I turned 48 this week, which meant it was time for my annual physical. After the usual battery of questions from my doctor — How much did I drink? Was I exercising? How was I sleeping? — it was my turn to ask a question. I had one prepared: Should I get the shingles vaccine?

According to standard medical guidance, the answer would be no. The shingles vaccine is only recommended by the government for people 50 years or older; the only exceptions are adults whose immune systems are weakened by disease or treatment. And despite the way my back feels when I get out of bed each morning, I wasn’t there quite yet. Our immune systems weaken as we age, but at 48, I was probably still capable of beating back the varicella-zoster virus that causes shingles (and chickenpox).

And yet my doctor was open to the idea for the same reason that I was asking about it: because there is early but growing evidence that the shingles vaccine may be protective against neurodegenerative diseases like dementia. For someone my age, with more time behind me than in front of me, the possibility of developing those diseases — and the desire to do anything to prevent them — is suddenly looming large.

I’m far from alone. Dementia already afflicts more than 6 million Americans today, and a 2025 study in Nature Medicine estimated that the lifetime risk of developing dementia after age 55 is 42 percent, with higher figures for women, Black adults, and those who carry the APOE ε4 allele genetic variant, which is known to increase the risk for Alzheimer’s. That same study projected new US cases of dementia would double by 2060, from 514,000 a year in 2020 to more than 1 million annually, due largely to population aging.

Behind those figures is a universe of suffering. Nearly everyone reading this has watched, or will watch, someone they love succumb to dementia. And once you get to my side of your 40s, that risk starts to feel less abstract and a lot more personal.

Yet the frightening story of the rise in dementia cases as the US population ages obscures real progress that is already being made to prevent it — and the even greater progress that could follow. Dementia may feel inevitable, a cruel side effect of longer life. But it doesn’t have to be.

The Nature study is about incidence — new cases, not the total number of people living with dementia. Separate CDC estimates project nearly 14 million older Americans living with Alzheimer’s disease, the most common form of dementia, by 2060.

But the rate hasn’t been holding steady — it’s been dropping. A 2020 study that drew on data from six countries across Europe and North America found that age-specific dementia incidence for people of European ancestry had fallen about 13 percent per decade since the late 1980s, and around 16 percent per decade for clinical Alzheimer’s. A 2016 study tracked five-year dementia rates across four periods between the late 1970s and the early 2000s and found them steadily falling, ultimately dropping 44 percent by the most recent period. The authors of the 2020 study project that if the decline in incidence remains steady in the future, 15 million fewer people might develop dementia by 2040 across high-income countries than if the incidence of the disease remained unchanged.

That good news may not be shared by everyone. The 2016 study found that the decline only showed up among people with at least a high school diploma — more on that below — and even then, it wasn’t evenly shared. And the sheer increase in older people means that a continually dropping incidence only blunts the coming dementia wave, rather than blocking it. One study of older adults in England actually found dementia incidence falling through 2008 and then creeping back up; the researchers also found that when you account for the fact that people headed toward dementia tend to die earlier, the drop gets much harder to see. What’s fallen before can rise again.

But what this likely means in practice is that a person turning 80 today is meaningfully less likely to have dementia than a person who turned 80 a generation ago. And it’s reasonable to hope the same will hold for whoever turns 80 next — like, say, me.

The question, though, is why.

Here’s a veteran health journalist tip: if anyone ever asks you why something is improving in public health, just attribute it to the decline in smoking. There’s a decent chance you’ll be right.

While Alzheimer’s is a brain disease, and dementia is the umbrella term for several kinds of cognitive decline, there is a growing consensus that they are deeply driven by vascular health — meaning what damages your heart and blood vessels is ultimately what damages your mind. Thanks to the development of blood pressure and cholesterol-lowering medicines, better heart disease and stroke management, and perhaps most of all, drastic reductions in smoking, cardiovascular health has been improving. Even with the rise of obesity and diabetes, most vascular risk factors have decreased over the same time that dementia and Alzheimer’s prevalence fell.

