Predictors of mortality in patients with COPD after 9 years

Figures & data

Table 1 Demographic and clinical characteristics of the patients included in the analysis of predictors of mortality according to FEV₁ (GOLD classification of FEV₁ severity) of COPD at baseline

Variable	Total (N=110)	COPD GOLD 1 and 2 n=53	COPD GOLD 3 and 4 n=57	P-value
Male/female sex, n	74/36	33/20	41/16	0.381^a
Age, years	65 (59–72)	65 (59–73)	67 (61.5–73)	0.536^b
SB, pack-years	50 (35–67)	50 (40–71.5)	50 (30–59)	0.173^b
SpO2, %	94 (92–96)	94 (93–97)	93 (91–95)	0.003^b
FEV1, % of the predicted	52.5 (40–73)	73 (60–87.5)	40 (32.5–46.5)	<0.001^b
FEV1, L	1.20 (0.93–1.72)	1.65 (1.32–2.14)	0.94 (0.75–1.09)	<0.001^b
BMI, kg/m^2	25 (21–28)	25.8 (21.7–31.1)	24.4 (20.7–27.4)	0.097^b
Fat-free mass, kg	42 (7)	41.5 (7.4)	41.9 (7.1)	0.787^c
mMRC, score	1 (1–2)	1 (1–2)	2 (1–3)	0.006^b
6MWT, m	430 (91)	457 (85)	404 (89)	0.002^c
BODE, class	1 (1–2)	1 (1–1)	2 (1–3)	<0.001^b

Notes: Parametric data are expressed as mean and SD and nonparametric data as median (IQR 25–75). The 2004 GOLD classification of airflow limitation severity – GOLD 1 or GOLD 2 vs GOLD 3 or GOLD 4 (^achi-squared test, ^bMann–Whitney, or ^cunpaired t-test). BODE index: class 1 (score 0–2), class 2 (score 3 and 4), class 3 (score 5 and 6), and class 4 (score 7–10).

Abbreviations: 6MWT, 6-minute walk test; BMI, body mass index; BODE, Body mass index, airway Obstruction, Dyspnea, and Exercise capacity; SB, smoking burden; SpO₂, pulse oximetry; mMRC, Modified Medical Research Council.

Figure 1 Flowchart of all patients included in the study.

Figure 2 Medication classes used at baseline according to the GOLD classification.

Abbreviations: LABA, long-acting beta 2 agonists; LTOT, long-term oxygen therapy; SABA, short-acting beta 2 agonists.

Figure 3 Causes of death according to severity of COPD.

Table 2 Comparison between the baseline characteristics according to survival status (survivors vs non-survivors) after 9 years

Variable	Total (N=110)	Survivors (n=46)	Non-survivors (n=64)	P-value
Male/female sex, n	75/35	28/18	47/17	0.235a
Age, years	65 (9.4)	61.5 (8.7)	67.6 (9)	<0.001b
SB, pack-years	50 (34.7–70)	43 (30–75)	50 (40–69)	0.616c
SpO2, %	93 (92–96)	94 (92.7–96)	93 (91–95)	0.035c
FEV1, % of the predicted	52.5 (39–73.2)	61 (46.5–79)	46 (37–64.7)	0.004c
FEV1, L	1.21 (0.94–1.71)	1.47 (0.99–1.92)	1.10 (0.86–1.48)	0.020c
BMI, kg/m^2	25 (21–28)	25.4 (22.3–28.6)	24.5 (20.6–28)	0.142c
Fat-free mass, kg	41.6 (7.3–0.7)	41 (7)	42 (7.5)	0.556b
mMRC, score	1 (1–2)	1 (1–2)	2 (1–2)	0.076c
6MWT, m	429 (94.2)	461 (90.4)	406 (90.6)	0.002b
BODE, class	1 (1–2)	1 (1–1.2)	2 (1–3)	<0.001c

Notes: Parametric data are expressed as mean and SD and nonparametric as median (IQR 25–75).

a Chi-squared test,

b unpaired t-test, or

c Mann–Whitney. BODE index: class 1 (score 0–2), class 2 (score 3 and 4), class 3 (score 5 and 6), and class 4 (score 7–10).

Abbreviations: 6MWT, 6-minute walk test; BMI, body mass index; BODE, Body mass index, airway Obstruction, Dyspnea, and Exercise capacity; SB, smoking burden; SpO₂, pulse oximetry; mMRC, Modified Medical Research Council.

Figure 4 Kaplan–Meier survival curves of all patients according to BODE index classification (A) body mass index (B) and 2004 GOLD severity classification (C).

Abbreviation: BODE, Body mass index, airway Obstruction, Dyspnea, and Exercise capacity.

