Summary: A new study shows that a decline in total cholesterol may be associated with the early stages of dementia. More research is needed to understand what this means.
When Dad was in his mid-60’s, the results of his annual physicals were straight out of an advertisement about healthy aging. His weight and blood sugar were normal, and his blood pressure and cholesterol were low.
Now it seems Dad’s low cholesterol levels weren’t such a good sign after all. Some research links high cholesterol in mid-life to increased risk of heart problems and dementia. But later in life, low cholesterol levels, not high, are linked to increased risk of dementia and even death.
A new study, published in the Archives of Neurology, shows that a decline in total cholesterol may be associated with the early stages of dementia. Researchers at King’s College London Institute of Psychiatry looked at 26 years of total cholesterol readings for over 1000 Japanese American men participating in the Honolulu-Asia Aging study. They found that “cholesterol levels in men with dementia, and, in particular, those with Alzheimer disease had declined at least 15 years before the diagnosis and remained lower than cholesterol levels in men without dementia throughout that period.”
What do the results of this study mean? I fired off a list of questions to the study’s lead author, Dr. Robert Stewart, Head of Section of Epidemiology at the Institute of Psychiatry at King’s College.
Q: Should Dad have been worried about his low cholesterol readings? Could the drop in cholesterol seen in the new study be a “biomarker” for Alzheimer’s or dementia?
Dr. Stewart: This is a possibility. However, the drop in cholesterol in our study occurred quite a long time before the onset of dementia and so you would have to wait a long time to know if such a ‘biomarker’ was accurate. This is a finding that needs further investigation.
Q: Did the men in the Honolulu-Asia Aging Study who developed dementia have high cholesterol levels at the beginning of study?
Dr. Stewart: The analysis was designed to measure change in cholesterol over time, so it’s not strictly possible to comment on differences in initial levels. There have been a few studies which have suggested that high cholesterol levels in middle age may predict a higher risk of developing dementia later on in life, but this is still a slightly controversial issue.
Q: Is a drop in cholesterol an underlying cause of dementia and death, or simply a sign of some disease process such as heart disease or a disease process in the brain?
Dr. Stewart: We really can't be sure what it was due to. In the paper we mention that a drop in cholesterol can be caused by an inflammatory event or possibly a nutritional deficit, but you are right in that it could be secondary to cardiovascular disease or secondary to some early brain change. We simply don't know and need to investigate this issue further.
Q: Finally, what does this study say about the potential use of statins to treat dementia?
Dr. Stewart: I don't think that our findings have any particular implication for statin trials. It is likely that the drop in cholesterol in our study was secondary to other processes and was not a direct cause of later dementia. It is also highly unlikely that it was related to cholesterol lowering treatment as these medications were not widely available at the early stages of this study when the cholesterol decline occurred.
We may never know whether Dad’s low cholesterol was a bad sign, or whether taking Mevacor affected his dementia. With the ongoing studies on the use of statins to treat Alzheimer’s, and further research into late-life drops in cholesterol, we should have a better picture of the relationship between cholesterol and dementia in the next few years.