Cell ageing appears to slow down if we keep fit and active, according to research at Brigham Young University in the US.
The study, published in the medical journal Preventive Medicine, found that people who exercised often had significantly longer telomeres than those who were more sedentary.
The size of telomeres (the protein ‘endcaps’ of our chromosomes) reduces with age, as they shorten every time a cell replicates.
The study’s authors analysed data from 5,823 adults. The data, from the National Health and Nutrition Examination Survey (NHANES), included information on telomere length and records of the physical activities participants engaged in.
It was found that the most sedentary people had the shortest telomeres compared to participants who were most active — 140 fewer base pairs of DNA at the end of their telomeres.
In white blood cells, telomere length ranges from 8,000 base pairs in newborns to 3,000 base pairs in adults. This can fall to as low as 1,500 in old age. Cells can divide between 50 and 70 times before they die, and in each division an average of about 115 base pairs are lost.
Researchers estimated that the difference between the most sedentary group and those who were most active — that is, those who exercised for at least two and a half hours a week — amounted to about nine years of extra cellular ageing.
Although the researchers did not establish how exercise affected telomere length, Larry Tucker, the study’s lead author, said it may be explained by inflammation and oxidative stress, which exercise is known to suppress. Previous studies have linked telomere length with these factors.
Tucker said: ‘The more physically active we are, the less biological ageing takes place in our bodies. If you want to see a real difference in slowing your biological ageing, it appears that a little exercise won’t cut it. You have to work out regularly at high levels.
‘We know that regular physical activity helps to reduce mortality and prolong life, and now we know part of that advantage may be due to the preservation of telomeres.’
This study investigated the relationship between physical activity and telomere length. The telomeres are nucleoprotein caps positioned at the ends of the 23 pairs of chromosomes that reside in each cell’s nucleus and contain our DNA. As humans age, the telomeres shorten. This results in the gradual deterioration of the cell in which they reside. Furthermore, telomere attrition and dysfunction have been shown to be causal factors in the acquisition of many age-related diseases, including heart attacks and dementia.
The study of 5,823 adults concluded that physical activity was associated with longer telomere length in the nuclei of white blood cells (leukocytes). They used the gold standard to measure telomere length — that is, they used polymerase chain reaction, which amplifies a small sample of DNA, thereby making it easier to measure.
However, there are drawbacks. First, a self-selected sample of educated and engaged individuals chose to take part in the survey and are unlikely to represent the US as a whole.
Second, it was a cross-sectional rather than longitudinal study and so, despite the claims in the media, one cannot conclude that physical activity influences telomere length over time, as this is measured at a single time point. An assumption is also made that the length of the telomere of white blood cells is representative of the rest of the nucleated cells in the body without directly measuring them.
Finally, physical activity was assessed using reported frequency, intensity, and duration of participation in 62 physical activities. This kind of record is notoriously unreliable and prone to exaggeration.