According to a new study from UTHealth Houston, people who had at least one flu vaccine were 40% less likely than those who were non-vaccinated to develop Alzheimer’s for several years. To get a deeper understanding of these results and the link between the flu shot and Alzheimer’s, we spoke to several doctors.
The Connection Between the Flu Shot and Alzheimer’s
While we all want to see progress in understanding causes, treatments and prevention strategies against Alzheimer’s disease, this type of study has to be looked at with caution. The idea that the flu vaccine (or any other vaccine) protects against Alzheimer’s disease brings out a healthy skepticism, Allison Reiss, MD, Inflammation Laboratory Head at the Biomedical Research Institute at NYU Langone Hospital—Long Island and Associate Professor of Medicine at NYU Long Island School of Medicine, explains. In this study, the authors accessed a huge database of older insured people and looked back (retrospectively) to see whether they had received a flu vaccine and then whether they developed dementia. Researchers used diagnosis codes for the analysis and gathered reams of data, but not any in-depth or personal records or neurologic evaluation. They assumed dementia to be Alzheimer’s, so a fair number of cases would have been dementia from causes other than Alzheimer’s. They also did not attempt to figure out how many flu shots a person received over the study period (yearly versus only one). They tried to account for as many confounding factors (things that could distort the results) as possible, but ultimately, there is a lot of room for error and spurious associations, Dr. Reiss adds. This study indicates that there could be a link between the flu vaccine and lower Alzheimer’s risk, but they cannot say that this is cause and effect nor can they explain the reason for the link. They rightly explain that further (preferably prospective) studies are needed.
Understanding the Immune System and Alzheimer’s Disease
Study authors also note that the immune system is complex, and certain health conditions, like pneumonia, may affect it in a way that worsens Alzheimer’s. However, other factors that affect the immune system may, in fact, help protect people against this neurocognitive disorder. “We know from seeing Alzheimer’s patients every day that many things that activate the immune system make them worse. Urinary tract infections, pneumonia, and a broken bone are common examples,” says Dr. Paul E. Schulz, a neurologist with UTHealth Houston. “After an AD patient recovers from them, they may get back to their baseline thinking state, or they may not.” As a result of these observations with AD patients, Dr. Schulz says he is leery about his patients undergoing surgery and tells them it’s better to get a flu vaccine than not since the flu can be deadly as we get older. However, Dr. Schulz explained that initially, he thought that the inflammation caused by vaccination could, in theory, also make them worse. Just like pneumonia. “I was very surprised to find that the influenza vaccination helps reduce the risk for AD instead of enhancing it,” he says. “From this result, we surmise that some factors can turn on the immune system in a way that is potentially deleterious to our AD patients, as we have seen with infections.” On the other hand, other manipulations that activate the immune system, specifically influenza vaccination, appear to have the opposite effect, such as reducing the risk for AD. The ways in which the immune system are activated are very important, obviously, but we really don’t know how those two situations differ, resulting in very different outcomes, Dr. Schulz explains. It will be important now to try to understand those differences. If we understood why infections result in poorer outcomes, we could stand a chance of intervening to prevent that. And, if we discover how vaccinations help reduce the risk for AD, perhaps we could stimulate that pathway directly to further reduce the risk of AD, Dr. Schulz adds. “Neuroinflammation (inflammation in the brain) that occurs acutely in response to toxins or damage, may be part of a repair process that is neuroprotective in Alzheimer’s disease and other types of brain injury,” says Dr. Reiss. “The microglia, or immune cells of the brain, may participate in clearing away damaged neurons.” However, neuroinflammation (although not the cause of Alzheimer’s) is a part of the destructive process in Alzheimer’s disease when it is chronic and ongoing for a prolonged period. It is similar to forming scar tissue which is good for repairing wounds, but if the scar tissue grows to excess and out of control, it can restrict movement or damage organs, Dr. Reiss explains.
What This Study Can Tell Us About the Future of Alzheimers Research
The study shows how we can use our collected medical information to find clues about Alzheimer’s and other disease states. “We must use the information gleaned from big data with care and follow-up with rigorous, controlled prospective studies, as much as possible and ethical, to get more definitive answers and to uncover true cause-and-effect relationships, mechanisms, and possible new prevention/treatment approaches,” Dr. Reiss states. “Understanding the role of the immune system in AD has now become very important in a way that we didn’t anticipate, says Dr. Schulz. “Understanding how the flu vaccine reduces the risk for AD by a large amount has also moved way up on our priority list. We don’t have anything else that reduces the risk for AD by 40%. Capitalizing on this finding is essential.” Dr. Schulz and his research team have started investigating other vaccination effects now to see if others work and to see if combining the influenza vaccination with the shingles ones (like Shingrix) or the pneumonia ones (like Pneumovax) leads to even greater risk reduction for AD.
Factors That Can Contribute to the Development of Alzheimer’s
Learning what can cause Alzheimer’s is a crucial step in finding ways to treat it. “Modifiable factors that may be important in delaying or preventing Alzheimer’s disease include a balanced diet, controlling blood sugar and blood pressure, physical activity, refraining from excess alcohol consumption and avoiding head injuries,” says Dr. Reiss. A healthy brain requires a healthy heart and circulation, so take care of your cardiovascular system. Many people avoid too much sun exposure for health reasons and the Covid pandemic kept people isolated indoors for long periods and this led to a lot of vitamin D deficiency. This is often unnoticed, but easy to remedy with vitamin D-rich foods or supplements. “I generally believe it is best to get vitamins from food rather than pills, but vitamin D is the one possible exception,” Dr. Reiss adds. It’s been difficult to find “the cause” of AD, Dr. Schulz explains. However, we know many factors that increase or decrease the risk of getting it:
Physical exercise is agreed by most investigators to help reduce risk. Aerobic exercise for about 20 minutes, 4 or more times per week, appears to be enough to see changes. Mental exercise is also agreed to be beneficial. Everyone studied has been helpful, so we don’t recommend a particular one- we suggest whatever a person likes, and hence will perform. Examples include discussing politics, doing crossword puzzles, and doing Sudoku. The cardiovascular risk factors that we all know about are also generally agreed to accelerate or slow AD progression, depending on whether we address them or not. This includes diabetes, high cholesterol, high triglycerides (blood fats), and high blood pressure.Long-term depression may be a risk, so treating it is recommended.PTSD also appears to double the risk for AD.
Next up: The Crucial Brain-Boosting Tips Maria Shriver Lives By—And Why She’s Hopeful About Alzheimer’s Research
Sources
Alzheimer’s & Dementia: “2021 Alzheimers disease facts and figures”UTHealth Houston: “UTHealth Houston study: Flu vaccination linked to 40% reduced risk of Alzheimer’s disease”Allison Reiss, MD, Inflammation Laboratory Head at the Biomedical Research Institute at NYU Langone Hospital—Long Island and Associate Professor of Medicine at NYU Long Island School of MedicineDr. Paul E. Schulz, a neurologist with UTHealth Houston
