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http://psychcentral.com/news/2008/01/29/physical-activity-keeps-cells-young/
1852.html

Physical Activity Keeps Cells Young
By: Rick Nauert, Ph.D.
Senior News Editor

Reviewed by: John M. Grohol, Psy.D.
on January 29, 2008

Tuesday, Jan. 29 (Psych Central) -- riding bikeA new report in the Archives
of Internal Medicine suggests individuals who are physically active during
their leisure time appear to be biologically younger than those with
sedentary lifestyles. Researchers discovered chromosomes in white blood
cells were more robust among active individuals, a finding that helps
explain the anti-aging effect of regular exercise.

Regular exercisers have lower rates of cardiovascular disease, type 2
diabetes, cancer, high blood pressure, obesity and osteoporosis, according
to background information in the article.

³A sedentary lifestyle increases the propensity to aging-related disease and
premature death,² the authors write. ³Inactivity may diminish life
expectancy not only by predisposing to aging-related diseases but also
because it may influence the aging process itself.²

Lynn F. Cherkas, Ph.D., of King¹s College London, and colleagues studied
2,401 white twins, administering questionnaires on physical activity level,
smoking habits and socioeconomic status. The participants also provided a
blood sample from which DNA was extracted. The researchers examined the
length of telomeres‹repeated sequences at the end of chromosomes‹in the
twins¹ white blood cells (leukocytes). Leukocyte telomeres progressively
shorten over time and may serve as a marker of biological age.

Telomere length decreased with age, with an average loss of 21 nucleotides
(structural units) per year. Men and women who were less physically active
in their leisure time had shorter leukocyte telomeres than those who were
more active.

³Such a relationship between leukocyte telomere length and physical activity
level remained significant after adjustment for body mass index, smoking,
socioeconomic status and physical activity at work,² the authors write. ³The
mean difference in leukocyte telomere length between the most active [who
performed an average of 199 minutes of physical activity per week] and least
active [16 minutes of physical activity per week] subjects was 200
nucleotides, which means that the most active subjects had telomeres the
same length as sedentary individuals up to 10 years younger, on average.² A
sub-analysis comparing pairs in which twins had different levels of physical
activity showed similar results.

Oxidative stress‹damage caused to cells by exposure to oxygen‹and
inflammation are likely mechanisms by which sedentary lifestyles shorten
telomeres, the authors suggest. In addition, perceived stress levels have
been linked to telomere length. Physical activity may reduce psychological
stress, thus mitigating its effect on telomeres and the aging process.

³The U.S. guidelines recommend that 30 minutes of moderate-intensity
physical activity at least five days a week can have significant health
benefits,² the authors write.

³Our results underscore the vital importance of these guidelines. They show
that adults who partake in regular physical activity are biologically
younger than sedentary individuals. This conclusion provides a powerful
message that could be used by clinicians to promote the potential anti-aging
effect of regular exercise.²

Source: JAMA and Archives Journals