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Smoking is the best-known risk factor for chronic obstructive pulmonary disease (COPD), a debilitating lung condition that can severely limit a person鈥檚 day-to-day activities. But curiously, only a minority of lifelong smokers develops the disease, while non-smokers represent more than 25% of all COPD cases. A new study published today in The Journal of the American Medical Association聽suggests that a developmental mismatch between airway and lung size鈥攁 condition called dysanapsis鈥攃ould answer why.