Shingles Risk 70% Higher for Adults With Asthma

Marcia Frellick

January 06, 2016

Asthma is an unrecognized risk factor for herpes zoster (shingles) in adults, and clinicians should consider vaccinating asthmatics at least 50 years old as a target group, according to a study published online December 28 in the Journal of Allergy and Clinical Immunology.

Hyo Jin Kwon, MD, from the Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota, and the Department of Medicine of Catholic University of Korea in Seoul, and colleagues reviewed medical records for potential patients with shingles. They identified 371 cases with shingles during the study and compared them against 742 control patients.

Of the 371 shingles cases, 23% (87 people) had asthma compared with 15% (114/742) from the control group. The authors found that adults with asthma were at about a 70% greater risk of developing shingles compared with those without asthma (odds ratio [OR], 1.73; 95% confidence interval [CI], 1.26 - 2.39; P < .001). The population-attributable risk percentage for asthma was about 10%.

Adjusted for potential confounders identified from univariate models, the link between asthma and zoster remained significant (adjusted OR, 1.70; 95% CI, 1.20 - 2.42; P = .003).

This study builds on the researchers' previous work from 2013, which linked childhood asthma with an increased risk for shingles.

"This population-based study in adults upholds our previous finding on asthma as an independent risk factor for zoster in asthmatic children," the authors write. "This might also be true for other atopic conditions, such as atopic dermatitis. The effect of asthma on risk of infection might go beyond the airways."

The researchers also note that, with asthma and other atopic conditions accounted for, both asthma and atopic dermatitis were found to be independently linked with higher shingles risk. The shingles rate was 12% in patients with atopic dermatitis vs 8% of the controls.

Reasons for the connection are unclear, but impairment in immune function in the skin and airways has been well-documented in patients with asthma or atopic dermatitis, the authors say. They reason that because asthma helps suppress adaptive immunity, it may increase the risk for varicella zoster virus reactivation.

1 Million Shingles Cases a Year in the United States

Nearly 1 million cases of shingles occur every year in the United States, with an estimated one third of all adults affected by age 80 years.

The authors used Olmsted County, Minnesota, as the study population has unique advantages: Medical care is virtually self-contained within the community, and when patients register with any healthcare provider, they or their parents/guardians grant or refuse use of their medical records for research. More than 95% of all subjects grant authorization, the authors write.

However, the population's homogeneity may make it difficult to generalize results, Brad Spellberg, MD, chief medical officer at the Los Angeles County and University of Southern California Medical Center, told Medscape Medical News. The authors include the predominantly white and older population ("mostly born in the 1940s, when asthma incidence was low") as a limitation.

Case-control studies are hypothesis-generating, not hypothesis-confirming, Dr Spellberg noted. "Since there is no known biological basis for why asthma would affect shingles risks, other than corticosteroid use, which the authors claim to have ruled out, but cannot definitively rule out, the pretest probability that this is correct is rather low."

He added, "Only a prospective study, preferably with an intervention and a control group, rather than a cohort study, can confirm this."

David Thomas, MD, MPH, director of the Division of Infectious Diseases and professor of medicine at Johns Hopkins University School of Medicine in Baltimore, Maryland, told Medscape Medical News he agrees the results are premature and unlikely to change practice.

However, if randomized controlled trials confirm the asthma–shingles link and show that vaccinating earlier prevents shingles, preventing such a painful illness would likely be worth investigating the cost-effectiveness of the vaccine for the target group, he said.

He added that it was important that the authors addressed corticosteroid use of patients with asthma because steroids could have been the factor that causes the shingles, rather than the asthma.

"Inhaled corticosteroid...use was not shown to be a risk factor for zoster in our study population," the authors write.

The study was supported by the National Institute of Allergy and Infectious Diseases, the Scholarly Clinician Award from the Mayo Foundation, and the Rochester Epidemiology Project, which is supported by the National Institute on Aging of the National Institutes of Health. Dr Kwon receives research support from the National Institutes of Health, the National Institute of Allergy and Infectious Diseases, and the Scholarly Clinician Award from the Mayo Foundation. One coauthor receives research support from the Centers for Disease Control and Prevention and Merck; has received consulting fees from Merck, BI, Novartis, AstraZeneca, and GlaxoSmithKline; has received travel support from GlaxoSmithKline; and receives lecture fees from Miller Medical Communications and Annenberg Center. The other authors have disclosed no relevant financial relationships.

J Allergy Clin Immunol. Published online December 28, 2015. Abstract

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