New research has found that people aged 65 and over who’ve received routine vaccinations are significantly less likely to develop Alzheimer’s disease. The study highlights the importance of vaccination not only in protecting against infectious diseases but in providing a degree of protection against dementia.
For most, vaccinations are a part of childhood, designed to protect kids – and the community they’re a part of – from serious infectious diseases. For those at the other end of the life spectrum, other vaccines are considered to be important for the same reasons.
Vaccines given routinely during childhood include those that immunize against tetanus, diphtheria, pertussis (whooping cough) and pneumococcal infection. Tetanus and diphtheria vaccines are bundled up in one vaccine that may or may not include the vaccine for pertussis (Td/Tdap). The pneumococcal vaccine (PCV) is recommended for children under five and adults 65 years and older. Those over 50 in the US and over 70 in Australia and the UK are recommended to get the shingles or herpes zoster (HZ) vaccine.
On the background of accumulating evidence that adult vaccinations may reduce the risk of developing Alzheimer’s disease (AD) and related dementias, researchers from the University of Texas Health at Houston undertook a study to compare the risk of developing AD in adults with and without prior vaccination.
The same researchers had recently discovered that people who’d received at least one influenza vaccine were 40% less likely to develop AD compared to their unvaccinated peers.
“We were wondering whether the influenza finding was specific to the flu vaccine,” said Paul Schulz, corresponding author of the current study. “This data revealed that several additional adult vaccines were also associated with a reduction in the risk of Alzheimer’s.”
The large-scale retrospective study included patients who were free of dementia during a two-year period and were at least 65 by the start of the eight-year follow-up period. The researchers compared two similar groups of patients, one vaccinated with Td/Tdap, PCV, and HZ vaccines, and the other unvaccinated.
Controlling for some sociodemographic and comorbid conditions, they found that there were significant decreases in AD for patients 65 and older who’d received a Tdap/Td vaccination (30% lower risk), an HZ vaccination (25%) or a pneumococcal vaccination (27%) versus unvaccinated groups.
The researchers say that the findings highlight the importance of vaccination not only in protecting against infectious diseases but also in the neuroprotective benefits demonstrated by this study. Although the study does not suggest a causative relationship between vaccines and AD, the researchers have a hypothesis as to why vaccinations might help protect against the disease.
“We hypothesize that the reduced risk of Alzheimer’s disease associated with vaccines is likely due to a combination of mechanisms,” said Avram Bukhbinder, one of the study’s co-authors. “Vaccines may change how the immune system responds to the build-up of toxic proteins that contribute to Alzheimer’s disease, such as by enhancing the efficiency of the immune cells at clearing the toxic proteins or by ‘honing’ the immune response to these proteins so that ‘collateral damage’ to nearby healthy brain cells is decreased. Of course, these vaccines protect against infections like shingles, which can contribute to neuroinflammation.”
Further, prospective studies are needed to specifically measure the impact of vaccines on AD. However, there would be ethical concerns about undertaking a randomized controlled trial where participants are assigned to a group where vaccines, an important method of preventing infection, are withheld.
The study was published in the Journal of Alzheimer’s Disease.
Source: UT Health at Houston
