Increasing Total Cholesterol Less Worrisome for Cognition in Old Age

As people grow older, the relationship between high cholesterol and cognitive decline weakens and, in fact, may even reverse at age 85, a new study shows.

Among individuals participating in the Framingham Heart Study who reached the age of 85 without impaired cognitive function, those with an increase in total cholesterol over the past four decades had a lower risk of subsequent cognitive decline, Jeremy Silverman, PhD, and James Schmeidler, PhD (Icahn School of Medicine at Mount Sinai, New York, NY), report in a study published online March 4, 2018, ahead of print in Alzheimer’s & Dementia.

The findings, Silverman told TCTMD, provide support for what he and his colleagues have dubbed the “protected survivor model.” According to that concept, there is a small subset of the population inherently protected against certain risk factors—high cholesterol, for instance—that is more likely to survive to old age.

“Once you’re dealing with 85-year-olds who are cognitively still doing very well, you’re dealing with a group that is very unrepresentative from the original birth cohort and the likelihood that that small group of people for whom cholesterol did not have a deleterious effect on cognition is now a much bigger proportion of the remaining survivors,” Silverman explained.

He said this study could help refine research looking into what factors—genetic or otherwise—are associated with successful cognitive aging. Future studies could, for example, compare a cohort of “protected survivors” with a cohort of individuals with dementia and high cholesterol levels to explore differences between the two.

Silverman also cautioned against reading too much into the findings in terms of a clinical message.

“We’re certainly not suggesting that people actively try to raise their cholesterol when they get to be 85. We don’t think that’s likely to have any effect, and [it] could be bad if you’re not among the protected group,” he said. “But it does suggest that at those ages one need not be as concerned about what levels you have had or what levels you currently have. At least insofar as one is concerned about cognitive problems, having a high cholesterol at very late ages doesn’t seem to be something that you need to worry about as far as your risk going forward.”

We’re certainly not suggesting that people actively try to raise their cholesterol when they get to be 85. Jeremy Silverman

For the study, Silverman and Schmeidler looked at data on 1,897 participants of the Framingham Heart Study who had intact cognition at baseline (mean age at entry 40.2 years). They were followed for marked cognitive decline, defined as a deterioration from intact cognition to dementia or a Mini-Mental State Examination (MMSE) score of 20 or lower. During follow-up, 6% were diagnosed with dementia and 10.6% scored low on the MMSE.

The investigators found that low entry age, lower levels of education, nonuse of statins, and an increase in total cholesterol over time were all associated with a greater risk of marked cognitive decline across the entire cohort. Those relationships, however, grew weaker as the age at which the cognitive assessments were performed increased.

Silverman and Schmeidler also looked at two specific age groups: 75 to 84 and 85 to 94. In the former, none of the factors were associated with risk of marked cognitive decline. In the older group, however, both an increase in total cholesterol from midlife and a high measurement at midlife were associated with a lower risk of cognitive decline.

“So if you’re still in good cognitive health at 85 and above, it looks like having had a high cholesterol in midlife is actually associated with a better outcome than having had a normal cholesterol level,” Silverman said.