Comorbid conditions associated with increased herpes zoster risk in younger patients

A range of conditions were associated with an increased risk of herpes zoster, especially immunosuppressive conditions, and the increased risk was greater in younger age groups, a study found.

Researchers conducted a case-control study among 144,959 adults diagnosed with zoster between 2000 and 2011 and compared them to 549,336 controls matched by age, sex, and practice (to control for practice-level socioeconomic status).

Results appeared online May 13 at BMJ.

The researchers examined the following risk factors of interest: rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease, chronic obstructive pulmonary disease, asthma, chronic kidney disease, depression, and diabetes (overall and by type). Severely immunosuppressive conditions were the strongest risk factors for zoster, although their overall prevalence was low—applying to only 2.8% of zoster patients and 1.2% of control patients. Among the risk factors of interest, systemic lupus erythematosus had the strongest relative risk of zoster (adjusted odds ratio, [OR] 1.72, 99% CI, 1.45 to 2.04) but the condition was very rare (0.3% of cases and 0.1% of controls). Other conditions that had an association included lymphoma (OR, 3.90, 99% CI, 3.21 to 4.74) and myeloma (OR, 2.16; 99% CI, 1.84 to 2.53). The researchers noted that patients with these conditions are not eligible for zoster vaccination.

The odds ratios for some of the other risk factors of interest were 1.46 (99% CI, 1.38 to 1.55) for rheumatoid arthritis, 1.36 (99% CI, 1.26 to 1.46) for inflammatory bowel disease, 1.32 (99% CI, 1.27 to 1.37) for chronic obstructive pulmonary disease, 1.21 (99% CI, 1.17 to 1.25) for asthma, 1.14 (99% CI, 1.09 to 1.18) for chronic kidney disease, and 1.15 (99% CI, 1.10 to 1.20) for depression. Although no association existed between zoster and diabetes overall (OR, 1.02; 99% CI, 0.99 to 1.05), there did appear to be an association with type 1 diabetes (OR, 1.27; 99% CI, 1.07 to 1.50).

The relative effects of many of the risk factors were larger in younger patients, the authors noted. After excluding severely immunocompromised patients, researchers calculated the predicted risk of zoster on the basis of the patients' risk factor profiles. For 97,789 zoster cases among patients younger than 70 years old, 3,619 (3.7%) had a predicted risk as high as that for the general population aged 70 or over, and 643 (0.96%) of 67,000 patients younger than 60 years old had a predicted risk as high as those age 60 to 69 years.

“What this study has highlighted, however, is that the strongest clinical risk factors for zoster are contraindications to its vaccine; the people arguably in most need of protection against zoster cannot currently benefit from vaccination,” the authors wrote. “Alternative risk reduction strategies in these patients would help those at greatest risk of this disease and its complications.”