High total cholesterol may be risk factor for ischemic stroke
Japanese men with high serum total cholesterol levels have an “excess” risk for stroke, report researchers.
Hiroyasu Iso (Osaka University Graduate School of Medicine, Japan) and team found that men with total cholesterol levels of 6.21 mmol/L (high; 239.77 mg/dL) or above had a 1.7-fold higher risk for ischemic stroke than those with levels below 4.65 mmol/L (low; 179.54 mg/dL).
“High serum total cholesterol levels represent a risk factor of ischemic stroke in Western countries,” they explain. “However, this association has not been thoroughly investigated in Asian populations where the incidence of stroke is high.”
To address this, Iso and co-investigators performed a 12-year follow-up study involving 11,727 men and 21,742 women, aged 40-69 years, who were free of cardiovascular disease and cancer at baseline.
Overall, 612 ischemic strokes (293 lacunar infarctions, 107 large-artery occlusive infarctions, and 168 embolic infarctions) were reported.
The risk for stroke and large-artery occlusive infarction was a significant 1.63- and 2.86-fold higher among men with high total cholesterol levels compared with those with low levels, writes the team. But women did not show such associations.
Total Cholesterol, Severity of Stroke, and All-Cause Mortality
The association of blood cholesterol with the risk of stroke, a very important clinical and public health issue, appears to be in dispute. To fuel the debate, Olsen et al reported a study of 513 patients admitted in a Copenhagen, Denmark hospital with acute ischemic stroke. All study data, including measures of total serum cholesterol (TSC) and the severity of stroke, were collected on admission in the hospital, and poststroke 10-year all-cause mortality was ascertained. The severity of stroke was measured by the Scandinavian Stroke Scale that is based on a composite of neurological deficits, and severity was found to be correlated with the cerebral infarct size seen on CT scans. The authors found that poststroke TSC levels were inversely associated with the severity of stroke, cerebral infarct size, and mortality, which were adjusted for the covariates.
The authors concluded that “hypercholesterolemia primarily is associated with minor strokes due to small-vessel occlusion”. Their conclusion contradicts the well established role of cholesterol in the pathogenesis of atherosclerosis including that of cerebral and precerebral vessels. Ischemic stroke is predominantly caused by macrovascular disease, not microvascular. The findings of this study are unreliable and misleading simply because poststroke TSC levels are not representative of the levels before the onset of the arterial disease. Cross-sectional data cannot establish the temporal relationship between TSC and the risk of severe ischemic stroke. Only measures of TSC in apparently healthy subjects should be used to determine the effect of cholesterol on the risk of ischemic stroke, its severity and associated mortality.
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Kazim Sheikh, MD
Furthermore, each 1 mmol/L increment in total cholesterol was associated with a 14% and 30% increase in the risk for stroke and large-artery occlusive infarction, respectively.
“This report constitutes the first evidence of the excess risk for ischemic stroke for men with high serum total cholesterol levels in an Asian population,” write Iso et al in Atherosclerosis.