Does cycling really slow ageing?

In the science section of several media sites this week was a story about ageing and exercise. The headline in The Independent was ‘The secret of eternal youth: skin-tight Lycra and a bicycle’ and the story also appeared on Yahoo headlined ‘Study: Cycling slows ageing process’. A game I frequently like to play when viewing science in the media is look at the headline and imagine a rough plan of what would be required to test that statement or questions. Frequently the media have answered a question that the researchers themselves haven’t even asked. In this instance I imagined a study where a series of people had been followed throughout their lives, and cycling had been isolated as a factor that slowed the anti-ageing process, without being confounded by other factors that cyclists are likely to share such as a general active lifestyle. Cycling would also have to be compared with other forms of exercise to justify its solitary elevation as an anti-ageing tool in the media articles.

The original research paper that forms this story is an early online article from the Journal of Physiology ‘An investigation into the relationship between age and physiological function in highly active older adults’. The main thrust of the paper is about finding ‘biomarkers’ for ageing. This is basically identifying physiological factors that can be used to accurately age an individual. The main purpose of such a pursuit is to test possible interventions to slow the effects of ageing. Having a baseline where individuals could be accurately aged would allow any anti-ageing effects to be quantified, and compared against each other for the magnitude of the effects. The identification of biomarkers for ageing has proved problematic so far, as many factors affect the physiological decline with age we see. Genetics and lifestyle are two particularly important factors that result in candidate biomarkers being inaccurate predictors of age. The authors here argue that lifestyle is particularly important as a confounding factor, with a sedentary lifestyle having large impacts on physiological function that stop any biomarker being able to accurately age individuals, as in sedentary individuals physiological decline occurs due to that lifestyle, as well as due to time.

To resolve this issue the authors decided to use a subset of people, who lead active lives. The reasoning for this is that in theory these individuals have not damaged their physiology through inactivity, so it should be possible to predict certain factors based on their inevitable decline with age. Elderly cyclists were chosen as a rather arbitrary group, as activity levels are high. Cardiovascular, respiratory and cognitive factors were amongst the candidate biomarkers, alongside factors such as bone density. The results were that, although some factors showed a trend towards a decline with age (as biomarkers are predicted to do) variation was high, and no factor was able to accurately predict age. VO2 max (maximum oxygen consumption) was the best predictor. These results show that sedentary lifestyles aren’t the full explanation for the lack of effectiveness of biomarkers in predicting age. Ageing is a highly individualistic process, with declines not happening consistently across individuals, even when removing the effects of a sedentary lifestyle. There are still genetic differences that this paper can’t account for, and the study is also cross-sectional which causes problems (see explanation later) but this is still a highly interesting result, that casts doubt on the likelihood of biomarkers being able to accurately pinpoint age, and opens up several avenues for future studies.

The paper is very good, and certainly worthy of attention, but its transformation into a justification of cycling as a means of holding back father time is an inaccurate representation of what the paper was all about. The paper isn’t about the merits of cycling to slow ageing, it is well known that an active lifestyle can have positive effects on physiological function, and no attempt has been made to compare cycling to other forms of exercise. The authors themselves state ‘In the absence of clear evidence defining the amount of exercise necessary to combat the negative effects of inactivity, we pragmatically set standards for acceptance into the study’. The main argument of the paper is about ageing still being highly varied and individualistic, even when removing the effects of exercise levels. So, at what stage did this research morph into a praise of cycling as a way of turning back time? The general method of scientific papers reaching the press is through universities releasing press releases, which then form the skeleton of articles in the media. Recent research in health has begun to look at the roll of press releases in reflecting research, and influencing media articles. An article in the BMJ found that over a third of press releases on health research from 20 top UK universities contained exaggerated advice, claims of causation for correlational studies, or unjustifiable applications of animal studies to human health. Tellingly this then passed on to news articles. When exaggeration was present 58-86% of articles featured the same exaggeration, compared to 10-17% of articles containing exaggeration where it wasn’t present in the press release. An editorial by Ben Goldacre makes several suggestions to counter the problem of misleading press releases, including accountability of authors (both press and academic), transparency and feedback.

Miscommunication of science is common in the media, and universities themselves need to take more responsibility to ensure that they aren’t causing this. News outlets respond to the authority of universities, and at present many universities clearly aren’t standing up to that responsibility by ensuring their communication of science is accurate and clear. Many researchers now use social media to communicate their work, and websites such as theconversation.com allow readers to receive news direct from the authors, but the mainstream media still uses press releases to write their stories, and academics and universities need to take greater responsibility. The title of the press release for this article? ‘Exercise allows you to age optimally’ followed by a picture of a bicycle.

A quick side note – cross sectional vs longitudinal studies

The study in question is cross sectional, meaning that when looking at a ‘decline’ with age, we are actually looking at a difference between people of one age compared to people of another age. This is different to longitudinal studies where individuals would be followed throughout the time period, so any decline would be an actual decline within an individual. To illustrate the issues with cross sectional studies consider the following example.

telomeres

This is hypothetical data describing a real pattern found in a bird species, Leach’s storm petrel. The y axis displays telomere length. Telomeres are sections of DNA that form a protective cap on the end of chromosomes. Each time a cell divides the telomeres get shorter, until they reach a critical point where cell division can no longer occur. In this example it appears that Leach’s storm petrel’s telomeres are getting longer with age. Telomerase is an enzyme which can repair telomeres, as this result would suggest that the action of telomerase and the lengthening of telomeres is important for lifespan in this species. However, this data is cross sectional – meaning that age 1 on the graph is completely different individuals to age 8. An alternative explanation for the results is that as this is telomeres might not be getting longer, there might be large variation in telomere length in youngsters, and something about long telomeres to start with makes you more likely to live to old age, making the average telomere length longer for old birds, and giving rise to the apparent lengthening of telomeres. This hypothesis would suggest that it is having long telomeres to start with that is important, not having ones that get longer. Only a longitudinal study could fully detect what was happening.

Links and references

http://www.badscience.net/2014/12/my-bmj-editorial-on-academic-press-releases-routinely-misleading-the-public/

http://mbe.oxfordjournals.org/content/25/1/220.full

http://www.kcl.ac.uk/newsevents/news/newsrecords/2015/January/Exercise-allows-you-to-age-optimally.aspx

http://www.independent.co.uk/sport/cycling/the-secret-of-eternal-youth-skintight-lycra-and-a-bicycle-9959058.html

https://au.lifestyle.yahoo.com/prevention/a/25920895/study-cycling-slows-ageing-process/