Table 3 Cox regression analysis to identify the predictors of mortality in the 9-year period

Variables	HR (95% CI), N=110	P-value
Male	1.34 (0.68–2.63)	0.390
Age (years)	0.98 (0.93–1.03)	0.610
SpO2 (%)	0.94 (0.85–1.04)	0.258
BODE index class 1 – reference	*	*
BODE index class 2	2.62 (1.36–5.04)	0.004
BODE index class 3	2.54 (1.15–5.61)	0.021
BODE index class 4	15.35 (3.11–75.75)	0.001
Charlson Comorbidity Index	1.29 (1.00–1.68)	0.049
Exacerbation (n)	1.32 (1.00–1.76)	0.048

Notes: All variables were included together in the Cox proportional hazard regression analysis (sex, age, SpO₂, BODE index, CCI, and number of exacerbations in the first 3 years). BODE exacerbation, number of exacerbations in the 3-year period of follow-up; index, class 1 (score 0–2), class 2 (score 3 and 4), class 3 (score 5 and 6), and class 4 (score 7–10).

Abbreviations: BODE, Body mass index, airway Obstruction, Dyspnea, and Exercise capacity; SpO₂, pulse oximetry.

Table 4 Cox regression analysis with replacement of the BODE index for the variables that compose it

Variables	HR (95% CI), N=110	P-value
Male	1.36 (0.66–2.76)	0.396
Age (years)	0.97 (0.93–1.03)	0.434
SpO2 (%)	0.93 (0.84–1.03)	0.170
6MWT (m)	0.99 (0.99–1.00)	0.305
FEV1 (%)	0.99 (0.97–1.00)	0.417
BMI >21 kg/m^2 (reference)	*	*
BMI (≤21 kg/m^2)	2.70 (1.38–5.25)	0.003
mMRC (score)	1.06 (0.75–1.50)	0.730
CCI	1.29 (0.99–1.68)	0.057
Exacerbation (n)	1.38 (1.03–1.85)	0.027

Notes: All variables were included together in the Cox proportional hazard regression (sex, age, SpO₂, 6MWT, BMI, mMRC, CCI, and number of exacerbations in first 3 years). Exacerbation, number of exacerbations per patient in the 3-year period.

Abbreviations: 6MWT, 6-minute walk test; BMI, body mass index; BODE, Body mass index, airway Obstruction, Dyspnea, and Exercise capacity; CCI, Charlson Comorbidity Index; SpO₂, pulse oximetry; mMRC, Modified Medical Research Council.

Table S1 Cox regression analysis with GOLD severity classification to identify the predictors of mortality in the 9-year period

Variables	HR (95% CI) N=110	P-value
Male	1.25 (0.64–2.55)	0.536
Age (years)	0.98 (0.92–1.03)	0.465
SpO2 (%)	0.96 (0.85–1.08)	0.521
6MWT (m)	0.99 (0.99–1.00)	0.625
BMI >21 kg/m^2	0.96 (0.91–1.02)	0.304
GOLD 1 – reference
GOLD 2	1.16 (0.37–3.61)	0.798
GOLD 3	1.63 (0.53–4.99)	0.390
GOLD 4	2.18 (0.63–7.60)	0.218
mMRC (score)	1.13 (0.80–1.59)	0.481
CCI	1.32 (0.99–1.76)	0.058
Exacerbation (n)	1.24 (0.92–1.69)	0.153

Notes: All variables were included together in the Cox proportional hazard regression (sex, age, SpO₂, 6MWT, BMI, mMRC, CCI, number of exacerbations in first 3 years, and 2004 GOLD classification of airflow limitation severity). Exacerbation, number of exacerbations per patient in the 3-year period.

Abbreviations: 6MWT, 6-minute walk test; BMI, body mass index; CCI, Charlson Comorbidity Index; SpO₂, pulse oximetry; mMRC, Modified Medical Research Council.

Table S2 Cox regression analysis with replacement of the BODE index for the variables that compose it, without patients with neoplasm, to identify the predictors of mortality in the 9-year period

Variables	HR (95% CI) N=110	P-value
Male	0.29 (0.64–2.78)	0.428
Age (years)	−0.20 (0.93–1.03)	0.464
SpO2 (%)	−0.04 (0.85–1.07)	0.430
6MWT (m)	−0.002 (0.73–1.50)	0.243
FEV1 (%)	−0.004 (0.98–1.01)	0.583
BMI <21 kg/m^2	1.00 (1.38–5.33)	0.004
mMRC (score)	0.48 (0.73–1.50)	0.794
CCI	0.24 (0.97–1.68)	0.074
Exacerbation (n)	0.38 (1.08–1.99)	0.013

Notes: All variables were included together in the Cox proportional hazard regression (sex, age, SpO₂, 6MWT, BMI, mMRC, CCI, and number of exacerbations in first 3 years) without patients with neoplasm during the follow-up. Exacerbation, number of exacerbations per patient in the 3-year period.

Abbreviations: 6MWT, 6-minute walk test; BMI, body mass index; BODE, Body mass index, airway Obstruction, Dyspnea, and Exercise capacity; CCI, Charlson Comorbidity Index; SpO₂, pulse oximetry; mMRC, Modified Medical Research Council.