Trends in COPD mortality from 1983 to 2018: protocol for a population-based cohort study in Denmark

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death worldwide, which is partly contributed to the increasing prevalence of COPD owning to a demographic shift towards an older population. Conversely, recent studies on COPD mortality that take this demographic shift in age into account find decreasing overall age-standardised COPD mortality rates over time. This decrease in the age-standardised COPD mortality rate is contributed advances in COPD diagnostics and treatment, decreasing smoking prevalence and general advances in medical care particularly in western countries. However, it is unknown if patients with COPD have experienced a comparable relative increase in survival in line with the general population.Hence, there is a need for longitudinal studies comparing trends in mortality in patients with COPD compared with matched non-COPD individuals from the background population.

This is a cohort study with a matched non-COPD comparator cohort. Data are retrieved from the Danish national registers. Data from multiple registries from 1983 to 2018 will be merged on an individual level using the 10-digit Civil Registration numbers that are unique to each citizen in Denmark. Time trends in mortality in patients with COPD compared with the matched comparator cohort will be examined in three study periods: 1983-1993, 1994-2007 and 2008-2018.

The study is entirely based on registry data and ethical approval is not required according to Danish Law and National Ethics Committee Guidelines. The results will be published in peer-reviewed journals and reported at appropriate national and international conferences.