The purpose of this thesis was to examine the association between comorbid heart failure (HF) and acute exacerbations of chronic obstructive pulmonary disease (AECOPD) in primary care COPD patients to highlight areas in which care can be improved.

The aims of this research were:
i. To describe the burden of HF comorbidity in the COPD population;
ii. To determine the effect of HF comorbidity on exacerbation risk in COPD patients; and
iii. To determine the effect of HF medications on exacerbation risk in COPD patients with HF.

Firstly, a systematic review revealed that HF comorbidity increases COPD-related secondary care utilisation and all-cause mortality of COPD patients; however, the heterogeneity prevented meta-analysis to estimate pooled effects using all available data. Secondly, analysis found that HF incidence was steady from 2006 to 2016 in the COPD population. COPD patients with HF experienced higher short- and long-term mortality rates than those without HF. Thirdly, HF diagnosis was associated with a significantly greater risk for AECOPD compared to patients without evidence of HF. In a population identified as having possible HF, AECOPD risk was also elevated. Only 50% of possible HF patients had documented HF investigation. Finally, incident use of HF medications was associated with increased AECOPD risk compared to non-use of HF medications in COPD patients with diagnosed HF; however, AECOPD risk decreased relative to incident medication use beyond six months of treatment.

These results demonstrate that HF comorbidity has a considerable effect on AECOPD in the primary care COPD population and that management of HF pharmacologically may reduce excess AECOPD risk. Additionally, there appear to be substantial opportunities for earlier recognition of HF in the COPD population in the primary care setting. Proactive targeting of HF in the COPD population by primary care providers may help to improve patient outcomes.