Shingles and Chickenpox (Varicella-Zoster Virus) - Risk Factors

Risk Factors for Shingles (Herpes Zoster)

About 500,000 cases of shingles occur each year in the US. Anyone who has had chickenpox has risk for shingles later in life, which means that 90% of adults in the US are at risk for shingles. Shingles occurs, however, in between 10% and 20% of these adult over the course of their lives, so certain factors must exist to increase the risk for such outbreaks.

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The Aging Process. The risk for herpes zoster increases as people age, so the overall number of cases will undoubtedly increase as the baby boomer generation gets older. One study estimated that a person who reaches 85 has a 50% chance of having herpes zoster. The risk for postherpetic neuralgia (PHN) is also highest in older people with the infection and increases dramatically after age 50. PHN is persistent pain and is the most feared complication of shingles. An interesting, but small, 2003 study reported that older people with a history of chickenpox who practiced Tai Chi Chih experienced an increase in immune factors against herpes zoster. Tai Chi Chih is an Asian practice that employs balance, alignment, concentration, and meditation. Because Tai Chi and similar practices, such as yoga, reduce stress, these study results suggest that stress reduction techniques might be helpful in reducing the risk for herpes zoster.

Immunosuppression. People whose immune systems are impaired from diseases such as AIDS or childhood cancer have a risk for herpes zoster that is much, much higher than those with healthy immune systems. Herpes zoster in people who are HIV positive may be a sign of full-blown AIDS. The current drugs used for HIV, called protease inhibitors, may also increase the risk for herpes zoster. But drug-associated herpes does not appear to be as severe as it is in AIDS patients.

Cancer. Cancer places people at risk for herpes zoster. At highest risk are those with Hodgkin's disease (13% to 15% of these patients develop shingles). About 7% to 9% of patients with lymphomas, and between 1% and 3% of patients with other cancers, have herpes zoster. Chemotherapy itself increases the risk for herpes zoster.

Immunosuppressant Drugs. Patients who take certain drugs that suppress the immune system are at risk for shingles (as well as other infections). They include:

Azathioprine (Imuran).
Chlorambucil (Leukeran).
Cyclophosphamide (Cytoxan).
Cyclosporine (Sandimmune, Neoral).
Cladribine.

These drugs can be used in patients who have undergone organ transplantation, but they are also often used for severe autoimmune diseases caused by the inflammatory process. Such disorders include rheumatoid arthritis, systemic lupus erythematosus, diabetes, multiple sclerosis, Crohn's disease, and ulcerative colitis.