Asthma-COPD overlap: when a patient doesn't fit cleanly into either diagnosis

Asthma and COPD are taught as distinct diagnoses — asthma reversible and allergy-driven, COPD progressive and smoking- or exposure-driven — but a substantial share of people with chronic airway disease, particularly older adults with a smoking history and a childhood asthma diagnosis, have features of both simultaneously. Clinicians increasingly describe this as asthma-COPD overlap rather than forcing a single label, because the overlap population behaves differently: more exacerbations, more symptom burden, and a different response to treatment than either 'pure' diagnosis predicts.

The overlap is suspected when a patient has the fixed airflow obstruction that defines COPD on spirometry, plus features more typical of asthma — significant bronchodilator reversibility, elevated blood eosinophils, or a strong allergic and childhood asthma history. Getting the label right matters clinically: the type-2 inflammatory signature common in overlap patients means they're often better candidates for inhaled corticosteroids and, in more severe cases, the same biologic drugs used for eosinophilic asthma — treatments that plain COPD guidelines don't emphasize as strongly.

Managing overlap in practice usually means combining COPD-style bronchodilator therapy with asthma-style anti-inflammatory treatment more aggressively than either guideline alone would suggest, and checking eosinophil counts as part of routine follow-up rather than only at diagnosis, since that number helps steer whether escalating to a biologic makes sense.

Anyone with a COPD diagnosis who also had childhood asthma, has strong allergy history, or notices dramatic day-to-day symptom swings that pure COPD doesn't usually produce is a reasonable candidate to specifically ask their pulmonologist about overlap — it can change the treatment plan meaningfully, and eosinophil testing is a simple blood draw that clarifies the picture.