Background There is increased interest whether aetiology and co-morbid airways disease influence bronchiectasis disease severity.

Methods We conducted a retrospective study of 400 patients attending a specialist bronchiectasis clinic in NHS Lothian, Edinburgh, UK between May 2013 and September 2014 and using multivariable models we identified independent risk factors that influenced bronchiectasis disease severity using the Bronchiectasis Severity Index. We adjusted for age, sex, smoking history, aetiology and presence of co-morbid airways disease (asthma and COPD).

Results 400 patients were included in this study. The mean age was 66.0 (13.9) years. 253 (63.2%) were female. The majority (77%) had idiopathic (53%) or post infective bronchiectasis (24%). Other aetiologies were: allergic bronchopulmonary aspergillosis 8%; immune/auto-immune 6%; interstitial lung disease 3%; ciliary defects 3%; and inflammatory bowel disease 3%. Co-existing airways disease was common but not the predominant diagnosis (36% had asthma and 19% COPD).

Independent risk factors for severe bronchiectasis (BSI ≥ 9) were age 70–79 (OR 6.3, p = 0.003), age 80 and above (OR 7.3, p = 0.003) and smoking (OR 1.02, p = 0.002). It was not influenced by presence of airways disease or aetiology.

Conclusion In conclusion, neither aetiology nor presence of airways disease was independent risk factors for severe bronchiectasis severity. Age was the strongest independent predictor for severe bronchiectasis severity.