Hemoglobin and mortality in patients with COPD: a nationwide population-based cohort study

Figures & data

Figure 1 Flow chart of the study population.

Abbreviations: ICD-10, International Classification of Disease-Tenth Revision; NHIS-Heals, National Health Insurance Service-Health Screening.

Table 1 Demographic and clinical characteristics of COPD patients with or without anemia

Variable	Anemia (n=469)	Non-anemia (n=6,645)	p-value
Male	291 (62.1)	4,185 (63.0)	0.686
Age (years)	67.8±8.6	64.8±9.3	<0.001
40–49	21 (4.5)	552 (8.3)
50–59	51 (10.9)	1,154 (17.4)
60–69	172 (36.7)	2,666 (40.1)
≥70	225 (48.0)	2,273 (34.2)
Hemoglobin (mg/dL)	11.5±1.1	14.2±1.2	<0.001
Household income			0.064
<20%	120 (25.6)	1,328 (20.0)
20%–39%	78 (16.6)	1,133 (17.1)
40%–59%	69 (14.7)	1,040 (15.7)
60%–79%	90 (19.2)	1,351 (20.3)
≥80%	112 (23.9)	1,793 (27.0)
CCI			<0.001
1	112 (23.9)	2,437 (36.7)
2	171 (36.5)	2,501 (37.6)
3	128 (27.3)	1,192 (17.9)
≥4	58 (12.4)	515 (7.8)
BMI (kg/m^2)			<0.001
<18.5	88 (18.9)	182 (6.9)
18.5–22.9	203 (43.5)	994 (37.7)
23.0–24.9	80 (17.1)	648 (24.6)
25.0–29.9	87 (18.6)	734 (27.8)
≥30.0	9 (1.9)	81 (3.1)
Smoking			0.109
Never	303 (67.5)	1,584 (62.9)
Ex	45 (10.0)	328 (13.0)
Current	101 (22.5)	608 (24.1)
Deaths	218 (46.5)	2,132 (32.1)	<0.001

Note: Data are shown as the mean ± SD or number (%).

Abbreviations: BMI, body mass index; CCI, Charlson comorbidity index.

Table 2 Cox proportional hazards model for factors associated with mortality in COPD patients

Variable	Univariate		Multivariate (anemia)		Multivariate (hemoglobin)
	HR (95% CI)	p-value	HR (95% CI)	p-value	HR (95% CI)	p-value
Anemia	1.69 (1.47–1.95)	<0.001	1.31 (1.11–1.54)	0.002	–	–
Hemoglobin (mg/dL)
≥13.0	1		–	–	1
11.0–12.9	1.17 (1.02–1.36)	0.031	–	–	1.23 (1.04–1.45)	0.017
9.0–10.9	1.57 (1.10–2.25)	0.014	–	–	1.62 (1.10–2.39)	0.014
7.0–8.9	3.48 (1.97–6.16)	<0.001	–	–	2.74 (1.53–4.88)	0.001
<7.0	5.09 (1.27–20.35)	0.022	–	–	5.12 (1.25–20.97)	0.023
Female	0.44 (0.40–0.48)	<0.001	0.48 (0.41–0.57)	<0.001	0.44 (0.36–0.53)	<0.001
Age (years)
40–49	1		1		1
50–59	2.74 (1.77–4.23)	<0.001	3.18 (1.57–6.42)	0.001	3.19 (1.58–6.45)	0.001
60–69	7.97 (5.31–11.95)	<0.001	7.89 (4.07–15.32)	<0.001	7.88 (4.05–15.30)	<0.001
≥70	19.25 (12.87–28.81)	<0.001	18.77 (9.70–36.33)	<0.001	18.86 (9.77–36.52)	<0.001
Household income
<20%	1		1		1
20%–39%	0.90 (0.79–1.02)	0.115	0.90 (0.74–1.10)	0.322	0.90 (0.74–1.10)	0.310
40%–59%	0.79 (0.69–0.91)	0.001	0.77 (0.62–0.96)	0.019	0.76 (0.61–0.95)	0.016
60%–79%	0.80 (0.71–0.91)	0.001	0.79 (0.65–0.96)	0.020	0.79 (0.65–0.97)	0.022
≥80%	0.84 (0.75–0.94)	0.003	0.82 (0.68–0.99)	0.035	0.82 (0.68–0.98)	0.032
CCI
1	1		1		1
2	1.07 (0.97–1.18)	0.181	1.09 (0.97–1.28)	0.261	1.09 (0.93–1.27)	0.274
3	1.37 (1.22–1.53)	<0.001	1.22 (1.01–1.47)	0.042	1.20 (1.00–1.45)	0.057
≥4	2.04 (1.78–2.35)	<0.001	1.33 (1.03–1.71)	0.027	1.34 (1.04–1.72)	0.023
BMI (kg/m^2)
<18.5	1		1		1
18.5–22.9	0.45 (0.38–0.53)	<0.001	0.54 (0.45–0.57)	<0.001	0.54 (0.45–0.65)	<0.001
23.0–24.9	0.28 (0.23–0.34)	<0.001	0.42 (0.34–0.53)	<0.001	0.43 (0.34–0.53)	<0.001
25.0–29.9	0.21 (0.17–0.26)	<0.001	0.34 (0.27–0.43)	<0.001	0.35 (0.28–0.44)	<0.001
≥30.0	0.12 (0.07–0.23)	<0.001	0.27 (0.15–0.51)	<0.001	0.27 (0.15–0.50)	<0.001
Smoking
Never	1		1		1
Ex	1.47 (1.22–1.78)	<0.001	1.07 (0.88–1.30)	0.500	1.08 (0.89–1.31)	0.466
Current	1.40 (1.20–1.62)	<0.001	1.03 (0.88–1.21)	0.676	1.03 (0.88–1.21)	0.684

Abbreviations: BMI, body mass index; CCI, Charlson comorbidity index; HR, hazard ratio.

Figure 2 Kaplan–Meier survival curves for anemia and non-anemia.

Figure 3 Kaplan–Meier survival curves by different hemoglobin levels.