Background and purpose: Epidemiological studies have found no relationship between total cholesterol and stroke risk, but little attention has been paid to high-density lipoprotein-cholesterol (HDL-C).
Methods: We performed a systematic PubMed literature search for epidemiological studies that examined the association between HDL-C level and stroke or carotid intima-media thickness (IMT).
Results: We identified 18 studies on the relationship between HDL-C and stroke risk and 37 on HDL-C and carotid IMT. Eight of ten prospective cohort studies (n=238,739) and three of eight case-control studies (n=3604 cases, 8220 controls) supported an association between elevated HDL-C level and decreased risk of stroke. Prospective cohort studies reporting on relative risk per unit increase in HDL-C showed an 11-15% decreased stroke risk per 10-mg/dl increase in HDL-C. Of 37 studies on carotid IMT, 31 reported cross-sectional, one longitudinal, and five both cross-sectional and longitudinal associations between HDL-C level and carotid IMT. Of 36 cross-sectional studies (n=51,288), 20 showed an inverse association between HDL-C level and carotid IMT. Of six longitudinal studies (n=20,065), three showed no association, one showed a weak association in a subgroup of white women and two showed a significant inverse relationship between HDL-C level and carotid IMT. Pooled estimates could not be calculated because of the variation in study designs and analysis.
Conclusions: The weight of evidence in the literature supports an inverse association between HDL-C level and stroke or carotid atherosclerosis, but more data are needed to firmly establish this protective effect.