Getting your annual flu shot can have an important secondary benefit: helping protect you from dementia.

Numerous studies have found that older adults vaccinated against the flu had a lower risk of developing dementia in later years than those who had not been vaccinated. In one study, the risk was up to 40 percent lower.

Research published earlier this month has reinforced that evidence, showing that older adults who received a higher dose of the flu vaccine — commonly recommended for people 65 and older — were even less likely to develop Alzheimer’s disease compared to those who received the standard dose.

Other common medications have also been found to lower people’s risk of dementia. However, the challenge for scientists is to determine whether the drugs directly benefit the brain or if there is only a correlation between them.

The flu vaccine is a good example of this. “The people who tend to get vaccinated are the ones who go to the doctor, and then follow the instructions to take their blood pressure and cholesterol pills, which also reduce the risk of Alzheimer’s,” said Paul Schulz, a professor and neurologist at UTHealth in Houston who led the new study.

But because all participants in that study were vaccinated against influenza, and the higher dose offered more protection, the results suggest that there is something about the vaccine itself, and not the people’s behavior, that reduced the risk, Schulz said.

Here are some of the other drugs that scientists are investigating for their potential to reduce the risk of dementia.

Shingles vaccine

There is particular enthusiasm for the shingles vaccine, which has some of the strongest research. Studies from around the world have found that people who received the vaccine had a lower risk of developing dementia, often by 15 to 20 percent. Much of the research has been done on an older form of the vaccine, but at least one study indicated that a newer version more commonly prescribed in the United States, called Shingrix, could offer even greater benefit. It appears that (along with the flu vaccine) it particularly protects women against dementia.

Researchers say they are relatively confident that the vaccine itself provides protection because its initial rollout in a few countries created a kind of natural clinical trial.

“I think at this point, this is a really compelling body of evidence for a cause-and-effect relationship,” said Pascal Geldsetzer, an epidemiologist at Stanford’s Knight Initiative for Brain Resilience, who led some of the research.

There are a couple of theories about how vaccines might reduce the risk of dementia. One is that, by protecting people from getting an infection, a vaccine prevents the immune response and especially the inflammation that comes with it. (Inflammation is known to contribute to dementia.) This may be especially relevant for shingles, as the virus initially replicates in the nervous system and can cause inflammation in the brain.

It is also possible that the vaccines themselves alter the immune system in a way that directly affects and protects the brain.

Medications for cholesterol and blood pressure

Several studies have found that both statins and drugs that treat hypertension are associated with a 10 to 15 percent reduction in the risk of dementia.

Many researchers think that these drugs protect people’s brains by helping to control blood pressure and cholesterol, which are risk factors for dementia. However, as with vaccines, someone who consistently takes prescribed medications can engage in other healthy behaviors that could also reduce their risk.

Most research is observational in nature, but there have been some clinical trials that have attempted to more directly study the connection between these drugs and dementia. The results have been uneven. A trial in China in 2025 found that people with high blood pressure who were given a hypertension drug had lower rates of dementia four years later. But a 2009 trial that tested statins in people who had vascular disease or were at high risk for it found no benefit in preventing cognitive decline.

Also open is the question of whether people who don’t need heart-health medications could take them to prevent dementia, said Geoffrey Joyce, professor of pharmaceutical and health economics at the University of Southern California. There are currently two large trials investigating whether statins might be useful in this way.

Anti-inflammatory medications

Because brain inflammation is known to contribute to Alzheimer’s, it is possible that anti-inflammatory medications could provide protection by helping to reduce inflammation both in the brain and throughout the body. A recent large-scale review article listed anti-inflammatories as one of the classes of drugs that may reduce the risk of dementia.

David Llewellyn, a professor of clinical epidemiology and digital health at the University of Exeter Medical School in England, who led the review, said he thought “the history of anti-inflammatories” made scientific sense.

But studies looking at the connection, especially with nonsteroidal anti-inflammatories, have been contradictory. Some have found a lower risk of dementia from ibuprofen use, while others showed no connection or even showed an increased risk. And a Cochrane review published in 2020 concluded that “there is no evidence to support the use” of aspirin or other nonsteroidal anti-inflammatory drugs to prevent dementia.

Diabetes drugs

Diabetes is associated with an increased risk of dementia, and some type 2 diabetes drugs, such as metformin and a class of drugs called sodium-glucose cotransporter 2 (SGLT2) inhibitors, appear to slightly reduce that risk, although some studies show no effect.

The possible benefit is thought to be largely due to the ability of these drugs to help control insulin and blood sugar levels, which affect the health of brain cells. There is also some evidence, especially in animals, that the drugs help reduce inflammation and may even lower levels of amyloid beta in the brain, a key protein implicated in Alzheimer’s.

Clinical trials are underway investigating whether these diabetes drugs may be beneficial in cases of dementia.

Some observational studies have also found that people with diabetes who took the new GLP-1 drugs had a lower risk of developing Alzheimer’s, even as high as 45 percent, according to some reports.

Building on this evidence and research with mice showing that the drugs can reverse cognitive decline, two clinical trials recently tested whether a pill form of Ozempic could also help slow cognitive decline in people with Alzheimer’s. But the trials revealed no benefit, and enthusiasm for using GLP-1 as a treatment for Alzheimer’s disease has waned considerably. More research is needed to determine whether they really reduce the risk of dementia.