Alzheimer's disease (AD) affects almost 7 million Americans. Researchers believe that number will more than double by 2060, with African American and Hispanic patients being more frequently diagnosed.
Researchers believe a number of factors play into the development of AD, with research pointing to a connection between Herpes simplex virus 1 and AD.
Experts think this connection could lead to treatment and prevention strategies against AD.
Alzheimer's disease (AD) is a serious health concern, causing irreversible, progressive neurodegenerative damage to patients. About 6.7 million Americans over the age of 65 live with AD. However, about 200,000 younger Americans—those under 65—also have a younger-onset type. Now, researchers suggest a link between AD and Herpes. 
AD is a leading cause of death in the US, resulting in nearly 122,000 deaths in 2019. AD is expensive, too—costing patients $345 billion in care services. At present, researchers say there are no truly effective treatments nor preventative therapies.
AD is part of the dementia umbrella. Dementia is a term that represents a number of symptoms associated with cognitive decline, including memory loss, loss of reasoning skills, and loss of thinking skills. AD is responsible for 60-80% of dementia cases.
AD incidence also seems to be increasing—and impacting different ethnic groups disproportionately. According to the Centers for Disease Control and Prevention (CDC), the number of AD cases are expected to more than double by 2060, when, they say, it will affect an estimated 14 million people. By then, Hispanic and Black patients will make up the majority of cases.
While the underlying etiology of AD isn’t totally understood, researchers believe amyloid plaques—described as “tangled bundles of fibers” referred to as either neurofibrillary or tau tangles—play a key role in addition to neuron connections issues and neuroinflammation.
Of course, AD is a complex disease owing to a myriad of other influences. Researchers believe that genetics, being female, having a lower level of education, and environmental factors also play a role. Lifestyle behaviors (like smoking, diet, how much exercise one gets, and alcohol consumption) can also influence AD development.
How herpes comes into play
More so, researchers believe that other diseases (like sleep disorders, diabetes, cardiovascular disease, and obesity) play a role as well. On that topic, recent research published in the Journal of Drugs in Dermatology found an association between infection with Herpes simplex virus 1 (HSV-1) and AD. The research team conducted a search of PubMed, Embase, and Web of Science for articles on HSV-1 with AD. They drew from 21 pieces of information, including two review articles and 19 population-based and case control, cohort, and cross-sectional studies.
As the researchers explained, herpesviridae is a class of viruses that are common causes of mucocutaneous pathologies. The researchers say that the “neurotropic nature of HSV-1, as well as its ability to establish dormancy in the sensory root ganglia of the trigeminal nerve,” has led to its being a target of research as a potential infectious etiology for AD.
“Various pathophysiologic mechanisms centering around neuroinflammation evoked by the virus in genetically susceptible individuals have been proposed,” they write. “Recent studies demonstrate a strong correlation between HSV-1 and AD; however, treatment of HSV-1 for prevention of AD is not currently the standard of care. Due to the high prevalence of HSV-1 in the adult population, focusing on HSV-1 antiviral suppression may be a reasonable course of action considering the possible link to AD in this cohort.”
Raj Dasgupta, MD, explains how this connection could be made: “HSV-1 infection triggers an inflammatory response in the brain that might damage neurons and eventually lead to AD,” he says. “If the link between HSV-1 and AD is confirmed with additional studies, it could have major implications for the prevention and treatment of AD.”
Dasgupta says this discovery could potentially lead to the development of antiviral medications or even vaccines that could prevent or delay AD. More so, it could result in the development of new treatments for AD that specifically target HSV-1 infection, Dr. Dasgupta says.
This connection between AD and HSV-1 largely influenced how Heather Sandison, ND—who specializes in neurocognitive medicine—practices. She says that a 2018 study published in Neurotherapeutics explored the connection between HSV-1 and dementia, finding that “antiherpetic medications in the treatment of HSV infections was associated with a decreased risk of dementia.”
“This new study [in Journal of Drugs in Dermatology] further validates existing research linking herpes viruses to Alzheimer's and dementia risk,” Sandison says. “As a clinician, I treat herpes outbreaks aggressively in my patients because of this link to cognitive decline.”
Sandison says clinicians should openly talk to their patients about safely and effectively treating and preventing HSV-1 infections. “This may help be part of a holistic strategy for preventing cognitive decline,” she says.
But beyond the HSV-1 element, Sandison stresses that patients should also be made aware of the toll other factors can take, including “sleep deprivation, social isolation, uncontrolled diabetes and heart disease, obesity, depression, hearing loss, and a sedentary lifestyle”—all of which she says are modifiable risk factors for dementia. “There is a lot we can do to prevent cognitive decline as we age,” she says.