The Harvard University team looked at records of more than 16,000 people. The American Journal of Preventative Medicine study found the risk rose by up to 72% for some non-smokers. The stroke dangers to smokers are well known, but there are fewer studies which have explored the risk from passive smoking. Since the introduction of smoking bans in public places across the UK, the home is now the most likely place for non-smokers to breathe second-hand smoke.

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