When seeing a shocking headline, it’s useful to turn it around. The Telegraph brings news that “Pollution wipes out the benefits of walking”. Turn it about and its reads: “Walking wipes out the harm caused by pollution.” Given that it’s cheaper to walk than it is to stop polluting, the solution to better health is simple, right?
The news is rooted in a study by the Imperial College London and funded by the British Heart Foundation, which looked at a sample of the over 60s, inviting 119 people to take a single two-hour stroll through London’s Hyde Park and neighbouring Oxford Street. The park stroll was good for the lungs, opening them up and improving arterial flexibility by up to 24%. But walk down the bus car park that’s Oxford Street and the walkers saw less improvement in lung capacity and up to 4.6 per cent rise in artery flexibility.
The Telegraph is putting a spin on the news. But in the Huffington Post it gets more confusing. It says:
Volunteers who took a walk in Hyde Park experienced a decrease in the stiffness of their arteries, a benefit normally seen after exercise. In contrast, volunteers who walked on Oxford Street had a “worrying increase” in artery stiffness following exercise.
You can read the study in full here. And it suggests that the media is picking data. The walkers’ health and what medication they were on might be vital. It might even be that some drugs prove an effective barrier to the detrimental effects of pollution.
The study’s authors write:.
In healthy participants, walking in Hyde Park led to a reduction in arterial stiffness that persisted up to 26 h, a benefit that was not only lost but even reversed after walking on Oxford Street. Participants with COPD or ischaemic heart disease also exhibited a reduced pulse wave velocity after walking in Hyde Park but increased pulse wave velocity after walking on Oxford Street. All three groups showed reductions in augmentation index following Hyde Park; and this beneficial change was significantly attenuated (even reversed at a few timepoints) after the Oxford Street walk.
Imperial says CODP is “a chronic lung condition linked with smoking”. It continues:
There are some limitations to this study. Because we did not include a resting control group, it would not be possible to be certain that walking contributed to the changes in lung function or arterial stiffness.
Our short-term study is unlikely to inform on the long-term benefits of exercise in relation to pollution. Moderate physical activity might protect against the adverse effects of air pollution on arterial stiffness
We have noted that adults free of chronic cardiopulmonary diseases lose the benefits of walking on pulmonary and cardiovascular function in a polluted environment. In participants with COPD and ischaemic heart disease exposed to traffic pollutants, the pulmonary benefit from walking seem to be lost too, but the improvement in arterial stiffness caused by walking is relatively well preserved in ischaemic heart disease participants, likely due to concomitant routine medication use.
So if you’ve got a sickly heart, walking in polluted environment might not do you as much good as walking in the park.
In 2016, Imperial College reported: “Walking and cycling in cities is good for health, despite worse air pollution.”
Dr Marko Tainio from the MRC Epidemiology Unit at the University of Cambridge, who led the new study, said:
“Our model indicates that in London health benefits of active travel always outweigh the risk from pollution. Even in Delhi, one of the most polluted cities in the world – with pollution levels ten times those in London – people would need to cycle over five hours per week before the pollution risks outweigh the health benefits.
“We should remember, though, that a small minority of workers in the most polluted cities, such as bike messengers, may be exposed to levels of air pollution high enough to cancel out the health benefits of physical activity.”
“These findings are important as for many people, such as the elderly or those with chronic disease, very often the only exercise they can do is to walk,” said senior author Fan Chung, Professor of Respiratory Medicine and Head of Experimental Studies Medicine at National Heart & Lung Institute at Imperial College London. “Our research suggests that we might advise older adults to walk in green spaces, away from built-up areas and pollution from traffic,” he added.
It’s interesting. But to look at the study and thunder “Air pollution wipes out benefits of exercise” as the Telegraph and Indy do it misleading.