July 10 (UPI) -- Older adults with higher levels of a specific protein in their blood have better cognitive function and might be at lower risk for dementia than those with lower levels, a study published Friday by JAMA Network Open has found.
The protein, apolipoprotein E, is found in high-density lipoprotein, or HDL, which also is known as "good cholesterol," according to researchers at Harvard University, the University of Florida, University of Pittsburgh and University of Washington.
Its benefits are only seen when HDL does not contain another protein called apolipoprotein C3, which has been linked with heart disease, the researchers said.
"Lower apolipoprotein E in [blood] is a known risk factor for dementia, but the underlying biological mechanisms are not fully understood," study co-author Manja Koch, a research associate in the Department of Nutrition at Harvard T.H. Chan School of Public Health, told UPI.
Ultimately, the findings could help shape "lifestyle"-based treatments -- like changes to diet and exercise -- to slow or prevent dementia progression and help doctors identify older adults at risk for decline in cognitive function, Koch said.
Earlier research has indicated that apolipoprotein E has a "cardioprotective" effect, meaning it may help prevent the development of heart disease, according to lead author Majken K. Jensen, an adjunct professor of nutrition at Harvard T.H. Chan.
Apolipoprotein C3 has been linked with the development of atherosclerosis, a narrowing of the arteries, which is a precursor for heart disease, she said.
For this study, Jensen, Koch and colleagues measured levels of apolipoprotein E and apolipoprotein C in nearly 1,400 older adults between 76 and 81 years old. They monitored study participants for roughly six years, they said.
Participants with higher apolipoprotein E in HDL with no apolipoprotein C3 were 14 percent less likely to develop dementia, according to the researchers.
However, participants with elevated apolipoprotein E in good cholesterol containing apolipoprotein C did not have a reduced risk for developing dementia, they said.
About 6 million Americans are living with some form of dementia, according to the Alzheimer's Association.
"Our findings warrant further investigation and at present cannot be directly translated into clinical practice," said Jensen, who is also professor of public health at the University of Copenhagen in Denmark.
"However, we think that a better understanding of the mechanisms of dementia will have value for dementia prevention."