Possible Link Between HDL Levels and Dementia Risk in Older Individuals Sheds New Light on the Role of 'Good' Cholesterol

New research reveals that both high and low levels of high-density lipoprotein (HDL), also known as good cholesterol, are linked to an increased risk of dementia. Unlike previous studies, this research factored in the influence of statin medications and delved into potential intricate associations. The researchers analyzed a wealth of data from surveys and electronic health records to uncover these relationships.

Longitudinal Study Tracked Cholesterol Levels of California Residents

This study, titled "Low- and High-Density Lipoprotein Cholesterol and Dementia Risk Over 17 Years of Follow-up Among Members of a Large Health Care Plan" published in the journal Neurology, spanned over 17 years and involved more than 184,000 California residents with an average age of 70.

It sought to investigate the relationship between HDL-C, LDL-C, and dementia risk in older individuals. Participants were asked to complete health surveys, commencing between 2002 and 2007, followed by monitoring their medical records for an average of nine years.

Maria Glymour, the study's author, emphasized the significance of this research, highlighting the inconclusiveness of previous studies on this topic. The substantial participant count and the extended follow-up period allowed for a comprehensive examination of the links between cholesterol levels and dementia across the spectrum, including individuals with both high and low cholesterol levels.

The study cohort consisted of members of the Kaiser Permanente Northern California health plan, aged 55 or older. These individuals did not have dementia before the survey and had their cholesterol levels measured within two years after participating in the survey.

The researchers continued to monitor this cohort until December 2020 to observe any instances of dementia. They applied meticulous data analysis methods and models, considering various factors such as demographics and medications. The study findings revealed that both very low and very high levels of HDL-C were associated with a heightened risk of developing dementia.

Link Between Good Cholesterol and Bad Cholesterol

The study's results unveiled significant findings regarding the relationship between cholesterol levels and dementia risk. Individuals with the highest HDL cholesterol levels showed a 15% elevated risk of dementia compared to those with mid-range HDL levels, while those with the lowest HDL levels exhibited a 7% heightened risk in contrast to the mid-range group.

Remarkably, these associations retained their significance even after accounting for various factors like alcohol consumption, hypertension, cardiovascular disease, and diabetes.

In contrast, there wasn't a clear-cut link between "bad" LDL-C cholesterol levels and dementia risk observed in the entire participant group. However, among individuals using statins, higher LDL-C levels were mildly associated with an increased dementia risk.

Intriguingly, age seemed to have an impact on the relationship between HDL-C and dementia risk, but it did not appear to influence the link between LDL-C and dementia.

While the study established associations between cholesterol levels and dementia risk, it did not confirm a direct causal link between high or low HDL cholesterol and dementia. Lead study author Erin Ferguson noted a U-shaped relationship between HDL-C and dementia risk, suggesting that individuals with either lower or higher HDL-C levels had a slightly elevated dementia risk.

However, no significant connection between LDL-C and dementia risk was found. Neurologist Clifford Segil praised research focused on dementia prevention, especially considering the limited advancements in dementia treatments in 2023.

This study aimed to use cholesterol-lowering medications to reduce the overall risk of dementia rather than specifically targeting statin use for preventing multi-infarct or vascular dementia.

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