Severity of adult onset asthma – a matter of blood neutrophils and severe obesity?

Abstract

<b>Background:</b> Associations between severe asthma and high body mass index (BMI), blood eosinophils (eos), neutrophils (neu) and fractional exhaled nitric oxide (FeNO) are rarely described in individuals with adult onset asthma. <b>Aim:</b> To study if high BMI, FeNO and blood eosinophils and neutrophils associate to severe asthma, in individuals with adult onset asthma. <b>Methods:</b> Postal surveys were performed in population samples from Northern Sweden in 2016. Participants were invited in 2019-2020 to follow-ups with structured interviews, spirometry, FeNO-test, skin prick test and blood sampling. N=251 with asthma onset ≥15 years of age participated. BMI was grouped as underweight (&lt;18.5), normal weight (18.5-24.9), overweight (25.0-29.9), obesity (30.0-34.9) and severe obesity (≥35). Severe asthma (SA) was defined as daily use of GINA step 4-5 treatment, uncontrolled SA was defined by report of severe exacerbations or asthma control test score &lt;20 and non-severe asthma as not using GINA step 4-5 treatment. <b>Results:</b> In total 66.1% were women, mean age was 62.7y, mean FeNO 18.4ppb, mean eos 0.21x109/L, mean neu 3.78x109/L, 40.6% were overweight, 25.9% obese and 10.8% severely obese. N=47 had SA whereof 23 had uncontrolled SA. There were no differences in smoking, allergic sensitization, FeNO or eos between SA and non-severe asthma. In SA, 36% had FEV1&lt;80% of predicted, vs 21% in non-severe asthma. Neutrophil levels in blood were higher in both SA and uncontrolled SA than in non-severe asthma. Severe obesity was more common in uncontrolled SA (26.1%) than in non-severe asthma (9.3%). <b>Conclusion:</b> Higher blood neutrophil levels and severe obesity were more common in severe than in non-severe adult onset asthma.