London School of Hygiene & Tropical Medicine

The research, published in PLOS Medicine, showed the risk is greatest during the early stages of shingles, with a 2.4 fold increase in the rate of stroke and a 1.7 fold increase in the rate of heart attacks in the first week after shingles, compared to time periods when the patient did not have recent shingles. The study also highlighted that risk levels returned to normal within six months.

Identifying when patients with shingles are most susceptible will support doctors and healthcare professionals to provide early intervention through closer monitoring of these individuals at times of increased risk - potentially reducing cases of heart attack and stroke.

Shingles, caused by the reactivation of the chickenpox (varicella-zoster) virus, causes a blistering rash on the skin. It mostly affects adults over the age of 50 and can lead to post-herpetic neuralgia, in which severe nerve pain lasts for more than three months after the rash has gone.

The research group has previously demonstrated an increase in stroke risk after shingles in the UK population. In the new study, the researchers used data from the United States to identify 42,954 patients with shingles aged 65 years or over who had had a stroke and 24,237 patients with shingles who had suffered a heart attack during a five-year period. They compared the risk of stroke and heart attack for individuals during a 12 month period after shingles relative to periods when the individual did not have recent shingles.

Lead author Caroline Minassian, Research Fellow in Epidemiology at the School, said: "Shingles affects around one million Americans and 200,000 people in the UK each year. The condition, which affects mainly older people, can be very irritating and extremely painful and has been linked to more acute health problems.

"Our findings show an increased risk of both heart attack and stroke up to three months after shingles diagnosis, with the greatest risk being observed in the first week.  The study builds on the existing evidence and crucially highlights when patients may be most vulnerable - if we know when these events are more likely to happen this may potentially help to prevent heart attacks and stroke in older people."

Another key aspect of the study was that the researchers had access to data on shingles vaccination. This allowed them to compare the risk of stroke and heart attack after shingles among vaccinated and unvaccinated individuals. They found no evidence to suggest that those who had not been vaccinated were more susceptible to stroke or heart attack.

Dr Minassian said: "Low vaccination rates in our study means more research is needed to assess whether vaccination reduces vascular risk after shingles. However, our results show clearly that the risk of stroke and heart attack is increased for a short time after shingles."

The researchers used the self-controlled case series method, in which they looked at individuals' risk of stroke and heart attack, comparing each patient's risk following shingles, to when they did not have recent shingles.  This means the results are not affected by inherent differences in vascular risk between those who get shingles and those who do not.

The authors note that while Medicare data include high quality information on demographics, clinical encounters and prescription drugs it is administrative data. Misclassification of exposures and outcomes is therefore possible.

This research was carried out in collaboration with Kings College London and was supported by the National Institute for Health Research (NIHR), Stroke Association and the Wellcome Trust.

The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health.

Publication

• Caroline Minassian, Sara Thomas, Liam Smeeth, Ian Douglas, Ruth Brauer, Sinéad Langan, Acute Cardiovascular Events after Herpes Zoster: A Self-Controlled Case Series Analysis in Vaccinated and Unvaccinated Older Residents of the United States. PLOS Medicine. DOI: 10.1371/journal.pmed.1001919