Objective
Little is known about how lower respiratory tract infections (LRTIs) before chronic obstructive pulmonary disease (COPD) are associated with future exacerbations and mortality. We investigated this association in COPD patients in England.
Methods
Clinical Practice Research Datalink Aurum, Hospital Episode Statistics, and Office of National Statistics data were used. Start of follow-up was patient’s first ever COPD diagnosis date and a 1-year baseline period prior to start of follow-up was used to find mild LRTIs (GP events/no antibiotics), moderate LRTIs (GP events +antibiotics), and severe LRTIs (hospitalised). Patients were categorised as having: none, 1 mild only, 2+ mild only, 1 moderate, 2+ moderate, and 1+ severe. Negative binomial regression modelled the association between baseline LRTIs and subsequent COPD exacerbations and Cox regression was used to investigate mortality.
Results
In 215,234 COPD patients, increasing frequency and severity of mild and moderate LRTIs were associated with increased rates of subsequent exacerbations compared to no recorded LRTIs (1 mild adjusted IRR 1.16, 95%CI 1.14-1.18, 2+ mild IRR 1.51, 95%CI 1.46-1.55, 1 moderate IRR 1.81, 95%CI 1.78-1.85, 2+ moderate IRR 2.55, 95%CI 2.48-2.63). Patients with 1+ severe LRTI (vs. no baseline LRTIs) also showed an increased rate of future exacerbations (adjusted IRR 1.75, 95%CI, 1.70-1.80). This pattern of association was similar for risk of all-cause and COPD-related mortality however, patients with 1+ severe LRTIs had the highest risk of all-cause and COPD mortality.
Conclusion
Increasing frequency and severity of LRTIs prior to COPD diagnosis were associated with increasing rates of subsequent exacerbations, and increasing risk all-cause and COPD-related mortality.