The study is published in the 28th January issue of the Archives of Internal Medicine, and is the work of Dr Lynn F Cherkas, of King's College London, and colleagues.
The researchers noted that previous research had already suggested that:
"A sedentary lifestyle increases the propensity to aging-related disease and premature death."
Regular exercise is linked to lower rates of high blood pressure, heart and circulation problems, type 2 diabetes, cancer, obesity and osteoporosis, they said.
But Cherkas and colleagues suggested their study showed that:
"Inactivity may diminish life expectancy not only by predisposing to aging-related diseases but also because it may influence the aging process itself."
In this study, 2,401 white twins (2,152 women and 249 men) filled in questionnaires about how much they exercised, whether and how much they smoked, and their socioeconomic status. All participants were healthy and they also gave blood samples so that their DNA could be examined.
The researchers were interested in the length of telomere sequences at the ends of the chromosomes in the participants' leukocytes or white blood cells, what they termed the "leukocyte telomere length" or LTL. These tend to get shorter as people age and are used as an indicator of a person's biological age.
To be precise, the researchers defined an LTL measure as the "mean terminal restriction fragment length", which is expressed in terms of structural units called nucleotides.
They found that on average, LTL decreased with age at a loss of 21 nucleotides per year.
After adjusting for age and other potential confounders, such as age, sex, body mass index, smoking, socioeconomic status, and physical activity at work, the results showed that men and women who were less physically active in their leisure time had shorter LTLs than those who were more physically active.
In addition, the results showed that:
- The LTLs of the most active participants were 200 nucleotides longer than the least active.
- The most active participants performed an average of 199 minutes a week of exercise in their leisure time compared with 16 minutes for the least active.
- The link between longer LTLs and physical activity was confirmed by looking at a subset of twins where one was physically active in his or her leisure time and the other was sedentary.
- On average, the LTL of the more active twins were 88 nucleotides longer than those of the less active twins.
"A sedentary lifestyle (in addition to smoking, high body mass index, and low socioeconomic status) has an effect on LTL and may accelerate the aging process."
They suggested this finding showed that "adults who partake in regular physical activity are biologically younger than sedentary individuals" and:
"Provides a powerful message that could be used by clinicians to promote the potentially antiaging effect of regular exercise."
Speculating on the reasons behind this link between longer telomeres and exercise, Cherkas and colleagues suggested that sedentary lifestyles probably increase inflammation and oxidative stress damage to cells.
Perceived stress levels have been linked to telomere length in other studies, and they suggest that by decreasing psychological stress, physical activity mitigates its influence on telomeres and aging.
They went on to point out the importance of following guidelines for physical exercise. The US guidelines for example recommend people have 30 minutes of moderate intensity physical activity on five days every week.
Dr Jack M Guralnik, of the National Institute on Aging, Bethesda, Maryland, USA, said that more research was needed to establish a direct link between aging and physical activity. In an editorial in the same issue of the journal he explained there could be other factors at play:
"Persons who exercise are different from sedentary persons in many ways, and although certain variables were adjusted for in this analysis, many additional factors could be responsible for the biological differences between active and sedentary persons, a situation referred to by epidemiologists as residual confounding."
But he added that:
"Nevertheless, this article serves as one of many pieces of evidence that telomere length might be targeted in studying aging outcomes."
Telomeres are thought to act a like a buffer zone of "useless" DNA on the ends of the DNA strands that protects the integrity of the useful information in our DNA because every time a cell divides and its DNA is copied, it loses some of the edges of the DNA. This is like every time you take a photocopy of a photocopy, the image creeps toward the edges and deteriorates, until eventually you lose the bits around the edge.
"The Association Between Physical Activity in Leisure Time and Leukocyte Telomere Length."
Lynn F. Cherkas; Janice L. Hunkin; Bernet S. Kato; J. Brent Richards; Jeffrey P. Gardner; Gabriela L. Surdulescu; Masayuki Kimura; Xiaobin Lu; Tim D. Spector; Abraham Aviv.
Arch Intern Med 2008;168(2):154-158.
Vol. 168 No. 2, January 28, 2008.
Click here for Abstract.
Sources: Journal article and press release.