Table 2 Baseline demographic and clinic data and risk factors for AAD

· Age

years

· Sex

male; female

· Race

white; black; Asian; Chinese; other

· Period of recruitment

summer (May – Sept); winter (Oct-March)

· Smoking

usual number of cigarettes/day

· Alcohol

usual number of units/week

· Where admitted from

home; residential care; other hospital; other

· Admission type

emergency/unplanned; elective/ planned for procedure or investigation

· Admission diagnosis or main cause of admission

· Co-morbidity

hypertension; asthma; diabetes; chronic obstructive airways disease; renal disease; irritable bowel syndrome; dementia; Alzheimer’s disease; other

· Previous GI surgery

· Number of hospital admissions in last eight weeks

· Antacid treatment

antacid; H₂-receptor antagonist; proton pump inhibitor

· Naso-gastric tube in-situ

· Duration of hospital stay prior to recruitment

days

· Indication for antibiotic treatment

· Antibiotic treatment: antibiotic used¹

single class; 2 classes; 3 or more classes

· Antibiotic treatment: total duration

single dose; 1–6 days; 7–13  days; ≥14 days