COMMENTARY

New Cause Eyed for Adult-Onset Asthma

Nicholas Gross, MD, PhD

Disclosures

February 20, 2015

New Risk Factors for Adult-Onset Incident Asthma. A Nested Case-Control Study of Host Antioxidant Defense

Larkin EK, Gao YT, Gebretsadik T, et al
Am J Respir Crit Care Med. 2015;191:45-53

Study Summary

Asthma typically begins early in life but occasionally it begins in adulthood, sometimes in middle life or even later.

The risk factor(s) for adult-onset asthma have been puzzling. It is rarely due to atopy.[1] The possibility that antioxidants or their deficiency may play a role has been tested but so far remains unsubstantiated.[2]

An appropriately designed and powered study now shines some new light on the antioxidant theory of adult-onset asthma.

The question posed by Larkin and colleagues was whether a deficit in plasma biomarkers of antioxidant host defense precedes onset of adult asthma.

A nested case-control study was carried out on 65,372 women in Shanghai, China, with a mean age of 52 years.

The study subjects had no history of previous asthma. Baseline urinary F2-isoprostanes, plasma concentrations of antioxidant micronutrients (tocopherols, xanthines, carotenes, and lycopene), and antioxidant enzyme activity (platelet-activating factor acetylhydrolase [PAF-AH] and superoxide dismutase) were measured at enrollment.

The women were followed for a mean of 7.5 years. During this time, 150 developed asthma, which was confirmed both by symptoms and either methacholine challenge or beta-agonist reversibility. The investigators matched these asthma subjects at a ratio of 1:2 with 299 of the control subjects from the same cohort who had not developed asthma.

The levels of the various antioxidants as measured at trial onset in the two groups were then compared. Investigators found that, compared with the control group, the adult-onset asthma subjects had significantly lower levels of alpha-tocopherol and PAF-AH. Other antioxidant biomarker levels were not different between the two groups. The authors suggest that deficiencies of the two aforementioned antioxidant biomarkers are risk factors for the subsequent development of adult-onset asthma.

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