Do statins (cholesterol meds) reduce cognitive decline in Alzheimer's patients?
A look at new evidence from Sweden
An open-access study was just published in Alzheimer’s Research and Therapy, giving evidence that statins (cholesterol-reducing medications) can actually reduce cognitive decline in Alzheimer’s patients.
How does it work?
The concept behind this slowing of Alzheimer’s disease progression is that excess cholesterol in the brain may be part of the problem for Alzheimer’s patients. According to prior research cited by the authors of this study, excess cholesterol could (a) impede blood flow in the brain and (b) increase the build-up of harmful amyloid plaques. If so, reducing brain cholesterol should, in theory, help reduce Alzheimer’s symptoms.
What is the evidence?
The study looked at a dataset of 15,568 Swedish patients with Alzheimer’s disease or mixed dementia and hyperlipidemia (elevated cholesterol and triglycerides), two-thirds of whom were on statin medication. The analysis showed that taking statins on a daily basis was associated with 0.63 more points on the MMSE (Mini-Mental State Examination) after 3 years compared to not using statins.
Note that a correlational study of Humana insurance claims data also showed a reduction in the incidence of neurodegenerative diseases like Alzheimer’s in statin users.
A few cautions
According to one of the authors of the paper, this result doesn’t mean doctors should start prescribing statins for dementia, but they shouldn’t let a dementia diagnosis stop them from prescribing statins. The difference in cognitive decline between statin users and non-users (.21 points per year) does not reach a clinically meaningful threshold (1 to 3 points per year) that scientists tend to want to see before recommending physicians prescribe medications.
Every study has limitations. One prominent limitation of this study is that it is correlational, meaning that they can’t infer causality the way they could in an experiment where neither researchers nor participants know who is in the placebo or treatment groups. We can see from this study that statin use and decreased cognitive decline co-occur, but we can’t know for sure why that is. A 2015 article explained the problem of inferring causality from correlational research better than I can. A second limitation is that the study's outcome depends on a series of statistical choices by the authors. This is always the case with large survey datasets, and it helps explain why scientists often come to different conclusions with the same or similar data. Consider, for example, that scientists have been going back and forth for years about whether statins help or hurt Parkinson’s patients (another neurodegenerative disease), and to this day, there is no solid consensus.
None of this is meant to say the study is bad. I’m only saying that I agree with the authors that more research in this area is needed. This is a great early step.
About the author
Aaron Charlton, PhD is a health, medical and science blogger who works for Neurology Associates Neuroscience Center and other medical clients.
Very interesting correlation. Statins also seem to reduce PSA levels, is it a miracle drug??