BACKGROUND During the 80s and 90s the mortality and number of hospitalisations due to chronic obstructive pulmonary disease (COPD) in the country of Denmark almost doubled. Since then there has been a plateau. OBJECTIVE To analyse age, period, and cohort effects on rates of deaths and first-time hospitalisations with COPD in Denmark during the period from 1994 to 2012 and to make a forecast of these parameters. METHODS By use of national registers, two separate age-period-cohort analyses were made, one on COPD-specific mortality rates and the other on incidence rates of first-time hospitalisations with COPD. RESULTS Both analyses found that high risk of developing severe COPD is associated with being born for women around year 1930 and for men around year 1925. The model has solid predictive ability and projections of future death- and hospitalisation rates due to COPD were made. CONCLUSION Long-term cohort effects rather than present exposure and treatment explain the recent rise and fall in the epidemic of COPD in Denmark. In the near future ageing of birth cohorts with lower COPD-specific mortality and hospitalisation rates will most likely lead to a substantial decrease in severe COPD in Denmark. However, rising trends for cohorts born after year 1948 calls for concern.