Written by Alan Barker, Freelance Writer, British Science Festival 

How do you decide whether someone who has had a seizure can have a driving licence? Dr Laura Bonnett of the University of Liverpool has been using statistics to answer that question. Laura is delivering this year’s Rosalind Franklin Award Lecture for physical sciences and mathematics at the British Science Festival.

Ahead of her talk, Alan Barker spoke to her.

Dr Laura Bonnett's work has helped change the DVLA guidelines

How big a problem is epilepsy in relation to driving?
Well, the majority of people in the UK have a driving licence. One in a hundred of those will have epilepsy. We can’t predict when seizures or fits might happen – and it could be when you’re driving. So the DVLA has to set guidelines as to when you can return to driving after having a seizure.

So how do they set the guidelines?
Originally, they gathered together a group of clinicians, who looked at the risk of a newly qualified driver having an accident in their first year of driving – which is about 20% – and they simply transferred that estimate to the risk of an epileptic seizure behind the wheel. So they said: “About a year sounds ok.”

Seems more or less like guesswork.
You might say that. And that’s where I came in. I asked: “Don’t we need some evidence for this?” I was able to gather some relevant data which suggested that we could reduce the 12-month ban.

The majority of people in the UK have a driving licence, and one in a hundred of those will have epilepsy

What’s your data?
We’ve lots from randomised control trials, where we’ve recruited people to try out different treatments. And we have some data from GPs.

Epilepsy’s fascinating – statistically – because there are 45 different seizure types; people can have one seizure type very rarely, or multiple seizure types in one day. This makes it really hard to predict what will happen.

And have you managed to change the guidelines?
Yes. The limit after a first ever seizure has been reduced from twelve months to six months, based on our work. And the EU has followed suit. We’ve also provided other evidence for other guidelines to do with repeat seizures.

Job done, then.
Well: the story doesn’t stop there. We have to balance my statistical analysis with the needs of policy makers, and the needs of people living with epilepsy – and indeed the risk to the general public. We must balance the risk of having a seizure with the risk of someone not being able to lead a normal life. We’re working where statistics meets policy.

How do you lobby for your ideas to be accepted by policy makers?
That’s a really good question. In this instance, my clinical boss, an expert on epilepsy, sits on the neurology panel. But the neurology panel is the first within the DVLA that includes this statistical expertise. All the other medical panels – for other conditions – still base their policies on expert opinion. Don’t get me wrong: our analysis suggests that the clinicians’ guesses are largely valid, at least with epilepsy.

How have policy-makers reacted to your work?
There’s a real challenge for all of us. If I were making policy, I would adjust things to account for the type of seizures you’ve had, how long you’ve had epilepsy and so on. But the policy makers want a one-size-fits-all policy – so that it’s fair, and so that people report honestly.

Understandably, honest reporting can occasionally be a problem

Is honest reporting a problem?
Of course. People want a driving licence. That’s understandable. But if people are having lots of seizures, they’re likely to report anyway, because they want treatment. So it kind of all comes out in the wash.

Does your work have implications for other areas?
Oh yes. I’d certainly like other expert panels in the DVLA to use statisticians.

Any condition in particular?
Diabetes. It’s a growing problem; there’s no cure; and we have problems with reporting. So yes, the methodology I’ve used could be transferred to other medical conditions. And wouldn’t it be nice if all policy was informed by evidence and not just expert opinion?

In the driving seat: what’s the risk with epilepsy? takes place on Friday 14 September at 13.00 at Middleton Hall, University of Hull.

Book your tickets here.