Oral Herpes Tied to Double Dementia Risk in Older Adults

TOPLINE:

A history of herpes simplex virus (HSV) is associated with a more than doubling of the risk of dementia in older people, results of a prospective epidemiological study showed. 

METHODOLOGY:

• The study included 1002 dementia-free 70-year-olds from the Prospective Investigation of Vasculature in Uppsala Seniors cohort who were assessed at baseline and at age 75 and 80 years and followed through medical records at age 85 years.
• Researchers collected and analyzed blood samples to detect anti-HSV and anti-HSV-1 immunoglobulin (Ig) G, anti-cytomegalovirus (CMV) IgG, anti-HSV IgM, and anti-HSV and anti-CMV IgG levels and apolipoprotein ɛ4 (APOE 4) status of participants.
• Investigators collected information on anti-herpesvirus drug treatment and reviewed dementia diagnoses obtained from medical records to classify as established or probable dementia or Alzheimer’s disease (AD).

TAKEAWAY: 

• 82% of participants were anti-HSV IgG carriers, of which 6% had received drug treatment for herpes virus, and 7% of participants developed all-cause dementia and 4% AD during the median 15-year follow up.
• Anti-HSV IgG positivity was associated with double the risk of dementia (adjusted hazard ratio [aHR], 2.26; P = .031) but was not significantly associated with AD risk.
• In HSV and HSV-1 subsamples, treatment for herpes virus was not significantly associated with lower risks of AD (HR, 1.46, P = .532 and HR, 1.64; P = .419, respectively) or dementia (HR 1.70; P = .222 and HR, 1.60; P = .320, respectively).
• There was no significant interaction between anti-HSV IgG seroprevalence and APOE 4 with regard to dementia risk, likely due to underpowering, and there were no associations between anti-CMV IgG positivity or anti-HSV IgM positivity and AD or dementia.

IN PRACTICE:

“What’s special about this particular study is that the participants are roughly the same age, which makes the results even more reliable since age differences, which are otherwise linked to the development of dementia, cannot confuse the results,” lead author Erika Vestin, a medical student in the Department of Public Health and Caring Sciences, Clinical Geriatrics, Uppsala University, Sweden, said in a press release. Findings may drive dementia research further towards treating the illness at an early stage using common anti-herpes virus drugs, Vestin added.

SOURCE:

The study, with Vestin as lead author, was published online on February 14, 2024, in the Journal of Alzheimer’s Disease.

LIMITATIONS:

The study underrepresented people with diabetes, congestive heart failure, and stroke and lacked information on treatment compliance, dosage, and length and number of prescriptions, which prevented analysis of dose dependency. Since dementia data collection relied on medical records, dementia cases may be underreported. Some cases of AD could have been misclassified as vascular dementia or other dementia. 

DISCLOSURES:

The study was supported by the Gun and Bertil Stohne’s Foundation, Swedish Dementia Association, Swedish Society of Medicine, Märta Lundqvist Foundation, Thureus Foundation, Region Uppsala, Gamla Tjänarinnor Foundation, and Swedish Brain Foundation. The authors had no relevant conflicts of interest.