A commentary in the Journal of Alzheimer’s Disease (Itzhaki 2018) highlights several new epidemiological studies from Japan that demonstrate increased risk of senile dementia in patients with acute herpesvirus infection. One group studied insurance records to identify 8,362 Taiwanese patients in their late 50’s or early 60’s who developed acute HSV1 infections in the year 2000. They also studied 25,086 age matched controls. Those with acute HSV1 infections were found to have a 2.6 fold increased risk of developing dementia. However, those treated aggressively with antiviral therapy had almost a 90% reduction in risk for dementia compared to those who went untreated (Tzeng 2018). Of note, most of the dementias in the HSV1 group study were not the common Alzheimer’s or vascular dementias, the most common forms.
The authors describe two other Taiwan studies published in the past year that studied the increased risk of senile dementia in senior patients who developed acute shingles or zoster opthalmicus infections (Tsai 2017, Chen 2018). These seniors had nearly a three-fold increase in risk of senile dementia, according to insurance records. One weakness of these studies is that the data came from insurance records and the patients were not evaluated for possible signs of dementia at the baseline, when they developed their herpesvirus infections.
Still, after decades of targeting amyloid beta with little success, these results combined with the new findings relating to HHV-6A, HHV-7 and HSV1 active transcripts in AD brains, have some scientists calling for a paradigm change. An excellent commentary on this subject can be found Cell Press ( Haas 2018).
HHV-6A appears to have a lower prevalence in Asia. In a recent study of Chinese patients and the risk of non-Hodgkin’s lymphoma, it was determined that the seroprevalence of HHV-6A in controls was only 11% (Bassig 2018).