Reacción a "Reactions: pre-publication claims part of dementia cases are caused by herpes-like viruses"

This was an interesting study that used a unique approach to study the effect of the shingles vaccine in preventing a new diagnosis of Alzheimer's disease. They took advantage of the specific birth date eligibility of the shingles vaccine to the elderly population of Wales and used a regression discontinuity analysis to compare the prevalence of dementia in individuals older versus younger than that specific cutoff. This is distinct from many other studies that compare individuals who were eligible for the vaccine and either received or did not receive the vaccine, the interpretation of which can be complicated by other factors that may affect the demographics of the population that receive the vaccine versus those that do not.

There are a few important limitations to this study: First, the diagnosis of Alzheimer's dementia versus other dementias was not well defined, so whether this effect is specific to Alzheimer's disease will need further analysis. Perhaps a more important limitation is that the study really focused on individuals who were 79 to 80 years old, which is a relatively old demographic for Alzheimer's disease studies, especially for preventing new diagnoses.