How levels of ‘good' cholesterol may increase dementia risk

So-called “good” HDL cholesterol may not be as healthy as experts once thought, a new study suggests. 

The new study, published Wednesday in Neurology, found that having either high or low levels of high-density lipoprotein, or HDL, cholesterol, may increase the risk of dementia in older adults. It’s more evidence showing that keeping HDL cholesterol within a certain range is important for cardiovascular and brain health.  

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“The relationship between HDL cholesterol and dementia is more complex than we previously thought," said the study’s lead author, Erin Ferguson, a doctoral student studying epidemiology at the University of California San Francisco. "While the magnitude of this relationship is relatively small, it’s important,”

The results show a correlation between HDL cholesterol and dementia, but do not prove that low or high levels of the lipid directly caused dementia. The study, which was supported by the National Institute on Aging and the National Institutes of Health, included more than 184,000 adults with an average age of 70. None had dementia when the study began. Researchers used a combination of surveys and electronic records from the Kaiser Permanente Northern California health plan to track cholesterol levels, health behaviors and whether someone developed dementia over about 13 years. During that time, just more than 25,000 people developed dementia. 

The Centers for Disease Control and Prevention recommends people keep their total cholesterol at about 150 mg/dL, or milligrams per deciliter of blood, with LDL at or below 100 mg/dL. Low-density lipoprotein, or LDL, cholesterol, has long been recognized for its often deadly impact on the cardiovascular system. 

Read the full story on NBCNews.com here.