MONDAY, June 13, 2022 (HealthDay News) — Herpes zoster is not associated with increased dementia risk and may be associated with a small decrease in risk, according to a study published online June 8 in Neurology.
Sigrun Alba Johannesdottir Schmidt, M.D., Ph.D., from Aarhus University Hospital in Denmark, and colleagues examined the association between zoster and dementia during 1997 to 2017 using data from linked nationwide Danish registries. Data were included for 247,305 people aged 40 years and older with zoster and 1,235,890 matched general population comparators.
The researchers found that compared with matched comparators, the hazard ratio for all-cause dementia among people with zoster was 0.98 (95 percent confidence interval, 0.92 to 1.04) and 0.93 (95 percent confidence interval, 0.90 to 0.95) during the first year and thereafter, respectively. By the end of follow-up, dementia was diagnosed in 9.7 and 10.3 percent of zoster patients and matched comparators, respectively. Similar associations to those for all-cause dementia were seen in an analysis of Alzheimer disease as an outcome.
“We were surprised by these results. The reasons for this decreased risk are unclear, but it could be explained by missed diagnoses of shingles in people with undiagnosed dementia,” Schmidt said in a statement. “Shingles vaccination is encouraged for older people because it can prevent complications from the disease, but our study suggests it is unlikely to reduce dementia risk.”
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