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 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.


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


From the archives; I originally wrote this in March, 2013

This week has seen news of a new plan to control the highly invasive brown tree snake on the island of Guam. The plan involves toxic mice, and has met with fierce opposition from animal rights groups such as PETA.

First it is important to know a bit of background about Guam, and its large snake problem. Guam is a small island around 2000km north of Papua New Guinea, in the western Pacific. As a U.S territory its economy benefits from the location of an American military base, but its main source of income and jobs is the tourism industry.

For the past 70 years or so the people of Guam have shared their island not only with their rich native fauna, but also with an invader of great consequence, the brown tree snake (Boiga irregularis). There are well documented ecological factors that make some species more susceptible to extinction from invasives than others, and unfortunately island species tend to fit these criteria. Since its arrival the arboreal snake has freely expanded its population to its now huge density.

The impacts of this come in two interlinked flavours. Firstly, impacts on native wildlife; the snake has caused the local extinction of almost all native birds and reptiles, including the endemic Guam Flycatcher (now extinct) and the Guam Rail (now being bred in captivity for reintroductions elsewhere). 9 of 11 forest bird species previously found on Guam no longer occur there. As always with invasives, the impacts don’t stop there. Through impacts on the birds (which are important pollinators) native plants are also in decline. Secondly, impacts occur through conflict with people. Numerous power outages are directly caused by the snakes, along with a decline in tourism over and above that expected from purely the negative effects of the global recession.

So what are the U.S Department of Agriculture doing about this problem, which is having undisputed and hugely negative effects on the people of Guam and their wildlife? This is where we revisit the news that has been widely reported this week. The USDA are planning to use helicopters to drop dead mice laced with the chemical acetaminophen and attached to small parachutes, in order to kill the snakes and reduce the population. Now, firstly it pays to get to the root of the story, ideally a publication or press release from the organisation in question. A quick search led me to see that this story isn’t new at all. National Geographic reported in 2010 that the “toxic mice” were being airdropped in Guam. And the USDA have published reports detailing their efforts in controlling the snakes, and have been using acetaminophen since 2001. The primary concern of groups opposing the plans (ie PETA) is that the drug induces coma and death in the snakes, and takes up to 60 hours to have its affect. Other concerns are that airdrops are simply too random, and effects on non-target species are likely to be large.

These are all legitimate concerns, and animal rights groups play an important role in ensuring we aren’t exploiting species, but In this case I believe people need to do more research before they flat out refute something. Gone are the days when nations would take drastic biological decisions without a seconds thought (eg the disastrous use of myxomatosis to control Australia rabbits). The USDA conducts active research into plans to control invasives. A report from 2007 tested various types of parachute for the dead mice to reduce accidental death of non-target species – mainly coconut and hermit crabs. Far from the random and gung-ho approach the media have enjoyed portraying this is, it is a lot more calculated than that.

In terms of effectiveness this tactic appears to have a high potential, the fact that the brown tree snake will eat prey it has not consumed itself is fairly rare in snakes and is a weakness that conservationists need to exploit, in much the same way medical research looks for weaknesses in viruses. The cruelty issue is a tough one, without getting into a debate of the pain feeling abilities of reptiles, it is a cruel thing to do to any animal, and the snakes didn’t ask to be stowaways and transported to Guam. Having said that, I have come to the conclusion that it is a necessary evil. The USDA currently removes around 7000 snakes a year, out of an estimated population of over 1 million. That statistic alone shows that current efforts just aren’t going to be enough to ever make a serious change. There are also concerns that despite the presence of expert snake detecting dogs at all airports and ports on Guam the snakes could spread to other vulnerable islands. The opportunity is here to make a real dent in the snake population, and improve the livelihood of the people of Guam also. Focussing purely on the cruelty is not looking at the real picture, of the knock on effects on other species and people that this species is having. Sometimes conservation has to be cruel.

brown tree snake


Below is a response to a paper published in Science March 2013 about legalizing the trade in Rhino horn.

Original paper can be found here:

Response to Biggs et al (2013) Science 339

Biggs et al put forth the case the now is the time to legalise the trade in rhino horn, as the best option we have left. Whilst the overall argument of proponents of this idea is convincing and provocative, Biggs argument was much reduced, and featured several key omissions. An article in a journal such as this is sure to reach a huge audience, but the opportunity to present a compelling argument for legalisation of a trade that is inherently abhorrent to many people was somewhat missed.

When mentioning current destinations for horn, the authors mentioned Yemeni daggers and traditional Chinese medicine, and yet failed to mention Vietnam. Demand for horn in Yemen is actually decreasing whilst that in Vietnam appears to be driving the ever increasing poaching levels. It is a crucial error to miss out Vietnam, where a politician is said to have started the now widespread idea that rhino horn can cure cancer. The “cure” is now also being marketed and extended to maladies such as hangovers. Failure to mention this growing demand centre is a worrying sign. It is also of great importance when it comes to predicting the implications of legalising the trade. A lack of case studies prevent anyone from truly knowing what will happen if the trade is legalised, and yet this doesn’t stop the authors making spurious claims. The potential of a huge increase in demand is answered by the authors asserting that with stockpiles and harvesting a growing natural population future demand can be met. Whilst current stockpiles are estimated to be sufficient for ~20 years of current demand, we have no knowledge of how demand will change, and claims that natural harvesting can meet an unknown demand are inherently dubious. One key point that the authors neglected is the potential that legalising the trade could give legitimacy to Vietnamese claims that rhino horn is a broad cure for common illness. This could potentially hugely increase demand, beyond that sustained by natural harvesting. The authors back up their idea that demand may not increase by refuting claims that one off sales of elephant ivory to China in 2008 increased demand and/or poaching. Whilst concrete empirical evidence is indeed lacking, it is foolish to think that demand and poaching of elephants has decreased. Another issue with this, is that even if poaching wasn’t to increase, and we don’t know if that is true, demand is the key variable of interest.

Criminal syndicates who transport horn from Africa to Asia often do so under the protection of fraudulent CITES paperwork. One could easily argue that a complete legalisation of the trade will make the illegal trader easier, and not halt it. This may result in illegal trade still finding its way into the market. There is also the current international issue that trade and use of rhino horn is illegal in all destination countries, so any decision of African countries to legalise trade has to occur concurrently with Asian legalisation, something they may be reluctant to agree to. At this point, criminal syndicates in Asia would still benefit from a legal trade.

Biggs et al briefly mention a ‘safeguard’ against legalisation going badly wrong, namely halting the legal trade. A counter argument to this is that the damage done in this scenario would be huge. The potential Asian market for horn is 2 billion people, and the more people exposed to horn, the more who are likely to demand it. For this reason it can be argued that legal trade is largely irreversible without huge negative effects, and therefore needs to be thoroughly and meticulously planned, not rushed into.

I am inclined to agree that, in time, a legal trade is going to be the only card left to play. Killing poachers isn’t an effective conservation action, as the incentives present a seemingly limitless supply of potential poachers. Whilst acknowledging that time isn’t something available in abundance to Rhino, the framework for a legal trade simply isn’t yet in place. Under the values of the precautionary principle we need evidence that legalisation won’t cause an explosion in demand. Populations of Black Rhino are still increasing, and until we have more information on the impacts of a legal trade, and plans of how precisely it will work, the focus is still rightly on preventing poaching, and, of utmost importance, education and awareness in Asia.

© Brent Stirton / Veolia Environnement Wildlife Photographer of the Year 2012

© Brent Stirton / Veolia Environnement Wildlife Photographer of the Year 2012