Ebrahim S et al. (2006) Serum cholesterol, haemorrhagic stroke, ischaemic stroke, and myocardial infarction: Korean national health system prospective cohort study. BMJ 333: 22

The risk of ischemic stroke grows with increasing blood cholesterol level. It has been suggested, however, that lowering blood cholesterol level might increase the risk of hemorrhagic stroke. Ebrahim et al. have investigated the association of blood cholesterol level with stroke subtype in a cohort of 787,442 Korean civil servants (84% male).

Healthy participants were categorized to one of six groups on the basis of their cholesterol level. Between 1 August 1990 and 31 July 2001, 6,328 participants had an ischemic stroke, 3,947 had a hemorrhagic stroke, 3,170 had an undefined stroke, and 4,417 had a myocardial infarction. Risk of ischemic stroke and risk of myocardial infarction both grew with increasing serum cholesterol level (hazard ratios 1.20 and 1.48 per 1 mmol/l increase in serum cholesterol). Risk of hemorrhagic stroke decreased slightly with increasing serum cholesterol level (hazard ratio 0.91 per 1 mmol/l increase in serum cholesterol); this weak inverse association occurred only in patients with hypertension. Gamma glutamyl transferase level, which reflects alcohol consumption, was positively associated with hemorrhagic stroke risk. Increased hemorrhagic stroke risk in patients with low blood cholesterol levels occurred only in those who also had high levels of gamma glutamyl transferase.

The authors conclude that low blood cholesterol level might act as a marker of the damaging effects of alcohol, rather than being a cause of hemorrhagic stroke. They state that lowering cholesterol level to within the range likely to be achieved using statins is unlikely to increase the risk of hemorrhagic stroke.