Shingles Is Still Causing Dementia

We've written before in this blog ... and in Beating the Dementia Monster ... that there is a correlation between episodes of shingles with the development of dementia.  Shingles is caused by the herpes zoster virus which also causes chicken pox.  In fact, shingles is probably caused by the herpes zoster virus living in the body after a childhood chicken pox infection.

This topic is interesting to me because I don't have many risk factors for Alzheimer's disease.  But I did have shingles several times over the years; at least three times.  So maybe that explains my disease.

There was a new study published in August in the journal Alzheimer's Research and Therapy.  It reported on research with almost 150,000 subjects in three large cohorts of medical professionals.  Researchers followed them over decades, beginning as long ago as 1976.  Consistent with other research, they found a correlation between shingles events and the onset of dementia.  Surprisingly (to me, at least) they found that, in the context of shingles infections, carrying the APOE ε4 gene variant affected men much more than women.  (The ε4 variant of the APOE gene is what 23andMe tests for when predicting your risk of developing Alzheimer's disease.  It's the strongest genetic risk factor for Alzheimer's disease, although there are many others.)

But how much did shingles infection affect risk of dementia?  With such a large sample size and such a long period of time, we should see some reliable answers to this question.  So what did they find?

The researchers found that a history of shingles infection raised the risk of dementia by about 20%.  That's actually kind of a lot when you think about it.  

They further wrote, "Findings from these three large independent cohorts of women and men suggest herpes zoster was associated with a higher long-term risk of subjective cognitive decline. The risk may be greater for the APOE ε4 allele carriers among men, but not among women. The relation did not differ among those with potentially immunocompromising conditions. The magnitude of the elevated long-term risk of [subjective cognitive decline] may potentially be reduced by [shingles] vaccination, but further study is needed."

Note that, loosely defined, "subjective cognitive decline" is cognitive decline concerning enough to the patient to cause him or her to seek medical advice.  Statistically, these people are more likely to be diagnosed with actual Alzheimer's disease.