There are countless things we believe we know about dementia—and that familiarity comes from the disease’s unfortunate prevalence. In the U.S. alone, the Centers for Disease Control and Prevention (CDC) estimates that nearly 5.8 million people are living with dementia. Hearing about “dementia” or “Alzheimer’s disease” sparks fears of lost memories, changes in mood and behavior, and increased risk as you age. But one common belief about dementia was recently dispelled by an important new study. Read on to find out what researchers have just learned about dementia risk factors.
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Dementia and Alzheimer’s disease, the most common form of the condition, are a hot topic for research, as no cure or effective treatment currently exists. Studies have identified a variety of risk factors for the disease, including snoring, hypertension, and even failing to brush your teeth.
With so much information available about dementia, it can be overwhelming to know how to best mitigate your chances of developing cognitive decline. But new findings suggest that you can cross one concern off your list—even if it’s something you already had.
If you’ve had shingles, you may not need to worry about heightened dementia risk—despite what previous studies have said. Shingles, a common disease also known as herpes zoster, and chickenpox are both caused by the varicella-zoster virus. According to the CDC, when first infected with the virus, you develop that itchy chickenpox rash, but the virus can stay dormant in your system even after you’re better. This makes you susceptible to shingles—which causes a painful rash on one side of the body—when the virus reactivates later in life.
Studies have suggested that shingles infection increases your risk of dementia, while others have found no association, Medical News Today (MNT) reported. The spiked risk was thought to be caused by shingles’ potential to cause inflammation in the brain, infect brain cells, or damage blood vessels in the brain.
But a study published in Neurology on June 8 found that shingles infection—while a concerning condition on its own—was not associated with an increased risk of dementia.
“The study adds growing evidence from other countries including the United Kingdom that shingles, despite leading to other complications including post-herpetic neuralgia, does not generally raise dementia risk,” Charlotte Warren-Gash, PhD, associate professor of epidemiology at the London School of Hygiene and Tropical Medicine, told MNT.
The study utilized data from the national Danish registries, including information from 247,305 participants over the age of 40 years with herpes zoster, and 1,235,890 comparators from the general population. When evaluating data from participants, researchers found a small decrease in dementia risk for those who previously had the herpes zoster virus, when compared with the general population. But researchers also issued a word of caution about this finding.
“This was unexpected and we cannot explain the reason for the findings in our study,” Sigrún Alba Jóhannesdóttir Schmidt, MD, study author and epidemiologist at Aarhus University Hospital in Denmark, told MNT. “It is possible that it is simply due to missed diagnoses of zoster in people with undiagnosed dementia, because people with cognitive problems may not react to symptoms or seek healthcare for zoster. This would make it look like zoster leads to a lower risk of dementia even though this is not the case.”
Schmidt also noted that this could be due to antiviral drugs that treat zoster, suggesting that these drugs protect against dementia. But investigators were unable to look further into this hypothesis, she said.
Within the study, there was a small group of participants who did develop encephalitis (inflammation of the brain) after shingles affected their central nervous system, Warren-Gash told MNT. This group did see a higher risk of dementia.
“However, encephalitis from other causes is also linked to raised dementia risk, so the association is not specific to shingles,” Warren-Gash said.
She further commented on the available vaccines for the varicella-zoster virus, adding that they may help lower risks associated with shingles, but probably don’t play a role in dementia. “While shingles vaccines effectively reduce the risks of shingles and its known complications, they are unlikely to be effective for dementia prevention,” she explained.