Clinical features and risk factors of intermediate-onset asthma.

Abstract

Background: Bronchial asthma can present with different features depending on the age of onset. While early and late onset asthma are well documented, intermediate-onset asthma is much less studied.

Aim: To investigate the impact of clinical characteristics and risk factors on asthma control in persistent asthma with a focus on intermediate-onset asthma.

Methods: In a cohort of 250 patients with persistent asthma (age: 54±16yrs) 3 clusters were defined: EA(early-onset asthma ≤12yr);IA (intermediate-onset asthma 12-40yr);LA (late-onset asthma >40yr). Medical history, smoking and occupational exposure, lung function, blood cell counts, body mass index (BMI), comorbidities, and level of asthma control were recorded.

Results: Among 250 patients 78(31%) had EA, 75(30%) IA and 98(39%) LA. Occupational exposure was significatively higher in IA than in EA and LA (62vs20vs39%;p=0.002) while smoking (39vs32vs37%), outdoor pollution (42vs44vs47%) and obesity (20vs17vs21%) were similar among groups. IA had more blood eosinophils than LA (4.5±3.5vs2.7±1.9%;p=0.005) and more neutrophils than EA (56±11vs 50±9%;p=0.04). In IA poor asthma control (ACT<20) was associated to occupational exposure (59vs25%;p=0.0004), smoking (66vs13%;p<0.0001) and obesity (53vs25%;p=0.003). Occupationally 82% were exposed to chemical dusts/vapour, 23% to metals, 17% to organic dusts, 13% to textiles with no gender differences. Poor symptom control was more frequent in subjects exposed to chemicals than in others (77%vs 50%;p=0.003).

Conclusions: Intermediate-onset asthma is a different phenotype in which obesity, occupational exposure, especially to chemical dusts, and smoke could have an important influence on disease mechanisms and symptom control.