Table 5– Adjusted association between hospitalisation rate and annual change in 6-min walk distance (6MWD) during 1.7-year follow-up in 342 chronic obstructive pulmonary disease (COPD) patients^# in all patients and according to cause of admission

	All patients		*Patients with only-COPD admissions^¶ versus* no admissions⁺**		*Patients with nonrespiratory admissions^§ versus* no admissions⁺**
	Coefficient^ƒ (95% CI)	p-value	Coefficient^ƒ (95% CI)	p-value	Coefficient^ƒ (95% CI)	p-value
Constant^##	−7.3 (−15.8–1.2)	0.088	−7.7 (−15.8–0.6)	0.068	−8.5 (−16.7– −0.3)	0.043
Number of hospital admissions per year during follow-up
0	Reference		Reference		Reference
>0 and ≤1	−7.4 (−19.1–4.3)	0.211	−13.8 (−28.2–2.1)	0.092	−1.5 (−18.7–15.7)	0.865
>1	−26.1 (−38.6– −13.1)	<0.001	−28.0 (−45.1– −10.7)	0.002	−27.3 (−48.9– −5.6)	0.014
Significant dyspnoea^¶¶ at baseline	−17.2 (−27.8– −6.6)	0.002	−16.9 (−28.3– −5.4)	0.004	−15.3 (−26.4– −4.1)	0.008
Age at baseline years	−0.6 (−1.3–0.01)	0.057	−0.6 (−1.2–0.1)	0.089	−0.6 (−1.3–0.1)	0.098
Female sex	−11.1 (−30.2–7.9)	0.249	−8.6 (−29.1–11.9)	0.407	−4.3 (−24.9–16.3)	0.679
Baseline body mass index kg·m⁻²	−0.3 (−1.5–0.9)	0.664	−0.2 (−1.4–1.1)	0.782	−0.6 (−1.8–0.7)	0.389
Baseline RV/TLC %	−0.5 (−1.0–0.04)	0.069	−0.5 (−1.2–0.1)	0.087	−0.4 (−0.9–0.2)	0.223
Baseline P_aO₂ mmHg	0.1 (−0.2–0.4)	0.692	0.1 (−0.3–0.4)	0.726	0.1 (−0.2–0.5)	0.398
Baseline 6MWD m	−0.2 (−0.3– −0.1)	<0.001	−0.2 (−0.3– −0.1)	<0.001	−0.2 (−0.3– −0.1)	<0.001
Adjusted R²	0.223		0.229		0.193

RV: residual volume; TLC: total lung capacity; P_aO₂: arterial oxygen tension. ^#: linear regression model. ^¶: n=77. ⁺: n=189. ^§: n=43.^ƒ: expressed as change in metres of 6MWD per: 1) unit of the continuous covariate, or 2) a change with respect to the reference category in categorical covariates. ^##: adjusted mean value based on the linear regression equation corresponding to the mean change in 6MWD in a subject with no COPD hospitalisations per year and modified Medical Research Council score <2, who was male and of mean age, body mass index, RV/TLC, P_aO₂ and baseline 6MWD; negative values represent decline. ^¶¶: modified Medical Research Council score ≥2.