Table 2 Hazard ratios of determinants of developing a next exacerbation after oral corticosteroids with antibiotics—compared with oral corticosteroids only—treatment in a multivariable Cox model

	HR of new exacerbation	99% CI for hazard ratio
	HR of new exacerbation	Lower	Upper
Antibiotics added to treatment with oral corticosteroids
0–3 months following treatment	0.62	0.60	0.65
3–6 months following treatment	0.68	0.65	0.73
6–12 months following treatment	1.03	0.96	1.12
>12 months following treatment	1.31	1.18	1.45
Exposure to antibiotics after previous exacerbation	0.82	0.78	0.87
Female sex	0.95	0.91	1.00
Inhaled corticosteroids as maintenance medication	0.91	0.84	0.98
Co-medication cardiovascular	1.16	1.10	1.23
Co-medication for diabetes	1.05	0.98	1.12
Hospitalisation* for COPD†	1.45	1.35	1.57
Hospitalisation for pneumonia	1.19	1.05	1.34

The variables “age” and “number of respiratory drugs dispensings in 2003” were included in the Cox model, but were not fitted linearly, and therefore HR are not presented.
*Once or more in previous 2 years. †Diagnosis: chronic bronchitis, emphysema or COPD.
COPD, chronic obstructive pulmonary disease; HR, hazard ratio.