Spring in Motion: Cycling – Physical activity, collisions and air pollution

Ok, I’ll admit it. I’m a cyclist. My main mode of transportation is my bicycle. I ride most days of the year and have been since my first year of university. At the time my main motivation was cost. The $300 Norco Scrambler I bought at the Bike Doctor in 2001 got me through 6 years of bicycle commuting.
This is my second post for In Motion and, you guessed it, I’ll be talking about cycling and health. People typically assume that cycling is good for health because it contributes to physical activity, an important contributing factor to many different health problems like diabetes and mental health.1 But measuring the overall health benefits of cycling is a bit more complicated than that.
There is good evidence to show that cycling, and especially bicycle commuting on a daily basis is related to a number of positive health outcomes.2-6 For example, Wagner et al., showed that men who regularly walked and cycled to work had a BMI of 0.3 lower than those who did not walk or cycle to work.
But for all the physical activity benefits of cycling there are also risks: collisions and air pollution. A study published in the American Journal of Epidemiology showed cyclists have a fatal risk of 20.97 per million person trips, compared to motor vehicles with a fatal risk of 9.25 per million person trips.7Between 1993 and 2001 the total number of cyclist fatalities in the United States was 695 compared to 32283 fatalities for motor vehicle users. In terms of air pollution, cyclists inhale approximately 1% more pollutants than drivers.8
Now the question is, Overall, is cycling beneficial for health? The short answer is Yes. There are a few studies that have done just that.8-9 de Hartog et al., showed that if people made most of their short trips by bicycle instead of by car the estimated positive impact from physical activity would be between 3-14 months of life gained and the negative impact would be 0.8-40 days of life lost because of air pollution and 5-9 days of life lost because of collisions. So the overall positive impact of cycling for most short trips would be at a minimum 2 months and at a maximum 1 year of life gained for each person in the population.
So what does it all mean for you moving around your city?
Get on your bike for short trips. Bikes are about the same speed as cars on trips of less than 5km. Bikes help you get physically active and the risks of air pollution and collisions are low.
Daniel Fuller, PhD
Canadian Institutes of Health Research Post-Doctoral Fellow
Department of Community Health and Epidemiology
University of Saskatchewan
References:
1.     Warburton DER, Nicol CW, Bredin SSD. Health benefits of physical activity: the evidence. Canadian Medical Association Journal. 2006;174(6):801–809. doi:10.1503/cmaj.051351.
2.     Barengo NC, Kastarinend M, Lakkaa T, Nissinenc A, Tuomilehtoe J. Different forms of physical activity and cardiovascular risk factors among 24–64-year-old men and women in Finland. European Journal of Cardiovascular Prevention and Rehabilitation. 2006;13:51-59.
3.     Hu G, Pekkarinen H, Hänninen O, Tian H, Guo Z. Relation between commuting, leisure time physical activity and serum lipids in a Chinese urban population. Annals of Human Biology. 2001;28:412-421.
4.     Hu G, Pekkarinen H, Hänninen O, Yu Z, Guo Z, Tian H. Commuting, leisure-time physical activity, and cardiovascular risk factors in China. Medicine and Science in Sports and Exercise. 2002;34:234-238.
5.     von Huth Smith L, Borch-Johnsen K, Jørgensen T. Commuting physical activity is favorably associated with biological risk factors for cardiovascular disease. European Journal of Epidemiology. 2007;22(11):771–779.
6.     Wagner A, Simon C, Ducimetiere P, et al. Leisure-time physical activity and regular walking or cycling to work are associated with adiposity and 5y weight gain in middle-aged men: the PRIME study. International Journal of Obesity. 2001;25:940-948.
7.     Beck LF, Dellinger AM, O’Neil ME. Motor vehicle crash injury rates by mode of travel, united states: Using exposure-based methods to quantify differences. American Journal of Epidemiology. 2007;166(2):212–218.
8.     Johan de Hartog J, Boogaard H, Nijland H, Hoek G. Do the health benefits of cycling outweigh the risks? Environ. Health Perspect.2010;118(8):1109–1116.
9.     Rojas-Rueda D, de Nazelle A, Tainio M, Nieuwenhuijsen MJ. The health risks and benefits of cycling in urban environments compared with car use: health impact assessment study. BMJ. 2011;343(aug04 2):d4521–d4521. doi:10.1136/bmj.d4521.

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