Is exercise to blame for Andrew Marr's stroke?

Much of the media is reporting on an interview given by broadcaster and journalist Andrew Marr, who is recovering from a stroke he had in January 2013.

In the interview, Marr explained that he had two 'mini-strokes' – or transient ischaemic attacks – the year before, but he "hadn't noticed".

Marr suggested that his stroke was triggered by vigorous exercise on a rowing machine, saying, "I'm frankly lucky to be alive".

But can exercise actually be bad for your health? It all depends on the type of exercise you are doing and your individual circumstances. It is worth noting that almost all of us can safely reduce our stroke risk through moderate exercise.

What are strokes and mini-strokes?

A stroke is a serious medical emergency where the supply of blood to the brain is disrupted. In over 80% of cases, strokes usually happen because a blood clot blocks the blood supply to the brain. They can also happen when a weakened blood vessel that supplies the brain bursts and causes brain damage, known as a haemorrhagic stroke.

From the account given in his interview, Andrew Marr could have had either an ischaemic or a haemorrhagic stroke: "I'd torn the carotid artery, which takes blood into the brain, and had a stroke overnight."

A mini-stroke, or transient ischaemic attack (TIA), is similar to a stroke but the symptoms only last a few minutes. Due to the short duration of symptoms, many people are unaware they have had a TIA, as was the case with Marr.

While not as serious as a stroke, a TIA is a serious warning sign that you need to make significant changes to your lifestyle or start taking medication, and usually both.

If left unaddressed, people who have had TIAs will often go on to have a full-blown stroke.

Is it unusual for men of Andrew Marr's age to have a stroke?

Strokes are uncommon, but certainly not rare in men in their fifties, like Andrew Marr. While the majority of strokes occur in over-65s, around one in four strokes occur in people under the age of 65.

The main risk factor for a haemorrhagic stroke is high blood pressure (hypertension) as the excess pressure can weaken the arteries in the brain and make them prone to splitting or rupturing.

In turn, risk factors for high blood pressure include:

• being overweight or obese
• smoking
• drinking excessive amounts of alcohol
• lack of exercise
• stress

Is Andrew Marr 'lucky to be alive'?

Yes. Even with prompt treatment a stroke can often be fatal. The fact that Andrew Marr left it until the next morning to seek treatment makes him extremely lucky to have lived to tell the tale.

Thankfully for Marr, he seems to be on the road to making a good recovery, although he has described difficulty walking. He does not appear to have developed the very serious after effects that often occur after a stroke, such as permanent physical disability and cognitive impairment.

Can exercise really cause a stroke?

Andrew Marr has described how he felt the symptoms of his stroke after he went on a rowing machine and "gave it everything I had". This, and other references to short bursts of intense exercise, suggests that he was undertaking some very vigorous exercise in the belief that this would benefit his health.

Most health advice actually focuses on simple, moderate levels of exercise, which raises the heart level and leaves you feeling slightly out of breath. Jogging, cycling and swimming are all good forms of moderate exercise. However, recent research has suggested that intense bursts of exercise may be just as good for you as the recommended 150 minutes per week of moderate exercise.

Almost everyone can safely take part in moderate exercise, and moderate exercise is one of the most effective and proven methods of reducing stroke risk. Just 30 minutes of moderate exercise five times a week can significantly reduce your risk of stroke.

Vigorous exercise is not safe or suitable for everyone. It is not usually recommended for people with a history of TIAs who have not received treatment to reduce their stroke risk.

If you have not been exercising regularly, it may be a good idea to first check with your GP that it is safe to take part in a course of vigorous exercise.

Despite the media emphasis on the stroke risk exercise could pose, it should also be borne in mind that Andrew Marr has said that he had been "heavily overworked". Stress is a known risk factor for high blood pressure, and it is possible that this may have played a part in his condition.

What do the experts say about Andrew Marr's stroke?

Nikki Hill, deputy director of communications for the Stroke Association, said: "We are delighted to see Mr Marr back on our screens. He's testimony to the recovery that is possible after stroke.

"Regular exercise is an important factor in stroke prevention and recovery. We have heard anecdotally that some activities like vigorous exercise can sometimes cause blood vessels to burst. We need more research on the underlying factors that might make that happen.

"We do know that high blood pressure itself is the single biggest cause of stroke. Until more research is done on specific triggers, we'd suggest getting your blood pressure checked and taking steps to keep it under control – exercise can help with that."

How can I reduce my stroke risk?

The best way of preventing a stroke is to eat a healthy diet, exercise regularly, avoid drinking too much and stop smoking.

It is never too late to take up exercise, eat more healthily, stop smoking or cut down on alcohol.

Read more about reducing your stroke risk.