A new study suggests the shingles vaccine could reduce dementia risk and may even slow progression in those already diagnosed, offering hope for millions
A recent study finds that older adults who receive the shingles vaccine have a lower risk of developing dementia and may experience slower progression if already diagnosed. This research could provide a simple, widely available way to help protect brain health and improve outcomes for millions of people worldwide.
The original findings are published in Nature, and a follow-up study is available in Cell.
Shingles and dementia: The undiscovered link
Shingles is a viral infection that causes a painful rash and is caused by the same virus that causes chicken pox. Chickenpox is usually contracted in childhood, and the virus remains dormant in the nervous system for life. In older people or those with weakened immune systems, the dormant virus can reactivate, causing shingles.
A study conducted by Stanford Medicine analysed the health records of Welsh older adults and found that those who received the shingles vaccine were 20% less likely to develop dementia over the next 7 years than those who did not.
The findings support the emerging theory that viruses that affect the nervous system can increase the risk of dementia.
Dementia affects over 55 million people worldwide, with an estimated 10 million new cases every year. Dementia research has primarily focused on plaques and tangles in the brain, but with few breakthroughs in prevention or treatment, researchers have begun looking into other areas.
Earlier findings point to a potential protective effect of the shingles vaccine against dementia
Previous studies based on health records have linked the shingles vaccine to lower rates of dementia. Still, these studies did not account for a significant bias: vaccinated people tend to be more health-conscious in ways that are difficult to measure. This includes diet and exercise, which are known to influence dementia rates, but are not included in health records.
“All these associational studies suffer from the basic problem that people who get vaccinated have different health behaviours than those who don’t,” said Pascal Geldsetzer, MD, PhD, assistant professor of medicine and senior author of the new study. “In general, they’re seen as not being solid enough evidence to make any recommendations on.”
Analysing over 280,000 health records
The vaccination program, starting Sept. 1, 2013, created a natural experiment, helping researchers gain trustworthy insights into the vaccine’s effects.
The researchers looked at the health records of over 280,000 adults aged 71-88 years who did not have dementia at the start of the vaccination programme. They focused their analysis on individuals who turned 80 in the week before or after.
“We know that if you take a thousand people at random born in one week and a thousand people at random, born a week later, there shouldn’t be anything different about them on average,” Geldsetzer said. “They are similar to each other apart from this tiny difference in age.”
The same proportion of both groups likely would have wanted to get the vaccine, but only half, those not yet 80, were allowed to by the eligibility rules.
“What makes the study so powerful is that it’s essentially like a randomized trial with a control group — those a little bit too old to be eligible for the vaccine — and an intervention group — those just young enough to be eligible,” Geldsetzer said.
Over the next 7 years, the researchers compared the health outcomes of people of similar age who were eligible for the vaccine with those who were ineligible. By factoring in actual vaccination rates, about half of eligible people received the vaccine, compared with almost none of the ineligible. They could derive the effects of receiving the vaccine.
The shingles vaccine reduced the rate of shingles by about 37% among people who received it during this period. By 2020, one in eight older adults, aged between 86 and 87, had been diagnosed with dementia. Still, those who received the shingles vaccine were 20% less likely to develop shingles than those who were unvaccinated.
The researchers searched for variables that might influence dementia risk but found the two groups indistinguishable across all characteristics. The researchers analysed the data in various ways and still found a strong link between the shingles vaccine and the risk of dementia.
Therapeutic effects on dementia patients
Surprisingly, those who received the vaccine after a dementia diagnosis were less likely to die from the disease, indicating potential to slow its progression and offer new hope.
Overall, nearly half of the 7,049 Welsh seniors who had dementia at the start of the vaccination program died from dementia during follow-up. Still, only about 30% of those who received the vaccine died from dementia.
“The most exciting part is that this really suggests the shingles vaccine doesn’t have only preventive, delaying benefits for dementia, but also therapeutic potential for those who already have dementia,” Geldsetzer said.
