Previous research has suggested that children with asthma are at increased risk for developing herpes zoster (shingles or zoster), but this association has not been assessed in adults. Recent estimates show that asthma affects up to 17% of the United States population, and shingles affects nearly 1 million Americans every year, particularly the older adult population. For a study published in the Journal of Allergy and Clinical Immunology, Young J. Juhn, MD, MPH, and colleagues sought to determine whether or not asthma is associated with an increased risk of zoster in older adults.
Making the Link
Prior to the current study, Dr. Juhn and colleagues found that asthma was linked to an increased risk of various respiratory infections, including community-acquired pneumonia, whooping cough, and ear infections. “Although this research was helpful, it didn’t explain whether the associations were due to airway structure or issues surrounding immune function,” says Dr. Juhn. “For the new study, we analyzed the association between asthma and zoster, which is not an airway infection, in order to help determine the epidemiologic relationship between asthma and the risk of zoster.”
For the analysis, researchers compared the frequency of asthma among adults aged 50 or older with zoster with that of age- and gender-matched controls who did not have a history of zoster. Asthma status was based upon predetermined criteria rather than having physicians diagnose the disease using ICD-9 codes or self-reported asthma status, according to Dr. Juhn.
Of the 371 patients with shingles, 23% had a history of asthma, compared with a rate of 15% that was observed among the 742 control subjects, Dr. Juhn says. “Asthmatic patients had about a 70% higher risk of developing zoster than non-asthmatic patients,” he adds. “However, it’s important to note that although asthma was associated with an increased risk of zoster, asthma treatment—and inhaled corticosteroids, in particular—was not associated with zoster risk. Medication did not account for the association between asthma and risk of zoster. Our study results suggest that the impact of asthma on susceptibility to microbial infections goes beyond the airway and affects cell-mediated immune function.”
From a clinical practice standpoint, Dr. Juhn suggests that the study findings point to the need for patients and clinicians to be aware of asthma as a previously unrecognized risk factor for zoster. “Because asthma treatment did not account for this association, clinicians and patients should not be concerned about any potential implications of asthma treatment on the risk of zoster,” he says. “However, given our findings, the fact that the FDA has approved the zoster vaccine for adults older than age 50, and because asthma affects a large proportion of the adult population, individuals with asthma should be vaccinated against zoster. The Advisory Committee on Immunization Practices recommends the zoster vaccine for patients aged 60 and older, but physicians should also consider this vaccination for patients aged 50 or older with a history of asthma.”