It should come as a surprise to no one that physical activity and exercise is good for you. What may come as a surprise to many is just how good it can be. Research reported in the British Medical Journal last week indicates that cycling to work has extraordinary health benefits.
The research was carried out by a team of investigators at the University of Glasgow. They tracked 263,450 people for five years who traveled to work and lived in England, Scotland or Wales.
The participants in the study were categorized based on the mode of transportation they took to and from work. The categories and their definitions are shown in the following table.
|Transportation categories||How people got to work|
|Non-active||Car, public transit or both|
|Cycling||Cycling or cycling plus some walking|
|Mixed-mode walking||Mixture of walking with car and/or public transit|
|Mixed-mode cycling||Mixture of cycling or cycling plus some walking with car and/or public transit|
The frequency of illness or death from different causes was measured within each of the categories. The researchers measured death from all causes, cancer incidence and death, and cardiovascular disease incidence and death. Cancer and cardiovascular disease are the leading causes of death in both the UK and the US.
There are many factors that affect cancer and cardiovascular disease in addition to how a person travels to work. The researchers went to great lengths to control many of these factors. The analyses were carried out controlling for sex, age, ethnicity, deprivation (measured as a combination of household unemployment and overcrowding, and non-ownership of a car or home), other illnesses such as diabetes, hypertension and depression, body mass index, smoking, diet (alcohol, fruits and vegetables, red meat, oily fish, poultry, and processed meat), time spent walking for pleasure or engaged in strenuous sport, level of occupational physical activity, and sedentary behavior. This was an exceptionally well-controlled study.
The effects of walking and cycling were measured by comparing them with the Non-active mode of transport. Cycling to work was associated with very large health benefits. Commuters who cycled to work had a 41% lower risk of dying from all causes than people who drove or took public transport. They also had a 46% lower risk of developing and a 52% lower risk of dying from cardiovascular disease, and a 45% lower risk of developing and a 40% lower risk of dying from cancer.
Mixed-mode cycling was associated with good benefits that were not as large. Mixed-mode cyclists had a 24% lower risk of dying from all causes. They had a 32% lower risk of developing and a 36% lower risk of dying from cancer. There were no significant associations between mixed-mode cycling and cardiovascular disease.
Walking to work was associated with a 27% lower risk of developing and a 36% lower risk of dying from cardiovascular disease. There were no significant associations between walking and any of the other measures. There were also no significant associations between mixed-mode walking and any of the measures.
All of the observed benefits for both cyclists and walkers increased with the distance traveled. This is important because it means that even if you live too far from your job to cycle the entire distance, your health can benefit if you can ride a bike part of the way each day.
One might be inclined to question the beneficial effects associated with cycling to work that are reported in the study simply because they are so large. Although the study was very well done, there are, as always, limitations. The researchers point out that they were unable to control for obesity and the participants in their study may have been healthier on average than the general population.
In addition, the mode of transportation and the distance traveled were reported by the participants, not objectively measured by the investigators. Self-reported data is usually subject to higher degrees of bias, distortion or inaccuracy. Finally, while the study measured associations between health outcomes and modes of transit using a well-controlled prospective design, the evidence for a strong association between cycling and better health does not justify the conclusion that cycling was the cause of the observed health benefits.
The results of this study are of obvious interest to anyone who travels to work and wants to avoid cancer and cardiovascular disease. The study should also be of interest to employers and municipalities.
Cancer and cardiovascular disease are debilitating illnesses that have long-term effects. The study indicates that employers can reduce time lost due to illness by making it easy for their employees to cycle to work. It also suggests that the costs borne by municipalities for long-term treatment of people with cancer and cardiovascular disease can be reduced by making city streets safe and friendly for cyclists.
Moreover, the size of the effects seen in the study indicate that the benefits reaped by employers and municipalities are likely to be substantial. Encouraging people to ride their bikes to work while making it safe for them to do so is a win-win for everybody.