Certain health issues, such as vision problems, can significantly impact driving and should never be concealed from the DVLA.
However, there are also a range of other conditions that could affect a person's behaviour on the road, and failing to inform the department about these could result in hefty fines.
This includes several sleep disorders, which sufferers must report to the DVLA if they have been diagnosed with one. One of the main concerns is narcolepsy, a disruptive sleep condition that leads to excessive daytime sleepiness, reports Wales Online.
Narcolepsy is often depicted in popular media due to its symptoms, where sufferers experience uncontrollable episodes of falling asleep, sometimes without much warning.