• Recent research from UTHealth Houston suggests that the administration of some vaccinations, including those for tetanus, diphtheria, pertussis (whooping cough), shingles (herpes zoster), and pneumococcus, are associated with a reduced risk of developing Alzheimer’s disease.
• Previous research revealed that individuals who had received at least one influenza vaccine had a 40% lower probability of developing Alzheimer’s disease compared to those who had not received any vaccination, leading researchers to investigate other vaccines.
• These new findings are particularly notable as they point to a practical and accessible way for Alzheimer’s prevention, emphasizing the advantages of routine adult vaccinations.

In a new study whose results appeared in the Journal of Alzheimer’s Disease, researchers found that several vaccines commonly given to adults were similarly linked to a decreased likelihood of developing Alzheimer’s disease.

Scientists from the Neurocognitive Disorders Center at McGovern Medical School in Houston, TX, explained that both their team and other experts in the field hypothesize that the immune system could be responsible for instigating dysfunction in brain cells in Alzheimer’s disease.

The findings from this new study suggest that vaccination might have a broader impact on the immune system, leading to a reduced risk of developing the disease.

Whooping cough vaccine tied to 30% lower Alzheimer’s risk

To explore this hypothesis, the researchers conducted a retrospective cohort study involving patients who were dementia-free for a period of 2 years prior and were at least 65 years old at the commencement of an 8-year follow-up period.

They carried out a comparison between two groups of patients, one group vaccinated against tetanus, diphtheria, and pertussis (Tdap/Td), herpes zoster or shingles (HZ), or with pneumococcal vaccines, and another group that remained unvaccinated, using propensity score matching to ensure the groups were similar.

When the researchers looked at different people, they found that those who got the Tdap/Td vaccine were 30% less likely to get Alzheimer’s compared to those who did not get the vaccine.

Kristofer Harris, co-first author on the study and program manager in the Department of Neurology with McGovern Medical School at UTHealth Houston, spoke to Medical News Today, saying the team “found that there is a decreased risk of Alzheimer’s disease for older adults who received routine vaccinations.”

“The risk of Alzheimer’s disease was reduced by 30% with Tdap/Td vaccination, 25% with shingles vaccination, and 27% with pneumococcal vaccination when we compared to those who did not receive those respective vaccinations,” he noted.

“This study goes hand in hand with our previous research, which found that people who received at least one flu vaccine were 40% less likely to develop Alzheimer’s disease when compared with those who were not vaccinated.”

– Kristofer Harris

How might vaccines lower Alzheimer’s risk?

It could be that vaccines change how the immune system acts when there are harmful proteins building up in the brain, a process linked to the development of Alzheimer’s disease.

They might also help immune cells work better in cleaning up these harmful proteins or they could improve the immune response, helping to protect healthy brain cells nearby.

The findings from the study contribute positively to both Alzheimer’s disease prevention research and public health overall, underscoring the importance of vaccination.

Dr. David Merrill, geriatric psychiatrist and director of the Pacific Neuroscience Institute’s Pacific Brain Health Center in Santa Monica, CA, not involved in the study, said that “these findings are consistent with prior work showing that getting the flu shot also lowers risk of developing [Alzheimer’s disease].”

“Now that three additional vaccines have been shown to have this effect, it suggests that perhaps vaccines are working through some additional shared immune-system mediated mechanism to reduce risk of [Alzheimer’s disease],” he added.

However, “older adults who get vaccinations may also be more likely to take care of themselves in general,” Dr. Merrill suggested.

“Vaccination status may be a proxy for the general degree to which an individual is taking care of themselves with aging. We now know that a whole host of health factors can change the risk of developing [Alzheimer’s disease]. These include control of blood pressure, dietary habits, exercise routines, sleep, and stress levels.”

– Dr. David Merrill

Experts comment on vaccines and Alzheimer’s risk

Dr. Marshall L. Nash, medical director for the NeuroStudies subnetwork at the Accel Research Sites Network, told MNT that “the hallmarks of Alzheimer’s disease diagnoses center around detecting abnormal accumulation of amyloid and tau proteins as well as neuroinflammatory markers.”

“This study confirms that decreased exposure to common infections known to cause neuroinflammation reduces the risk of developing subsequent cognitive impairment,” he added.

“We currently have several trials designed to specifically limit neuroinflammation and therefore aim to slow or reverse [the] progression of decline leading to Alzheimer’s disease,” noted Dr. Nash. “This area of study will continue to grow as we confirm a similar reduction in cognitive decline with COVID vaccine treatments.

Potential implications for patients and the public

Harris noted that their research “emphasizes the important role that vaccines may play in reducing the risk of Alzheimer’s disease.”

“We believe that vaccines exhibit a protective effect due to a number of factors, which include prevention of the infection from occurring, diminishing the severity of the infection, helping the immune system to remove Alzheimer’s disease pathology — such as amyloid plaques — and decreasing the amount of inflammation occurring in brain cells.”

Kristofer Harris

“This study illustrates the positive value of vaccinations, and the potential impact that vaccines can have on other diseases such as Alzheimer’s disease,” Harris explained.

Dr. Merrill agreed, saying that “it’s important to get vaccinations and stay up to date on your vaccinations.”

“They offer protection against the diseases they are being given for and may even lower the risk of developing [Alzheimer’s disease] down the line.”

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