Provided is a method for generating an assessment of a respiratory disease in a subject at a current point in time. The method comprises determining a baseline statistic relating to usage of an inhaler in a baseline period. The inhaler is configured to deliver a rescue medicament to the subject, and has a use determination system configured to determine usage of the inhaler by the subject. The method also comprises determining a current statistic relating to usage of the inhaler in a current period containing the current point in time. The method further comprises generating a comparator variable. Generating the comparator variable comprises comparing the current statistic and the baseline statistic. The assessment of the respiratory disease is based on the comparator variable.