Smoking as a risk factor for cortical ischaemia presumably due to carotid occlusive disease

Smoking is now a well established risk factor for ischaemic stroke. However, the risk associated with smoking may differ between subgroups of ischaemic stroke. To test the hypothesis that cortical ischaemia due to carotid artery occlusive disease, the latter of which has previously been linked to smoking, may have a higher smoking risk compared to other forms of cerebral ischaemia, we identified 178 cases of cortical ischaemia presumably due to carotid occlusive disease in our previous case-control population and compared the odds ratios (OR) for smoking risk in this group with that in group of 244 cases of other forms of cerebral ischaemia combined. All cases were individually matched for age (+/- 5 years) and sex with neighbourhood controls. Multiple conditional logistic regression was used to adjust for potentially confounding factors. The OR for current smokers in the cortical group was higher than that in the non-cortical group [OR 4.4, 95% confidence interval 2.2, 8.9 vs. 2.1 (1.1, 4.1)], particularly for those who smoked more than 60 pack-years [5.5 (2.2, 14.0) vs. 1.5 (0.6, 3.8)] and those who currently smoked more than one pack per day [20.2 (3.3, 122.3) vs. 2.6 (0.8, 8.2)], but not significantly. Overall, there is some evidence to suggest that smoking may be a more potent risk factor for cortical than for other forms of cerebral ischaemia, particularly at high smoking rates. Further studies are needed to substantiate this finding.