Although HDL helps clear cholesterol from people's arteries, at very high levels, HDL's structure and actions change, and it can “harm health” in a variety of ways, the researchers wrote.
Over six years, they tracked 18,668 study participants, all 65 or older and physically and cognitively healthy at the start of the study. During those years, Cognitive dementia was detected in 850 participants (4.6 percent).
People with very high HDL levels are more likely to develop dementia than those with less optimal HDL levels. For example, older participants (75 or older) with high HDL levels were 42 percent more likely to develop dementia than those with normal HDL levels, and overall, anyone with high HDL levels had a 27 percent higher risk of developing dementia.
For adults only, An HDL level of 40 mg/dL or higher is considered healthy for men and 50 mg/dL or higher is considered a healthy level for women. For the study, a very high level of HDL was considered 80 mg/dL or higher.
The researchers wrote that the increased dementia risk from high HDL levels was independent of traditional dementia risk factors, including “physical activity level, alcohol intake, education, diabetes or smoking” and genetic influences.
The researchers pointed out that the reason for the link between high HDL levels and dementia risk is “not clear” and that further study is needed to explain the link.
This article is part of The Post's “Big Number” series, which takes a brief look at the statistical side of health problems. Additional information and related research are available through hyperlinks.