Hyperlipidemia and the Aging Brain: The Impact of High Cholesterol on Cognitive Decline among the Aging Population

Introduction: Dementia is a collective term for a number of neurodegenerative diseases characterized by cognitive impairment, memory loss, imparied judgement, and personality changes. There is currently no known cure and current treatment is focused mainly on symptomatic relief. Therefore, an intervention that can reduce the risk of dementia can have a major public health impact. This review aims to examine the current literature on cardiovascular health, specifically hyperlipidemia, and whether such a condition increases the risk of developing dementia in those ages 65 to 85. Methods: A literature search was performed in November 2019 through PubMed, ScienceDirect and Google Scholar. Six articles consisting of randomized control trials (RCTs) and cohort studies were selected based on publication date and sample population. The results of these articles were then analyzed and compared. Results: Overall, five out of six studies found significant relationships between high cholesterol and cognitive decline. Three studies examined the impact of cholesterol-lowering drugs on Alzheimer’s Disease (AD) pathogenesis, two specifically explored the impact of dietary cholesterol, and one looked at atherosclerosis as a result of high cholesterol on the development of dementia. Five studies found a significant relationship between high cholesterol and cognitive decline, and two found ApoE to be a mediator of the relationship. Due to several limitations within the studies, the collective evidence is not strong enough to confirm a relationship between high cholesterol and cognitive decline. Discussion: Significant results were found in five out of six articles. However, there were several limitations that prevent the findings from reaching clinical significance. These include the lack of standardization among the variables in the studies, small sample sizes, a lack of blinding, and insufficient timelines and follow-up. All such factors enable the introduction of bias that weakens internal validity and hinders the ability to draw strong conclusions. Conclusion: The aging population and high prevalence of both dementia and hyperlipidemia among adults in the US highlight the need to explore a potential relationship between cardiovascular health and cognitive decline. Given the shortcomings of the various studies, few recommendations can be made regarding changes to clinical practice. However, the findings contribute to a greater knowledge base on the complex interplay between cholesterol, cognitive decline and related brain changes. Future studies are warranted to further investigate this relationship, develop more robust conclusions, and hopefully reduce the burden of disease on the aging population