Does severe shingles increase the risk for dementia?

The 2 minute update looks at a study regarding dementia rates in people who had severe shingles and people who did not – are people who have severe shingles more likely to be diagnosed with dementia?

This is a retrospective cohort study done in Italy, and it included over 132,000 people. A little over 12,000 people at least age 50 were hospitalized due to herpes zoster. 

Those 12,000 patients were matched with over 60,000 who were hospitalized for a different reason, and another 60,000 who were just in the general population. I like that design, since it includes the question if the hospitalization or the reason for the hospitalization is potentially the issue. The data came from a registry that had 23 years of data.

The bottom line is that the people hospitalized with shingles were 13% more likely to be diagnosed with dementia compared with the general population, and 8% more likely than people hospitalized for a different reason. Both of those are statistically significant.

Prior studies have not shown that developing shingles is associated with an increased risk of dementia, but most of the ones that I found were not looking specifically at cases severe enough to require hospitalization. Perhaps only those with severe cases are at increased risk of cognitive decline. However, there’s also a study that demonstrates that being vaccinated against herpes zoster probably decreases one’s risk of developing dementia. I did not cover that study because the statistics are really complicated, and this is the 2 minute update not the 12 minute update, but I’ll include it in the reference.

No one wants shingles, and the current vaccine is about 90% effective at preventing cases in people over 70, and even more effective in younger patients. And maybe it decreases the risk of developing dementia. Personally, within a few weeks of turning 50 I received my first dose of Shingrix, which is the only shingles vaccine on the market right now, and I was back two months later for the second dose. I’m glad I did that.

Reference: Blandi et al. Herpes zoster as risk factor for dementia: a matched cohort study over 20 years in a 10-million population in Italy. J Prev Alzheimers Dis. 2025 April 12; Online ahead of print

Pomirchy et al. Herpes Zoster Vaccination and Dementia Occurrence. JAMA 2025 April 23; Online ahead of print