Table 2

Crude counts and rates of outcome variables (testing for the presence of a Hawthorne effect)

VariableCategoryCPRD-GMCPRD-xGMSLS COPD
n204916 7581403
Count of AECOPD episodes*Number of events269320 1842288
Rate per person-year (95% CI)1.63 (1.57 to 1.69)1.53 (1.51 to 1.56)1.91 (1.83 to 1.99)
Count of strict definition of AECOPD†episodesNumber of events5833497766
Rate per person-year (95% CI)0.32 (0.30 to 0.35)0.24 (0.24 to 0.25)0.58 (0.54 to 0.62)
MortalityNumber of cases144114524
Rate per 1 000 person-years (95% CI)78.19 (65.94 to 92.06)78.49 (74.01 to 83.17)17.51 (11.22 to 26.05)
Number of days contact with primary careCount48 167399 29166 308
Rate per person-year (95% CI)26.19 (25.96 to 26.43)27.37 (27.29 to 27.46)49.11 (48.74 to 49.49)
Countof COPD-related prescription items‡Count25 433187 39632 133
Rate per person-year (95% CI)13.81 (13.64 to 13.98)12.85 (12.79 to 12.90)23.44 (23.18 to 23.70)
Treatment switching§% switch at some point in follow-up36.1640.7734.67
  • For full definitions of above outcomes, see online supplementary appendix 1.

  • *AECOPD events were those that met any criteria from the validated algorithm.16

  • †The strict definition of AECOPD events was strictly medical codes for acute exacerbation of COPD.

  • ‡Prescription of any treatment counted as usual care in SLS COPD.

  • §Switching from one treatment class to another during follow-up.

  • AECOPD, acute exacerbations of COPD; COPD, chronic obstructive pulmonary disease; CPRD-GM, Clinical Practice Research Datalink in Greater Manchester; CPRD-xGM, Clinical Practice Research Datalink outside of Greater Manchester; SLS COPD, Salford Lung Study in chronic obstructive pulmonary disease.