Table 2

Crude and clinical model adjusted individual associations between relevant variables* and readmission to hospital for an exacerbation in a cohort of 312 patients with COPD (Cox regression)

Crude HR
(95% CI)†		p valueAdjusted HR
(95% CI) by clinical model†		p value
HR=hazard ratio; CI=confidence interval; MDI=metered dose inhaler; QoL=quality of life.
*Relevant variables are: those considered a priori as clinically relevant, those with a p value <0.250 after adjusting for the clinical model, and those with high (>2) or low (<0.5) HR after adjusting for the clinical model.
†Each line is a single model. Clinical model includes: ⩾3 COPD admissions in the year before recruitment, ⩾3 COPD emergency room visits without admission in the year before recruitment, % predicted FEV1, and Po2.
‡Reference categories are: <3 COPD admissions in the year before recruitment; <3 COPD emergency room visits without admission in the year before recruitment; not team based primary care; no anticholinergics intake; no oral corticosteroids intake; lack of influenza vaccination; lack of respiratory rehabilitation; lack of long term oxygen therapy; some mistake in any of the essential MDI manoeuvres.
§HR means change in risk for 1 percentual unit in FEV1, 1 kPa in Po2, and 1 point increase in physical scale of SF-36 score.
¶First tertile means, for instance, patients walking 20 minutes a day every day (“walking” includes time going to the bar, to buy newspapers, going to the supermarket, or just strolling). Third tertile means patients walking 60 minutes a day every day, or patients walking 20 minutes a day plus practising exercise in a gymnasium 60 minutes a day three days a week.
Clinical model
    ⩾3 COPD admissions in the year before recruitment‡2.27 (1.69 to 3.04)0.000
    ⩾3 COPD emergency room visits without admission in the year before recruitment‡1.72 (1.13 to 2.61)0.012
    % predicted FEV1§0.97 (0.96 to 0.98)0.000
    po2 (kPa)§0.78 (0.71 to 0.87)0.000
Age1.00 (0.99 to 1.02)0.7031.01 (0.99 to 1.04)0.163
Sex: women0.98 (0.60 to 1.61)0.9341.43 (0.76 to 2.68)0.265
Medical care
    Team based primary care‡0.74 (0.57 to 0.97)0.0290.77 (0.56 to 1.07)0.116
    Controlled by a:
        General practitioner1.001.00
        Pulmonologist2.16 (1.43 to 3.27)0.0001.77 (1.07 to 2.92)0.025
    Hospital of recruitment:
        Hospital 11.001.00
        Hospital 21.88 (1.28 to 2.75)0.0011.81 (1.14 to 2.88)0.012
        Hospital 31.95 (1.32 to 2.88)0.0012.08 (1.33 to 3.27)0.001
        Hospital 41.07 (0.69 to 1.65)0.7611.19 (0.67 to 2.14)0.550
Medical prescriptions
    Anticholinergics‡3.52 (2.37 to 5.21)0.0002.02 (1.26 to 3.24)0.004
    Oral corticosteroids‡1.55 (1.13 to 2.11)0.0061.59 (1.07 to 2.37)0.021
    Influenza vaccination‡1.37 (1.01 to 1.87)0.0441.43 (0.98 to 2.07)0.064
    Respiratory rehabilitation‡1.77 (1.23 to 2.57)0.0021.32 (0.85 to 2.05)0.223
    Long term oxygen therapy‡2.36 (1.79 to 3.11)0.0001.26 (0.87 to 1.84)0.224
Compliance
    Correctly performed essential MDI manoeuvres‡1.17 (0.88 to 1.56)0.2771.12 (0.79 to 1.59)0.526
Lifestyle
    Smoking:
        Ex smoker not exposed to passive smoking1.001.00
        Ex smoker exposed to passive smoking1.18 (0.81 to 1.70)0.3871.63 (1.04 to 2.57)0.034
        Current smoker0.58 (0.41 to 0.82)0.0020.97 (0.64 to 1.47)0.876
        Never smoker0.93 (0.55 to 1.57)0.7811.20 (0.61 to 2.33)0.598
    Usual physical activity (in tertiles)¶
        <79 kcal/day1.001.00
        79–232 kcal/day0.73 (0.54 to 0.99)0.0430.85 (0.59 to 1.24)0.400
        >232 kcal/day0.46 (0.32 to 0.68)0.0000.49 (0.31 to 0.79)0.003
Other
    Physical scale health related QoL§0.97 (0.95 to 0.98)0.0000.98 (0.96 to 0.99)0.007