Chronic obstructive pulmonary disease (COPD): secondary care data

Data on hospital discharges for patients admitted with COPD are held in the Scottish Morbidity Record (SMR01) database, which also includes linked data on deaths. The discharge data in SMR01 can be used as a surrogate to estimate COPD incidence, which refers to the number of new cases in a population in a given period of time. Incidence is defined here as the first admission due to COPD, or in the absence of admission, death due primarily to COPD based on a 10-year incidence look-back period.

Chart 1 shows COPD incidence in Scotland by sex from 2002/03 to 2022/23 using the European Standard Population for age standardisation. In 2022/23 COPD incidence in both sexes continued to rise after sharply declining in 2020/21 due to the COVID-19 pandemic. The annual increase in incidence of 12.3% to 112.4 cases per 100,000 in females was larger than the 7.9% rise to 109.7 cases per 100,000 in males. However, in both sexes, incidence remained lower than prior to the pandemic.

Despite annual fluctuations in estimates, incidence has decreased in the long term, with reductions of 34.1% and 10.2% reported in males and females respectively between 2002/03 and 2022/23. During this period sex-related differences in incidence have been eliminated, with the ratio of new cases in males to females decreasing from 1.3:1 to 0.98:1.

The decrease observed in 2020/21 can be explained by changes to the provision and use of healthcare services during the pandemic, with many facing barriers to accessing or being unwilling to access services. Additionally, as only deaths with a primary cause of death of COPD were counted, mortality in COPD sufferers due to COVID-19 has likely been excluded here. These statistics should therefore be treated with caution.

Patterns of COPD over time can be understood more clearly by examining incidence rates in different age groups. As shown in Chart 2, incidence increases with age in both sexes. This is caused by the progressive nature of COPD, with the underlying lung damage occurring as a result of long-term exposure to tobacco smoke or other pollutants, as well as the well-described lag in the onset of smoking-related diseases (Lopez, 1994).

In under 65s and those aged 65 to 84, incidence has consistently been comparable between the sexes. In over 85s, rates have converged, driven primarily by a reduction in males. This decrease can be attributed to declining smoking rates since the 1970s (see Smoking Data section for more information on smoking and COPD). A gradual increase in female over 85s is likely partially due to smoking rates peaking later in females than males (Lopez, 1994) and increased susceptibility to smoking-related morbidity in females (Zysman & Raherison-Semjen, 2022).

More information on COPD incidence can be found in the ScotPHO profiles tool.