People over the age of 50 who develop shingles have an increased risk of suffering a stroke over the next 90 days, a new study has found.

Shingles is a viral disease that affects the nerves and surrounding skin. It is caused by the herpes varicella-zoster virus, which also causes chickenpox. Once a person has had chickenpox, the virus lies inactive in their nervous system. If this virus becomes reactivated, it becomes shingles.

Symptoms include a painful, blistering rash on one side of the body.

Around 95% of the world's adult population has had chickenpox, leaving them at risk of developing shingles. Up to one-third will develop the illness at some point in their lives.

Previous studies have suggested an increased risk of heart attack and stroke after shingles, so US researchers decided to investigate further.

They assessed the risk of suffering a heart attack or a stroke in around 5,000 adults over the age of 50 who had a confirmed case of shingles. These were matched with similarly-aged peers who did not have shingles.

The risk of suffering a stroke or heart attack was assessed at three months, six months, one year and three years after having shingles.

The study found that those who developed shingles had a 50% increased risk of suffering a stroke over the next 90 days.

The researchers acknowledged that those who developed shingles tended to have more risk factors for stroke than those who did not develop shingles, ‘suggesting they had worse health overall'.

"However, the bottom line is that that shingles was still associated with an increased risk of stroke for three months afterwards even when we made allowances for these multiple risk and confounding factors," they emphasised.

The study did not find any strong link between shingles and suffering a heart attack.

"There did appear to be a small increased risk for heart attack, but when you take other risk factors into consideration, it disappears," they noted.

Furthermore, there was no increased risk of heart attack or stroke after three months had passed.

The researchers said there may be a number of reasons for these findings.

"Recent studies have shown that the zoster virus appears to affect vascular tissues as well as the central nervous system and that it may therefore be a systemic illness.

"Another possible explanation is that stroke is a consequence of the inflammatory response that occurs with an acute zoster episode. This increased risk of stroke may be preventable by vaccinating against the zoster virus," the team said.

Details of these findings are published in the journal, Mayo Clinic Proceedings.

For more information on shingles, click here