Pollution 'is a leading global cause of strokes'

10th June 2016 - A new study has identified air pollution as a leading global risk factor for strokes.

The study, published in the health journal The Lancet Neurology says environmental and household air pollution accounted for almost a third of cases in 2013. However, it found that the majority of risk stemmed from factors that were in the power of individuals to change.

Experts say pollution is a much less important factor for strokes in the UK.

Stroke is the fourth single largest cause of death in the UK, and second in the world. Each year around 15 million people worldwide, and 152,000 people in the UK, experience a stroke.
 

The top 10 stroke risk factors worldwide

The latest study analysed stroke risk factors worldwide between 1990 and 2013.

It found the 10 leading stroke risk factors were:

1. High blood pressure
2. Eating too little fruit
3. High body mass index (BMI)
4. Too much salt in the diet
5. Smoking
6. Not eating enough vegetables
7. Environmental air pollution
8. Household air pollution from solid fuels
9. A diet low in wholegrains
10. High blood sugar levels.

The developed v developing worlds

In a statement, lead author Professor Valery Feigin, of Auckland University of Technology, New Zealand, says: "A striking finding of our study is the unexpectedly high proportion of stroke burden attributable to environmental air pollution, especially in developing countries.

"Smoking, poor diet and low physical activity are some of the major risk factors for stroke worldwide, suggesting that stroke is largely a disease caused by lifestyle risk factors. Controlling these risk factors could prevent about three-quarters of strokes worldwide."

The relative importance of different risk factors varied between regions and countries, and were also dependent on people's ages. For instance, household air pollution was a more important risk factor for stroke in central, eastern and western sub-Saharan Africa and south Asia, compared to Western Europe and North America.
 

UK risk factors

Dr Tim Chico, reader in cardiovascular medicine and consultant cardiologist at the University of Sheffield, explains that despite the focus on pollution, the "relative importance of this was much lower in Western Europe (and the UK) compared with less developed countries, in part because a lot of such air pollution comes from cooking over open fires using coal, wood, or dung".

He adds in a statement: "For me, the most relevant finding to the UK is that around 70% of strokes are associated with things that an individual can definitely address; smoking, low levels of physical activity, and poor diet (low in vegetables fruit, and wholegrains), and this is entirely consistent with lots of other studies."

Dr Patrick McSharry, a statistician at the University of Oxford, notes that the top 5 risk factors in the UK are:

1. High blood pressure (47.7%)
2. A high BMI (27.1%)
3. A diet low in fruit (25.1%)
4. A diet low in vegetables (23.1%)
5. Smoking (14.7%).

"A positive finding for policymakers is that 90% of the stroke burden is attributed to modifiable risk factors," he says. "This suggests that behaviour change strategies using taxation and education to promote a healthy diet and regular exercise could dramatically decrease the stroke burden in the UK."