A disease linked to chickenpox has been found to increase the risk of stroke by 50 percent for three months in adults aged 50 and over. Older adults were found to have an increased risk of stroke after having the disease called shingles.

Shingles, or herpes zoster, is a disease triggered by the reactivation of the chickenpox virus varicella zoster (VSV), which could cause a painful skin rash. The viral disease could affect anyone who has had chickenpox, but older adults and people who have weak immune systems are at high risk of acquiring the disease.

The report, published by the Mayo Clinic Proceedings, states that patients have an increased risk of stroke by up to 50 percent for three months after having shingles. In addition, those who have had the disease also had more risk factors for stroke compared with those who had not not.

The chickenpox virus infects over 95 percent of the world's adult population. The researchers said that about one third of the infected patients will possibly develop shingles.

Earlier studies in Europe and Asia have shown that patients do have an increased risk of stroke and myocardial infarction (MI) after shingles. The current study focused on the risk of stroke and MI in the US population.

Nearly 5,000 adults over 50 who had shingles were matched with a group of age- and sex-matched individuals who had no history of the disease. Researchers measured the risks for stroke and MI separately.

Patients who previously experienced stroke were not involved in the stroke analyses, while those who experienced MI were excluded from the MI analyses. Researchers assessed the short-term risk of stroke and MI at three months, six months, one year and three years after shingles.

Results show that shingles is significantly associated with an increased risk of stroke for three months, said lead researcher Barbara Yawn from the Department of Research, Olmsted Medical Centre. No strong link between the disease and MI was found in the same period.

"There did appear to be a small increased risk for MI, but when you take other risk factors into consideration, it disappears," Yawn said. However, the risk of stroke and MI did not increase beyond three months after shingles.

Yawn said the link between stroke and shingles could be the consequence of the inflammatory response that occurs in the presence of acute zoster episode. However, the risk could be prevented by vaccine against shingles.

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