Table 1. Summary of Confounding Variables, by Category, Measured Prior to Index Prescription and by which Propensity Scores were Adjusted.

Demographics	Respiratory disease severity (past year)	General health	Co-medications associated previously with CAP (past year)
Age	Asthma	Healthcare use (in past year)	Statins [34]
		- Number of emergency hospitalizations
		- Number of non-emergency hospitalizations
		- Number of general practice visits
Gender	COPD severity	Charlson comorbidity chapters as defined by Khan et al [36] minus HIV (too infrequent) and respiratory disease (ever)	ACE-inhibitors [35]
	- Lung function less than FEV1 % predicted
	- Moderate to severe dyspnea (Medical Research Council >2)
	- Number of moderate and severe COPD exacerbations
Calendar year of index prescription	Respiratory medications	Additional comorbidities associated	Immunosuppressants [37]
	- Short-acting beta-agonists	with pneumonia (ever)
	- Oral corticosteroids	- Depression
	- Theophyllines	- Anxiety
	- Oxygen use	- GERD
	- Nebulized therapies
Smoking status		Pneumonia (past year)	GERD medications
Body mass index		Vaccinations	Benzodiazepines and non-
		- Influenza (past year)	benzodiazepine sedatives [38]
		- Pneumococcal (past 5 years)
Socio-economic status
- Overall Social Deprivation Scores for England [39]
- Townsend Score
- Pneumonia in the baseline period (CAP and severe CAP)

ACE: angiotensin-converting-enzyme; CAP: community-acquired pneumonia; FEV₁: forced expiratory volume in 1s; GERD: gastroesophageal reflux disease.