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Shingles are the reactivation of the chickenpox virus but according to the CDC, nobody really knows what triggers the reactivation: “Scientists aren’t sure why the virus can reactivate years later, causing shingles.”[i]

There are, however, a surprising number of diseases, conditions, and pharmaceuticals that appear to increase the risk for shingles, from aging to psoriasis and chemotherapy. Most of them seem to have a common denominator – a weakness in the immune system.

Common Risk Factors for Herpes Zoster

1.     Age

Advanced age increases the risk of developing shingles and by the time you get to age 85, the chance of getting it is fifty-fifty.[ii] Additionally, older people tend to suffer more complications. This might be from immunosenescence – the gradual decline in immunity associated with increasing age.

2.     Immunosuppression

Diseases that compromise the immune system, like cancer, AIDS, diabetes, leukemia, chronic kidney disease, inflammatory bowel disease (IBD), multiple sclerosis,  and lymphoma increase the risk of shingles, as do immunosuppressive medications for things like rheumatoid arthritis and bone marrow and organ transplants. Drugs like corticosteroids, chemotherapy, and transplant-related immunosuppressive medications are also associated with shingles.

3.     Being female

In a recent prospective study, researchers found that herpes zoster was significantly associated with being female. [iii] They examined the data on more than 27 million individuals and out of almost a million diagnosed shingles cases, 62% were women.

Autoimmune diseases also affect more women than men. All of this could be attributed to hormonal fluctuations, especially during pregnancy and menopause, both of which can trigger immune-related diseases such as diabetes. Researchers have noticed an association between both pregnancy and menopause and autoimmune diseases.

4.     Micronutrient deficiencies

The efficient functioning of the immune system is heavily dependent on optimal nutrition. Two of the most important nutrients for immune function are vitamins C and D. Vitamin C deficiency means weakened immunity and therefore a higher susceptibility to infections, including viral one like herpes zoster.

Almost every tissue type in the body has receptors for vitamin D and it has a profound effect on the immune system.  “Considering the importance of vitamin D in host immunity, we hypothesize that vitamin D acts as an effect-modifier for the entire herpes zoster spectrum with regard to disease susceptibility, manifestation, the efficacy of pharmacologic management, and emergent complications during treatment.” [iv]

5.    Declining Immunity to VZN

“This reactivation occurs when immunity to VZV declines because of aging or immunosuppression.”[v]

Shingles occur when cell-mediated immunity to chickenpox wanes and drops below a certain level. With age, the memory of immune cells can decrease along with the decline in mental memory.

Ironically, the chickenpox vaccine has been linked to an increase in shingles. Adults who previously contracted chickenpox in their youth can get a natural “booster” shot to their immunity to varicella-zoster by contact with children with chickenpox. The vaccine has changed all of this.

“Mass use of the chickenpox vaccine by children has eliminated the opportunity for natural asymptomatic boosting of immunity in adults and left adults vulnerable to shingles later in life.”[vi]

6.     Depression

Depression seems to increase the risk of shingles. A population-based case-control study of subjects in Denmark and the United Kingdom concluded: “mood disorders were associated with an increased risk of zoster.”

The authors of the study write: “Zoster is caused by reactivation of the varicella-zoster virus (VZV) from sensory ganglia when cell-mediated immunity (CMI) wanes below a critical level. Mood disorders, such as depression and anxiety, have been associated with impaired CMI. In particular, it has been demonstrated that VZV-specific CMI is reduced in major depression and is negatively associated with severity.”[vii]