage has focused on the fact that the average age of the participants was almost 50 years old, showing that exercise is beneficial at any age.
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