Bacteria and viruses that cause issues like Herpes, respiratory illnesses like the flu, and even gum disease aren’t just uncomfortable in the moment: In the long term, they appear to increase a person’s risk of one day developing Alzheimer’s disease.
Research shows that infections may cause the immune system to go haywire, damaging healthy brain cells. There’s evidence that beta-amyloid proteins, which form plaques in the brains of people with Alzheimer’s, are released as a defence against microbes. But to prove a direct link, scientists need to show that vaccination against these illnesses in turn reduce the risk.
Research published in the last year has strengthened the case, leading scientists to call for new trials to definitively prove the vaccines can stop Alzheimer’s.
Shingles vaccines cut dementia risk by 1/5
The Herpes zoster virus, which causes chickenpox early in life, can return with a vengeance when you’re older, causing Shingles. Because people with Shingles develop painful rashes, nerve pain, and other neurological complications, vaccination is recommended by the U.S. Centers for Disease Control and Prevention and many other health agencies.
When the first vaccines for Shingles rolled out in countries like Australia and Wales, only people below a certain age were eligible to receive the vaccine. This created a “natural experiment” where there were two groups of people around the same age, and only some of them received the vaccine.
When controlling for other factors like education, people who got the vaccine were 20 percent less likely to develop Alzheimer’s, with a stronger protective effect on women.
Could other common vaccines also help the immune system fight off Alzheimer’s?
While the Shingles vaccine has the strongest case so far, other studies have found strong links between many other vaccines and Alzheimer’s risk.
As people age, the risk of complications from the flu goes up. In addition to fever, the flu could cause pneumonia and heart attacks. Staying up to date with the flu vaccine cuts down the risk of developing Alzheimer’s by 40 percent, and people who regularly get the vaccine each year have more protection.
Other vaccines that you don’t need to get annually also provide a boost. The Tdap shot that protects against tetanus, pertussis or whooping cough, and diphtheria also reduces the risk of Alzheimer’s by 30 percent. The pneumococcal vaccine, which protects against pneumonia and sepsis, reduces the risk of Alzheimer’s by 27 percent. Meanwhile, the tuberculosis vaccine lowers the risk of Alzheimer’s by 20 percent.
There are many reasons these vaccines might lower the risk. If these viruses spark or accelerate Alzheimer’s, preventing the infection from taking hold stops the process in its tracks. Other scientists think the effects are indirect: Vaccines might teach the immune system to become better at its job, improving its ability to protect the aging brain.
Other scientists think that people who get the vaccine generally live healthier lives than people who don’t get the vaccines. Due to healthier habits like a brain-healthy diet and regular exercise, they are protected against Alzheimer’s.
What’s next for these common vaccines?
Researchers who authored the Wales Shingles vaccine study are calling on funders to support a large Alzheimer’s prevention study. Since the vaccine linked to a lowered risk of the disease is no longer in production, it might be expensive to run the trial. Meanwhile, several groups of scientists are already testing the BCG tuberculosis vaccine in older adults. Since it can take more than a decade to know whether older adults develop Alzheimer’s disease, it may be a while until we know for sure.
In the meantime, making sure you’re up to date on these vaccines prevents common infectious diseases. Preventing Alzheimer’s might be an extra potential benefit.
