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Exercise slows biological ageing.

Cherkas L, Hunkin J, Kato B, Brent Richards J, Gardner J, Surdulescu G, Kimura M, Lu X, Spector T, Aviv A. The association between physical activity in leisure time and leukocyte telomere length. Archives of Internal Medicine 2008;168(2):154-158.

Telomeres are DNA sequences which, along with associated proteins, protect chromosomes from degradation. Telomeres however become progressively shorter with each cell division. This shortening process is exacerbated by oxidative stress.

Inflammation results in an increase in leukocyte turnover. Thus these researchers postulated that leukocyte telomeres may effectively 'chronicle the cumulative burden of oxidative stress and inflammation, and, as such, serve as an index of biological age'.

Additionally, it is already known that shortened leukocyte telomere length is associated with diseases related to oxidative stress, such as diabetes and coronary artery disease. Leukocyte telomere length is also inversely correlated with the body mass index (BMI), that is a higher BMI is associated with a shorter leukocyte telomere length.

As the BMI reflects energy input and output, the researchers hypothesised 'that physical activity level may have an effect on telomere attrition independent of other risk factors influencing the aging process'. To test this hypothesis, the researchers studied 1,319 twins with a mean age of 48.8 years. To allow for the possible effects of menopause, female twins were stratified into two subsets, one subset under 50 and the other over 50 years of age.

Subjects were asked to complete questionnaires detailing their physical activity levels over the previous 12 months as well as currently. Height and weight were obtained during clinic visits, and blood samples were taken to enable the leukocyte telomere lengths to be measured.

The primary finding was that men and women who were less physically active had a shorter leukocyte telomere length than their more active peers. The mean difference in the length of leukocyte telomere length between the most active subjects and the least active was the equivalent of 10 biological years.

To reduce the effect of any random genetic or environmental impacts, the researchers also looked at 67 twins who were raised together, but who had discordant physical activity levels. The results in this twin subset were consistent with the overall results.

Additionally, as there were no significant differences in the occurrence of chronic diseases between the more and less active subjects, the reduced leukocyte telomere length in the less active subjects could not be as a result of a higher prevalence in that group of chronic disease.

In conclusion, the researchers found that:
 adults who partake in regular physical activity are biologically
 younger than sedentary individuals.

Their findings emphasised the importance of regular exercise to 'retard aging and diminish the risk of aging-related diseases'.

Comments: The study's results are consistent with an interesting paradox ie that exercise has been reported to increase oxidative damage, yet decrease oxidative stress related disease. The authors suggest that the controversial hormesis theory might explain this paradox. The hormesis theory suggests that benefits from low doses of potentially harmful substances could occur. In this instance, a benefit might result from exercise causing an increased anti-inflammatory response, and thus resulting in overall reduced levels of oxidative stress and inflammation.
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Title Annotation:Research Briefs
Author:Boylan, Matthew
Publication:Journal of the Australian Traditional-Medicine Society
Geographic Code:8AUST
Date:Mar 1, 2008
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