The rise in education over the same time period may play a role as well. Americans turning 80 today went to school during a great mid-century expansion in education, while their parents were schooled — or rather, not schooled — in the 1920s and ’30s. In 1940, only 24.5 percent of Americans 25 and older had a high school diploma, and just 4.6 percent had completed a bachelor’s degree or more. By 2017, high school completion had reached 90 percent, and the share of people with a bachelor’s or more had hit 34 percent. And researchers have correlated higher education attainment with lower dementia and Alzheimer’s rates.

Now repeat after me: correlation is not causation. Researchers don’t really know why more years of schooling seem to be associated with a lower risk of dementia, though there are theories that education might boost the brain’s “cognitive reserve.” But the hopeful take is that the decline in incidence is largely driven by behaviors and life conditions we can change. And one of the most unexpected and promising acts is something as simple as routine vaccination.

Last April, I wrote about what I called “one of the brightest spots in an otherwise dark field”: a study in Wales that found that older adults who received a vaccine against shingles were 20 percent less likely to develop dementia in the seven years following vaccination than those who did not receive it. It wasn’t a randomized trial, but it was stronger than the usual observational association: the study harnessed a natural experiment in Wales, where vaccine eligibility turned on a birthday cutoff, meaning it was less likely that the results were because vaccinated people were simply healthier.

Earlier this year, a study in Canada looked at hundreds of thousands of people over the age of 70 and, like the Welsh study, found that those who had taken the shingles vaccine were less likely to develop dementia. And a new analysis from late 2025 of the data in the Welsh study found that the vaccine was associated with benefits that went beyond prevention — it also seemed to slow the disease for those with dementia and reduced deaths attributable to it.

The shingles vaccine in the Welsh study was an older, live-virus version; the current vaccine is a newer recombinant form that can’t accidentally cause shingles, and another study found it was associated with even greater protection from dementia.

These findings are promising but still leave plenty of questions. The Welsh live-vaccine study found a larger apparent benefit in women, who also suffer higher rates of dementia. But the pattern is not settled: the newer recombinant-vaccine study found an association in both men and women, though stronger in women. Shingles may be connected to dementia, though the evidence is still messy: A large 2025 health-records study found recurrent shingles was associated with a modestly higher dementia risk than a single episode, while earlier evidence has been more mixed.

Shingles occurs when the dormant varicella zoster virus — the same virus that causes chickenpox — reactivates. It’s possible that the resulting neural inflammation may feed dementia. A randomized controlled trial published in December tested a related herpes-virus idea, treating 120 adults with early Alzheimer’s or mild cognitive impairment — all with evidence of prior herpes simplex infection — with a medication called valacyclovir. After 18 months, researchers found no significant advantage over a placebo, dampening hopes that herpes antivirals could be an effective Alzheimer’s treatment.

That’s a real strike against the simplest version of the theory that the virus itself is rotting the brain. But it could mean that the shingles vaccine’s possible protective effects don’t come from shingles at all. A 2025 study found that the newer shingles vaccine and an RSV vaccine that share the same AS01 immune-boosting adjuvant were each associated with lower 18-month dementia risk compared with flu vaccination, and researchers did not find a statistically significant difference between the two AS01 vaccines. The implication is that the benefit might come from giving an aging immune system a jolt, rather than from any one bug it’s aimed at.

But as the vaccine science sorts itself out, there are lifestyle changes you can make to help protect yourself without getting a shot. A 2024 Lancet commission found that, in principle, up to 45 percent of dementia cases could be prevented or delayed by addressing 14 risk factors, including not smoking; lowering high LDL cholesterol in midlife; treating hearing loss, especially from midlife on; and limiting obesity. The key period here is midlife, which the commission defined (rather widely in my opinion) as 18-65. Which, for someone my age, means there’s no better time to focus on prevention.

I don’t know whether I’ll go ahead and try to get the shingles vaccine early, and to be clear, I’m not telling anyone they should. The science is still uncertain, and I am, obviously, not a medical doctor. But the lifestyle factors that have been shown to protect against dementia — which are largely the same ones that help cardiovascular health — can be adopted by everyone, for their health now and in the future.

No one knows for sure what the future holds, for me or for you. What’s certain is that, barring a medical miracle, the sheer number of dementia cases will continue to rise as our population ages, and that some of us will be in that number. But that doesn’t mean we’re helpless.

A version of this story originally appeared in the Good News newsletter. Sign up here!