Characteristics of non-smoking adult asthma patients with chronic airflow limitation.
OBJECTIVE
Chronic airflow limitation (CAL) can develop in a subgroup of patients with asthma. Characterising these patients is important because reduced lung function is a risk factor for adverse asthma outcomes. We hypothesised that heterogeneity in patients with CAL may be influenced by age at asthma onset. We first compared never-smoking asthma patients with and without CAL, and subsequently examined the differences between patients with late and early-onset asthma within the CAL cohort.


METHODS
Patients seen in our hospital's respiratory clinic between 1 Jan 2015 and 31 December 2015 were recruited to the study. CAL was defined as post-bronchodilator forced expiratory volume in 1 second (FEV1)<80% predicted, in the presence of post-bronchodilator ratio <70%. Variables independently associated with CAL were determined using a multivariate logistic regression model. Comparisons between patients with late-onset asthma (age ≥18 years) and early-onset asthma were made within the CAL cohort.


RESULTS
247 patients were included in the study. Age was the only variable independently associated with CAL after regression analysis, with an increase in odds of 3.8% (95% CI 0.4-7.3%) for every 1 year increase in age, p = 0.027. 63.2% of patients with CAL had late-onset asthma. Compared to patients with early-onset asthma, those with late-onset asthma had higher fractional exhaled nitric oxide levels (43 ± 32 ppb vs 20 ± 8 pb, p = 0.008).


CONCLUSIONS
An increase in age is associated with CAL in never-smoking asthma patients. In addition, age at asthma onset appears to influence airway inflammation in patients with CAL.
a Department of Respiratory and Critical Care Medicine , Changi General Hospital , Singapore , Singapore.
TunnRen
T
Tay
a Department of Respiratory and Critical Care Medicine , Changi General Hospital , Singapore , Singapore.
Xuening
X
Choo
a Department of Respiratory and Critical Care Medicine , Changi General Hospital , Singapore , Singapore.
Rosna
R
Ihsan
a Department of Respiratory and Critical Care Medicine , Changi General Hospital , Singapore , Singapore.
Hsiao Peng
HP
Toh
a Department of Respiratory and Critical Care Medicine , Changi General Hospital , Singapore , Singapore.
Hang Siang
HS
Wong
a Department of Respiratory and Critical Care Medicine , Changi General Hospital , Singapore , Singapore.
Augustine
A
Tee
D000328:Adult; D017677:Age Distribution; D017668:Age of Onset; D000368:Aged; D018927:Anti-Asthmatic Agents / Q000627:therapeutic use; D001249:Asthma / Q000188:drug therapy / Q000453:epidemiology* / Q000503:physiopathology*; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology* / Q000503:physiopathology*; D044469:Racial Groups; D012129:Respiratory Function Tests; D012307:Risk Factors
D018927:Anti-Asthmatic Agents
Eosinophils; fractional exhaled nitric oxide; late onset