The Shingles Vaccine: Compelling research shows reduced dementia risK

Almost everyone knows and loves someone who was once connected to the world, living a meaningful life in community with others, and considering the future – and then dementia slipped through the back door. That once-vibrant person is now confused, often with profound memory loss, mood instability, irrationality, anxiety, an inability to reason, and a personality not even vaguely resembling the individual once known and loved. It is a relentless thief, estimated by the World Health Organization to affect more than 57 million people globally and is the 7th leading cause of death worldwide.

Dementia: what is it?

Dementia is a general term defining various neurological conditions that cause a decline in cognitive abilities such as thinking, remembering, reasoning, and problem solving. Dementia impairs daily life and often worsens over time. It is not a specific disease, but rather a syndrome caused by various diseases or injuries that damage the brain. The most common dementia is Alzheimer's disease, considered “progressive” and accounting for 60-70% of cases. Other conditions in this category include vascular dementia, Lewy Body dementia, and frontotemporal dementia. 

Whatever the type of dementia, it is largely believed to be caused by damage to or loss of nerve cells and their connections in the brain. Depending on what part of the brain is affected, the symptoms vary, affecting people differently. Although there is no known cure, early diagnosis and management can improve the quality of life both for the affected individual and those who care for the person.

Can it be avoided?

Until recently, there was very little known about ways to reduce the likelihood of an individual getting dementia; it seemed to fall into the vast category of health conditions determined by luck and maybe some genetic predisposition.  And then came an analysis of an unusual public health policy in Wales with exciting findings: the shingles vaccine appeared to decrease the likelihood of an individual being diagnosed with dementia by 20%, more than any other known intervention.

What happened in Wales?

On September 1, 2013, the Welsh government implemented a shingles vaccine policy with strict age parameters: all individuals who were 79 years old by that day were eligible for the vaccine for exactly one year. Anyone 80 or older (on that day) was deemed ineligible based on both an understanding that the vaccine was less effective after that age and because Wales had a limited supply of the vaccine. As people turned 79, they became eligible to receive the vaccine for a year as well, in a sort of “rolling admissions” policy. In this way, it set up a “natural experiment,” notes Dr. Pascal Geldsetzer, Assistant Professor of Medicine at Stanford Medical School. He explains that this model handed scientists the opportunity to compare groups of people who had similar characteristics.  “If I take 1,000 people born one week and 1,000 people born one week later, there shouldn’t be any difference between them, except for the large difference in the vaccination uptake,” said Dr. Geldsetzer. He and his team then followed the health of approximately 280,000 individuals aged 71-88 for seven years who did not have dementia when the public health policy was implemented. Over this period of time, almost half of the people who were eligible received the vaccine.

In Wales, those who fit the eligibility criteria and received the vaccine were 20% less likely to develop dementia over the next 7 years than their counterparts who did not receive the vaccine. Moreover, women, who are considered typically to have more reactive immune systems and greater antibody responses to vaccines than men, exhibited greater protection from dementia than men, a finding that also held true for those with autoimmune disorders and allergies.

Why would shingles vaccines be protective against dementia?

There are several ideas about what forces might be at play to reduce the likelihood of dementia following a shingles vaccine, with two dominant theories. One theory is that the vaccine prevents the individual from having an episode of shingles and, by avoiding that episode, the individual also avoids experiencing the neuroinflammation that is caused by the shingles. As Dr. Geldsetzer explains, “Inflammation is a bad thing for many chronic diseases, including dementia,” so “reducing these reactivations and the accompanying inflammation may have benefits for dementia.”  The other theory suggests that the vaccines “rev up” the immune system and by doing so, protect people from whatever conditions might make them more vulnerable. Whether these two theories are correct, or something else entirely is at play, Dr. Geldsetzer’s team has now been able to replicate the Welsh research findings in four other countries, affirming the link between the shingles vaccine and reduced dementia risk. (For those at increased risk for dementia because they carry a specific gene, the benefits of avoiding an episode of shingles is theoretically even greater.)

What is “shingles” anyway and is it bad to get it?

Shingles is a viral infection that is caused by the same virus, varicella-zoster, that causes chickenpox. If an individual has had chickenpox (which often happens in childhood), the virus typically becomes dormant in the nerve cells – possibly forever or until something reactivates it. That “something” can be stress, other medical conditions, or a variety of factors that weaken immune systems.

Shingles usually produces a painful rash initially evident by a string of blisters and, while not life-threatening, a condition that is arguably great to avoid. It often lasts for a week or two (although can last longer) and, on rare occasions, includes complications, the most serious of which can lead to a loss of vision. The most common complication is called “postherpetic neuralgia,” a kind of nerve pain that lingers after the infection. Preventing the shingles, or even shortening the duration of a shingles episode and lessening the likelihood of complications, is worthwhile, which is reason to consider a shingles vaccine.

Given the research findings from Wales (and now four additional countries), the fact that a shingles vaccine reduces the risk of dementia significantly is a clear win for now.