A new peer-reviewed study shows that some drugs, including vaccines, seem to lower the risk of developing dementia, including Alzheimer’s disease. Scientists may know why this happens.

There’s currently no cure for dementia. Although some recently developed drugs show promise in slowing the progress of the disease, these drugs are costly. They may only have limited benefits for many dementia and Alzheimer’s disease patients.

As I have written previously, vaccines seem to be linked to a lower risk of dementia and Alzheimer’s disease. This new study shows that some other drugs can have the same effect.

This post will examine this new study and show the mechanism of how these drugs and vaccines might reduce the risk of dementia.

What are Alzheimer’s disease and dementia?

Before I proceed, it’s important to describe Alzheimer’s disease (AD). It is a chronic neurodegenerative disease that usually starts slowly and worsens over time. It accounts for 60-70% of dementia cases, even though the terms are sometimes used interchangeably. Alzheimer’s disease is a form of dementia.

Amyloid plaques, phosphorylated tau tangles, and neurofibrillary tangles are generally easily visible pathologies that can be observed by microscopic analysis of brain tissue from autopsies of those potentially afflicted by AD. These plaques and tangles seem to affect nerve functioning. Despite these observations, the precise pathophysiology, or development, of the disease is not known.

Since amyloid plaques are often identified in patients with Alzheimer’s disease, a large amount of research is focused on attacking those plaques as a way to reverse the effect on nerves which leads to AD.

The causes of AD are unknown (notice how much we do not know about this disease). However, it is speculated that it is mostly genetically related, with a large number of genes that underlie this relationship. Despite the internet tropes, there is no rigorous evidence that aluminum causes AD – I wish this belief went away fast.

Since we have no clear understanding of the etiology and pathophysiology of AD, few treatments are available today. Some drugs target the amyloid plaques but have not been shown to change the outcomes of AD.

A couple of medications help manage some of the disease’s symptoms, but they are certainly not cures and they are very expensive. Several drugs at the earliest stages of development may hold out hope of treating the underlying disease, but we are years away from knowing if they work or not.

One more thing that needs to be made clear. There are no biological tests for Alzheimer’s disease — usually, you can only find the amyloid plaques and other pathologies in post-mortem autopsies. Unfortunately. in the absence of an autopsy, clinical diagnoses of AD are “possible” or “probable”, based on other findings, such as memory tests and other methods.

Drugs, vaccines, and dementia paper

In a systematic review published on 21 January 2025 in Alzheimer’s & Dementia, Benjamin R Underwood, Department of Psychiatry and Cambridgeshire and Peterborough NHS Foundation Trust, Windsor Unit, Fulbourn Hospital Cambridge, University of Cambridge, Cambridge, UK, and colleagues reviewed 14 studies using administrative or medical records data for more than 130 million individuals and 1 million dementia cases.

Here are the key results from this study:

• Antibiotics, antivirals, antihypertensives, and anti-inflammatory drugs were all associated with reduced dementia risk.
• The researchers also found a link between the hepatitis A, typhoid, and diphtheria vaccines and lower dementia risk.
• Diabetes drugs, vitamins and supplements, and antipsychotics were associated with an increased risk of dementia.
• This study could not identify individual drugs that reduced the risk of dementia, but they could show classes of drugs that did lower the risk

Why do these drugs reduce the risk of dementia?

The researchers suggested that the protective effects of these prescription drugs may be related to reducing inflammation, controlling infections, and improving overall brain health.

Some research suggests that viral or bacterial infections could cause the development of some common types of dementia. There is evidence that infections that last a few days to several weeks, whether bacterial or viral, can cause damage to the brain. This may result from an enhanced immune response from the body, which can damage brain cells by disrupting brain connections and accelerating memory decline.

Antivirals and antibiotics treat infections, while vaccines prevent infections in the first place, all of which may dampen this excessive immune response. All three types of drugs can significantly reduce the risk of prolonged infections and their devastating consequences for brain health.

This new study provides more evidence that preventing and treating infections may be one of the best and least expensive tools for reducing the risk of developing dementia.

This study also continues to show that vaccines are one of the best medications for preventing dementia and Alzheimer’s disease. Vaccines are inexpensive, safe, and effective, and keeping up with recommended vaccines for adults, including the annual flu vaccine, may prevent dementia in later life.

Citations

• Bohmwald K, Andrade CA, Gálvez NMS, Mora VP, Muñoz JT, Kalergis AM. The Causes and Long-Term Consequences of Viral Encephalitis. Front Cell Neurosci. 2021 Nov 30;15:755875. doi: 10.3389/fncel.2021.755875. PMID: 34916908; PMCID: PMC8668867.
• Lecca D, Jung YJ, Scerba MT, Hwang I, Kim YK, Kim S, Modrow S, Tweedie D, Hsueh SC, Liu D, Luo W, Glotfelty E, Li Y, Wang JY, Luo Y, Hoffer BJ, Kim DS, McDevitt RA, Greig NH. Role of chronic neuroinflammation in neuroplasticity and cognitive function: A hypothesis. Alzheimers Dement. 2022 Nov;18(11):2327-2340. doi: 10.1002/alz.12610. Epub 2022 Mar 2. PMID: 35234334; PMCID: PMC9437140.
• Underwood BR, Lourida I, Gong J, Tamburin S, Tang EYH, Sidhom E, Tai XY, Betts MJ, Ranson JM, Zachariou M, Olaleye OE, Das S, Oxtoby NP, Chen S, Llewellyn DJ; Deep Dementia Phenotyping (DEMON) Network. Data-driven discovery of associations between prescribed drugs and dementia risk: A systematic review. Alzheimers Dement (N Y). 2025 Jan 21;11(1):e70037. doi: 10.1002/trc2.70037. PMID: 39839078; PMCID: PMC11747987.
• Wu X, Yang H, He S, Xia T, Chen D, Zhou Y, Liu J, Liu M, Sun Z. Adult Vaccination as a Protective Factor for Dementia: A Meta-Analysis and Systematic Review of Population-Based Observational Studies. Front Immunol. 2022 May 3;13:872542. doi: 10.3389/fimmu.2022.872542. PMID: 35592323; PMCID: PMC9110786.