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Published on: June 18, 2021
Cholesterol as a Risk Factor for Subarachnoid Hemorrhage: A Systematic Review
Joni Valdemar Lindbohm1,2, Jaakko Kaprio1,3,4, Miikka Korja2
1Department of Public Health, University of Helsinki, P.O. Box 41, FI-00014, Helsinki, Finland.
Insights
High total cholesterol (TC) increases the risk of subarachnoid hemorrhage (SAH) in men, according to low-bias studies. Hypercholesterolemia
Area of Science:
- Neurology
- Cardiovascular Science
- Epidemiology
Background:
- The association between total cholesterol (TC) and subarachnoid hemorrhage (SAH) risk is debated, with conflicting reports on whether high or low TC poses a greater risk.
- Existing research presents inconsistencies, necessitating a comprehensive review to clarify the role of lipid profiles in SAH etiology.
Purpose of the Study:
- To systematically review and synthesize evidence clarifying the association between lipid profiles, specifically total cholesterol (TC), and the risk of subarachnoid hemorrhage (SAH).
Main Methods:
- A systematic literature search was conducted across major databases (PubMed, Scopus, Cochrane Library) without limitations on publication details.
- Risk of bias was assessed using established guidelines (CASP, Cochrane Collaboration), and data were analyzed using a random effects model with heterogeneity assessed via I2-statistics.
- Due to significant heterogeneity, a qualitative analysis was prioritized, focusing on studies with a low risk of bias.
Main Results:
- Twenty-one studies were included, with a majority assessing TC and a minority evaluating HDL; LDL was not assessed in relation to SAH risk.
- High heterogeneity was observed across study types and subgroups, prompting a focus on qualitative findings from low-risk-of-bias studies.
- Two low-risk-of-bias studies indicated that elevated TC levels are associated with increased SAH risk in men, while the impact of HDL remained uncertain.
Conclusions:
- Elevated total cholesterol (TC) is suggested as a risk factor for subarachnoid hemorrhage (SAH) in men, based on high-quality evidence.
- The population attributable risk of hypercholesterolemia may be substantial in men, potentially surpassing that of smoking and hypertension.
- The risk factor profile for SAH in men, excluding diabetes and obesity, appears similar to other cerebrovascular diseases.
Background:
The role played by total cholesterol (TC) in risk for subarachnoid hemorrhage (SAH) is unclear because studies report both high and low TC each as a risk factor. We performed a systematic review to clarify associations between lipid profile and SAH.
Methods:
Our literature search comprised Pubmed, Scopus, and Cochrane Library databases with no language, publication year, or study type limitations. The Preferred Reporting Items for Systematic reviews and Meta-analyses (PRISMA) checklist guided our reporting. Data forms adapted from the Critical Appraisal Skills Program (CASP), and Cochrane Collaboration guidelines provided a platform for risk-of-bias evaluation. We used a random effects model to calculate pooled estimates and assessed heterogeneity with I2-statistics.
Results:
Of the final 21 studies reviewed, 12 were prospective and 9 retrospective. All studies assessed TC, four assessed HDL, and none LDL in risk for SAH. Heterogeneity among all, retrospective, and Asian studies was high (I2 = 79.5%, I2 = 89.0%, and I2 = 84.3%) and considerable in prospective (I2 = 46.0%). We therefore focused on qualitative analysis and found that only two studies had a low risk of bias. According to these studies high TC increases risk for SAH in men, whereas the role of HDL remained unclear.
Conclusion:
The low-risk-of-bias studies suggest that elevated TC levels elevate risk for SAH in men. Due to the high prevalence of hypercholesterolemia, population attributable risk (PAR) of hypercholesterolemia may exceed the PARs of smoking and hypertension in men. Apart from diabetes and obesity, the risk-factor profile of SAH seems to resemble that of other cerebrovascular diseases, at least in men.
