Iceland COPD was defined broadly and included diagnoses of chronic bronchitis or emphysema made between 1980 and 2011 at the Landspitali University Hospital. A total of 8246 subjects born between 1883 and 1964 were included, with most (5871) of the confirmed COPD diagnoses made during the years 1998–2011. The actual age at onset of COPD is difficult to assess, as patients have usually had signs and symptoms for a long time before admission to hospital. To define an early-onset group we used year of birth as a surrogate, using the group born between 1940 and 1964 (N=1470) representing the youngest 19.6% of patients. Association analyses were based on 3857 chip-typed cases, and 3639 patients with at least one first- or second-degree relative chip-typed.
