Increasing severity of chronic obstructive pulmonary disease (COPD) is associated with increasing risk of poor outcomes. Using health registry data, we aimed to assess the association between treatment intensity levels (TIL), as a proxy for underlying COPD severity, and long-term outcomes.

Using Danish nationwide registries, we identified patients diagnosed with COPD during 2001–2016, who were alive at index date of 1 January 2017. We stratified patients into exclusive TILs from least to most severe: no use, short term therapy, mono-, dual-, triple therapy, oral corticosteroid (OCS), and long-term oxygen treatment (LTOT). Survival analyses were used to assess 5-year outcomes by TIL.

We identified 53,803 patients with COPD in the study period (median age: 72 years [inter quartile range, 64–80], 48 % male). The three most severe TILs were associated with a significant incremental increase in all-cause mortality with an adjusted hazard ratio (aHR) for triple therapy, OCS and LTOT of 1.44 (95 % CI: 1.38–1.51), 1.67 (95 % CI: 1.59–1.75), and 2.91 (95 % CI: 2.76–3.07) compared with those receiving no therapy as reference. The same pattern was evident for the composite outcome of 5-year mortality or COPD-related hospitalization with an aHR for triple therapy, OCS and LTOT of 2.30 (95 % CI: 2.22–2.38), 2.85 (95 % CI: 2.74–2.96), and 4.00 (95 % CI: 3.81–4.20), respectively.

Increasing TILs were associated with increasing five-year mortality and risk of COPD-related hospitalization. TILs may be used as a proxy for underlying COPD severity in epidemiological studies.