NEW YORK, Oct 5, (Agencies): A recent study challenges the conventional wisdom about the health benefits of "good cholesterol," suggesting that high-density lipoprotein (HDL) may not be as beneficial for older individuals as previously thought. Published in the journal Neurology, this study reveals a potential link between both high and low levels of HDL and an increased risk of dementia among elderly people.

Researchers conducted a comprehensive investigation involving over 180,000 California residents. The study spanned approximately two years, commencing between 2002 and 2007, followed by an average of nine years of monitoring through medical records. The participants in this study now have an average age of 70 years.

Maria Glymour, the study's lead author, emphasized the significance of their research, stating, "Previous studies on this topic have been inconclusive, and this study is especially informative because of the large number of participants and long follow-up." She further explained, "This information allowed us to study the links with dementia across the range of cholesterol levels and achieve precise estimates even for people with cholesterol levels that are quite high or quite low."

During the study period, approximately 25,000 individuals developed dementia. Surprisingly, those with the highest levels of HDL cholesterol exhibited a 15 percent higher dementia rate compared to those in the middle range. Conversely, individuals with the lowest HDL levels experienced a 7 percent higher dementia rate when compared to their middle-range counterparts.

It's worth noting that the recommended "healthy" HDL level is 40 mg/dL in the blood, while the study participants had an average of about 54 mg/dL. The study also investigated low-density lipoprotein (LDL), often referred to as "bad cholesterol," but found no significant association between LDL cholesterol and dementia rates.

Glymour clarified the implications of their findings, saying, "The elevation in dementia risk with both high and low levels of HDL cholesterol was unexpected, but these increases are small, and their clinical significance is uncertain." She added, "In contrast, we found no association between LDL cholesterol and dementia risk in the overall study cohort. Our results add to evidence that HDL cholesterol has similarly complex associations with dementia as with heart disease and cancer."

This study, released recently, complements the findings from another study in July, which highlighted the potential risks associated with fluctuating cholesterol levels. The earlier study, also published in Neurology, indicated that individuals with the most fluctuating cholesterol levels faced a 19 percent higher risk of developing dementia.