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Smoking and Stroke Risk
(Wednesday, 21st May 2003)

Smoking increases the risk of all forms of stroke (REF: Stroke)

Paper reviewed by Clinnix medical consultant Dr Hugh Bethell.

Cigarette smoking is a well-established risk factor for ischaemic stroke and subarachnoid haemorrhage (SAH) but there is uncertainty about the role of tobacco in intracerebral haemorrhage (ICH). This study shows that smoking does play an important part in the aetiology of ICH.

The study looked at the incidence of, and risk factors for, stroke in the US-based Physicians' Health Study, which included 22,067 apparently healthy male physicians. During 17.8 years of follow-up, involving 385,419 person-years, a total of 1,069 strokes occurred, of which 139 were haemorrhagic (108 ICH, 31 SAH), 913 were ischaemic and 17 were undefined. 49.6% of the cohort reported having never smoked, 39.4% reported past smoking, 3.9% reported current smoking <20 cigarettes/day and 7.1% reported smoking 20 or more/day.

The correlations between smoking and stroke were:

• Compared with non-smokers, ex-smokers had no increase in risk of haemorrhagic stroke - neither ICH or SAH
• For smokers of less than 20/day, the relative risk (RR) for haemorrhagic stroke was 1.65 - 1.6 for ICH, and 1.8 for SAH
• For smokers of 20 or more/day, the RR of haemorrhagic stroke was 2.36 - 2.1 for ICH, and 3.2 for SAH
• Compared to never-smokers, the RRs for ischaemic stroke were 0.99 for ex-smokers, 1.56 for smokers of less than 20/day and 2.25 for smokers of 20 or more/day.

Haemorrhagic stroke accounts for about 20% of all strokes and the incidence of ICH is about twice that of SAH. ICH has a mortality of 40 to 50% and carries a high prevalence of long-term disability. The results confirm that cigarette smoking is an important risk factor for this dangerous condition, with a graded increase in risk with increasing cigarette intake.

As the authors of this study report, 'The effect of smoking on ICH is of about the same magnitude as the effect of smoking on ischaemic stroke. These results add to the multiple health benefits that can be accrued by abstaining from cigarette smoking.'

REF: Kurth T et al. Smoking and the risk of haemorrhagic stroke in men. Stroke 2003; 34: 1151-5

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