It is funny that one of the few areas of life where people feel able to criticise others’ approach to risk and safety is in cycling. I repeatedly hear people make comments about how I ‘should always wear a cycle helmet’ – this even after I explain that I have looked into the evidence and am making a conscious decision not to wear a cycle helmet for some journeys – e.g. cycling to shops or around town (note – I think the situation is rather different when cycling as a sport – at high speed, in a group etc; for this, I wear a helmet). So, how dangerous is cycling without a helmet – and if we’re going to criticise others’ for not wearing helmets while cycling, what else do we need to criticise them for?

Let’s compare to some other everyday things and see how dangerous it really is…all figures are from the UK, and while they may be from different years (because that’s what was available) they are representative.

Cycling deaths per year (2012 – total): 120

Cycling deaths that could have been prevented by cycle helmets – DfT figure: 12 – 19*

Walking deaths per year: 420

Deaths from inactivity caused Coronary Heart Disease/Stroke: 57,000 (McPherson, Klim, 2002)

Deaths from inactivity caused Cancer: 28,000 (McPherson, Klim, 2002)

Deaths due to smoking : 114,000 (NHS figure)

*Note this figure is widely questioned as detailed here, and should be considered an upper end estimate: http://tinyurl.com/oxm2a3r

About 25% of the population smokes, about the same proportion as cycle; the population judged to be ‘inactive’ is actually of the order of 75% of the population. We can put these numbers into a table showing risk per person carrying out each activity – let’s call it ‘Relative Cycling Helmet Stupidity Index’ – working out the risk of dying per person doing each activity and standardising it against the difference in risk between cycling with a helmet and cycling without.

Cycling helmet stupidity index Adjusted for health benefits All cycling 3 -39 Cycling w/helmet 3 -39 Cycling w/out helmets 4 -38 Difference in risk – w/helmets and w/out; 1 Walking 3 Risk from inactivity 759 Smoking related deaths 3054

So, so far we can see that in order to criticise those who choose to cycle without helmets, we need to criticise smokers 3000 times as much for putting their health at risk as cyclists; and those who are couch potato’s about 750 times more.

Note that the risk per person walking is roughly equivalent to the risk per person cycling (I assumed 100% of the population walks).

However, this is before we adjust for the health benefits of cycling. I added the inactivity figures to show that, as has been found repeatedly by medical studies, it is many times safer to ride a bike than not – here are a few example medical studies: “Benefits outweigh dangers 13:1” (Woodcock et al, 2009); “Life years saved outweigh those lost by 20:1” (Hillman, 1992), as well as this one which states a 77:1 benefit: risk ratio (but was carried out in Spain, not in the UK) http://www.bmj.com/content/343/bmj.d4521.

I used the most conservative estimate of the relative benefits to adjust for health benefits of cycling, which is the third column. The negative number in this column means that you are many times less likely to die if you cycle than not – even if not wearing a helmet. This is even when we use the most conservative number for the benefits; so the likely benefits are many times this number.

So in fact, you are 38 times more likely to live longer because you’re cycling, than to die because you’re not wearing a helmet. To be clear, on average, you are 38 times more stupid not to ride a bike, than you are to ride a bike without a helmet. That’s using the most conservative numbers available – the likely benefit:risk ratio is many times higher.

I believe in free choice and wouldn’t criticise anyone else for the choices they make – smoking or being inactive. I believe that people are best placed to make their own decisions. However, if you are to criticise others for not wearing a helmet I think that you’re missing the point. Especially if you don’t ride a bike yourself – who you calling stupid?