File photo: Bosch

Oxford - You might think obeying the Highway Code and respecting speed limits makes you a good motorist. But your health and well-being could be compromising your safety behind the wheel without you realising.

“Driving requires our full concentration,” says Professor Russell Foster, a neuroscientist at Oxford University. “If there’s an underlying health issue, that can be seriously — and dangerously — compromised.

“Driving on a motorway can exacerbate the problem as it can be extremely monotonous, particularly if people are already tired.”

The RAC recently reported that one in 20 drivers unknowingly suffers from a sleeping disorder, sleep apnoea, that puts them at risk of nodding off at the wheel.

And if you have an accident and only discover afterwards it was caused by an underlying health issue, you may lose your licence or worse, says Paul Reddy, a solicitor and motoring law specialist at Slater & Gordon Lawyers. “It’s down to an individual to take responsibility for whether they are healthy enough to drive.”

Here, with the help of leading medical experts, we look at how your health might affect the way you drive...

Snorers can fall asleep on the road

One in 20 drivers unknowingly suffers from sleep apnoea syndrome, which might cause you to nod off at the wheel, according to research by the RAC. The organisation suggests that the disorder is responsible for up to one in five accidents.

It occurs when muscles in the throat relax as we go to sleep, reducing airflow and causing snoring, explains Professor Russell Foster, director of the Sleep and Circadian Neuroscience Institute at Oxford University.

“If the throat closes completely, you stop breathing for a couple of seconds, and the brain, realising it is being starved of oxygen, forces you to wake up,” he says. “This can happen up to 100 times a night — disrupting the sleep cycle and also causing you to miss out on phases of deep refreshing sleep. So you feel tired during the day.”

Many drivers are unaware they have the problem. Yet according to the RAC, those with undiagnosed sleep apnoea are six times more likely to have an accident.

See a GP if your partner complains you snore heavily and you have other warning signs such as a dry throat and headache on waking. Treatment involves using a continuous positive airway pressure (CPAP) device at night — this gently forces air into your airways while you sleep, preventing them closing.

A bad back may slow your braking

Any kind of lower back pain can make driving dangerous by weakening your leg muscles, says London-based chartered physiotherapist Sammy Margo.

“When there is a pinching in the spinal nerve, perhaps through inflammation or arthritis, this can cause referred weakness down the legs,” she adds.

“Drivers may not realise this until the leg is tested — perhaps by having to brake suddenly — and they may find that they can’t do it quickly.”

If you suffer from lower back pain, Ms Margo suggests driving with the seat forward so your leg doesn’t have to stretch to reach the pedal, and less effort is needed to brake quickly.

Heavy colds can halve concentration

Our concentration when driving with a bad cold or flu drops by more than 50 percent according to research from Cardiff University’s Common Cold Centre.

This is the equivalent of downing more than four double whiskies.

Car safety experts found reaction times dropped sharply and sudden braking became much more frequent as motorists with bad colds were less aware of surrounding traffic. They were also a third more likely to hit the kerb because they were less capable of judging distance.

...and medicine leaves you dangerously drowsy unfortunately, taking something to treat a cold or flu can also lead to road accidents since some preparations can cause drowsiness, says Professor Ron Eccles, director of Cardiff University’s Common Cold Centre. This may be down to anti-histamine, which controls runny noses and sneezing, but also has a sedative effect.

Another problem is if the medication contains codeine. It slows reaction times in many people and has been linked to low concentration levels and blurry eyesight — possibly because it causes the pupils to get smaller.

Research by website, in partnership with the Royal Pharmaceutical Society, found that one in seven motorists who has taken cold or flu medication containing codeine has suffered side-effects at the wheel.

If you are stopped by the police after taking a cold remedy, you could find yourself charged with ‘driving whilst unfit through drugs or alcohol’, which could lead to disqualification, says solicitor Paul Reddy. Professor Eccles warns: “I wouldn’t drive for at least six hours after taking one of these preparations.”

An eye condition makes wing mirrors useless

Last year, an estimated 2,000 drivers in the UK were involved in road crashes due to poor vision, according to the College of Optometrists. One reason, they say, is that motorists may not realise their eyesight has deteriorated because of glaucoma. This is where the drainage tubes in the eye become blocked, preventing the aqueous humour — the fluid that creates pressure in the eye to keep its shape — from draining properly.

The condition affects the peripheral vision, says optometrist Dr Rob Hogan of iCare Consulting. “So, when driving, you may well miss anything that comes into your side vision — for example, anything you would see in your wing mirror, such as a cyclist — as you’d just have a black spot.

“Any damage caused by glaucoma can’t be repaired, which is why an early diagnosis is so important.”

Treatment involves medication, eye drops, and laser surgery to clear the blocked tubes.

Why you should keep Jelly Babies handy

Plunging blood sugar levels can be a serious hazard. Known as reactive hypoglycemia, it can suddenly make you feel shivery and cause a tingling around your lips and a deep, painful hunger, which can all be a major distraction.

There is no clear cause — it just seems to randomly affect some people, usually around four hours after having a heavy meal as the body seems unable to sustain blood sugar levels, says Dr Stephen Lawrence, a GP and medical adviser to Diabetes UK.

If this happens to you, see your GP about an HbA1C blood test — a more sophisticated analysis of the blood — to rule out diabetes. Have a snack before you hit the road, and take a packet of Jelly Babies with you as these release glucose quickly into the blood.

Getting caught short makes you speed

The risk for people with urge incontinence — which causes an urgent feeling to go — is that they get caught short and “end up speeding to make it to their destination or the nearest rest stop,” says Chris Eden, professor of urology at Surrey University.

“A serious urge to urinate can happen even if you went a short time before,” he warns.

Urge incontinence is caused by faulty nerve signals, which trigger small bladder contractions, meaning messages go to the brain telling it the bladder needs to empty.

The condition can be treated with medication that relaxes the bladder. Pelvic floor exercises can also help.

You can drive blind for 15 metres when you sneeze

An increasing number of adults are developing hay fever for the first time. Possible causes include new species of exotic plants, serious infections or moving to a more polluted area.

These adults may suddenly find themselves sneezing uncontrollably — and as we tend to close our eyes when we sneeze, this can make driving a hazard.

Around two million UK motorists have either had an accident, a near miss or have temporarily lost control of their car by sneezing at the wheel, according to insurance firm Esure. It’s most hazardous on the motorway, as drivers can travel up to 15 metres with their eyes closed during a sneeze.

Stephen Foster, a Kent-based pharmacist and allergy specialist, suggests vacuuming your car regularly and cleaning surfaces with a damp cloth to keep it free of dust and pollen, as well as getting air-conditioning checked annually.

“Use a nasal steroid spray such as Beconase or take a non-sedative antihistamine such as Benadryl before you get into the car,” says Mr Foster. “Check with your pharmacist that anything you buy won’t cause drowsiness. And keep the windows closed while driving.”

Rubbing a balm such as HayMax around your nose can help as this traps pollen.

Sleeping pills give you a hangover

Insomnia pills — such as over-the-counter remedies like Nytol — can have a hangover effect for several hours the next day, as in some people it may take this long for the liver to expel the drugs from the body.

“They also prevent you going into a deep, ‘slow-wave’ sleep during the night, which is why you may not feel refreshed in the morning,” adds Professor Foster. “Avoid sleeping pills if you are doing a long drive the next day.”