Anemia is Associated with Bone Mineral Density in Chronic Obstructive Pulmonary Disease

Figures & data

Figure 1.  Bone mineral density by plasma haemoglobin concentration.

Table 1.  General characteristics of the total study group and after stratification for anemia

	Total group	Anemia	Normal Hb	Polycythemia	Significances
Number, n(%)	321	63(19)	232(72)	27(8)
Gender, n(%) male	180(56)	52(83)a,b	120(53)b	4(15)	p < 0.01
Age, y	64 ± 9	65 ± 9	64 ± 9	66 ± 8
PYa	46.4 ± 50.3	47.6 ± 22.5	47.6 ± 56.9	31.0 ± 14.7
Lung function parameters and arterial blood gases
FEV1, L	1.23 ± 0.55	1.33 ± 0.54	1.22 ± 0.57	1.06 ± 0.44
FEV1,%pred	46.2 ± 18.7	46.3 ± 17.2	46.0 ± 19.0	47.1 ± 15.3
FEV1/FVC	37.9 ± 12.2	37.0 ± 12.2	38.1 ± 12.3	38.9 ± 11.1
DLCO,%pred	50.2 ± 18.1	48.9 ± 15.7	50.4 ± 18.9	51.7 ± 17.1
LTOT, n(%)	92(33)	12(24)	68(34)	14(50)
PaO2, mmHg	9.4 ± 1.7	9.6 ± 1.7	9.3 ± 1.6	10.0 ± 2.4
PaCO2, mmHg	4.6 ± 0.7	4.5 ± 0.7	4.6 ± 0.8	4.5 ± 0.6
Body composition parameters and T–scores
BMI, kg/m2	25.5 ± 5.8	25.3 ± 5.2	25.4 ± 6.0	27.4 ± 5.3
FFMI, kg/m2	16.6 ± 2.5	17.2 ± 2.1	16.4 ± 2.6	16.3 ± 2.2
BMD, g/cm2	1.08 ± 0.11	1.04 ± 0.11a,b	1.08 ± 0.11b	1.14 ± 0.09	p < 0.01
T–score hip	–1.65 ± 1.05	–1.72 ± 1.02	–1.63 ± 1.07	–1.74 ± 0.90
T–score lumbal spine	–1.19 ± 1.50	–1.39 ± 1.48	–1.13 ± 1.54	–1.22 ± 1.16
Lowest T–score	–1.92 ± 1.08	–2.06 ± 1.04	–1.88 ± 1.11	–1.91 ± 0.90
Functional outcomes
mMRC dyspnea grade	3.5 ± 1.0	3.4 ± 1.0	3.5 ± 1.0	3.6 ± 1.0
BODE score, points	4.7 ± 2.0	4.6 ± 1.9	4.8 ± 2.0	4.5 ± 1.7
SGRQ
Symptoms	58.9 ± 19.9	61.3 ± 19.3	58.5 ± 19.6	56.7 ± 22.7
Activity	78.7 ± 17.6	80.4 ± 16.2	78.1 ± 17.7	80.0 ± 20.1
Impact	45.6 ± 18.6	46.6 ± 17.4	44.9 ± 18.2	48.6 ± 23.3
Total	57.8 ± 16.0	59.3 ± 14.4	57.3 ± 16.0	59.4 ± 19.5
6MWD, m	414.8 ± 117.4	435.8 ± 106.1	410.0 ± 122.7	407.3 ± 90.6
Saturation drop during 6MWD,%	–5.6 ± 5.2	–5.2 ± 5.4	–5.8 ± 5.3	–5.4 ± 4.3
Self–reported co–morbidities, n(%)
Cardiovascular disease	20(6)	4(6)	15(6)	1(4)
Chronic heart failure	14(4)	6(10)	7(3)	1(4)
Diabetes Mellitus type II	37(11)	7(11)	25(11)	5(19)
Hypercholesterolemia	15(5)	3(5)	9(4)	3(11)
Hypertension	65(20)	8(13)	51(22)	6(22)
Anemia	9(3)	2(3)	7(3)	0
Biochemical markers
Creatinin, mg/dl	1.6 ± 0.4	1.7 ± 0.4b	1.6 ± 0.4	1.5 ± 0.4	p = 0.03
eGFR, ml/min	72.9 ± 19.4	73.9 ± 19.3	72.8 ± 19.6	71.4 ± 17.6
CRP, mg/l	3.9 (1.3–10.6)	6.6 (2.3–17.5)a,b	3.4 (1.2–10.6)	2.5 (0.9–5.3)	p = 0.01
Hb, g/dl	13.8 ± 1.4	12.0 ± 0.8a,b	14.1 ± 0.9b	16.1 ± 1.2	p < 0.01
MCV, fL	94.2 ± 7.0	92.7 ± 10.8	94.7 ± 5.9	93.4 ± 3.6


#Data available of only 214 subjects. Symbols: ap < 0.05 vs. normal Hb, bp < 0.05 vs. polycythemia. Abbreviations: PY: number of pack-years, FEV1: forced expiratory volume in 1 second, FVC: functional vital capacity, FEV1/FVC: Tiffeneau index, DLCO: diffusion capacity of carbon monoxide, PaO2: arterial oxygen pressure, PaCO2: arterial carbon-dioxide pressure, LTOT: long-term oxygen pressure, BMI: body mass index, FFMI: fat free mass index, BMD, total body bone mineral density, mMRC: modified Medical Research Council dyspnoea scale, BODE: body mass index, airflow obstruction, dyspnea, exercise capacity, 6MWD: 6-minute walking distance, SGRQ: St.-George Respiratory Questionnaire (SGRQ), Hb: plasma haemoglobin concentration score, MCV: mean corpuscular volume.

Table 2.  Prevalence of objectively diagnosed co-morbidities and risk for undernutrition

	Total group	Anemia	Normal Hb	Polycythemia	Significances
Low muscle mass	110(35)	16(25)	90(40)	4(15)	p < 0.01
Osteoporosis	101(31)	22(35)	69(30)	10(37)
Osteopenia	162(50)	31(49)	118(51)	13(48)
Renal failure (all overt)	78(24)	18(29)	54(23)	6(22)
SNAQ risk (score ≥2)	46(15)	8(13)	36(16)	2(8)

SNAQ: Short Nutritional Assessment questionnaire, Hb: plasma haemoglobin concentration.

Table 3.  Association of anemia or polycythemia with mMRC, CRP and bone mineral density after adjustment for confounders

	mMRC		CRP		Bone mineral density
	Beta	p-value	Beta	p-value	Beta	p-value
Age	0.01	0.86	–0.10	0.06	0.01	0.56
FEV1	–0.72	<0.01	–0.04	0.60	–0.01	0.81
BMI	0.04	<0.01	0.01	0.15	0.01	0.58
PaO2	0.01	0.95	–0.02	0.50	0.01	0.96
Plasma Hb
Anemia	–0.05	0.71	0.22	0.04	–0.04	0.01
Normal Hb	Ref		Ref		Ref
Polycythemia	–0.19	0.36	-0.26	0.12	0.05	0.07

FEV1: forced expiratory volume in 1 second, BMI: body mass index, PaO2: arterial oxygen pressure, Hb: haemoglobin, mMRC: modified Medical Research Council, CRP: C-reactive protein.

Table 4.  Association of anemia or polycythemia with low muscle mass after adjusted for confounders

	OR	95%CI	p-value
Age	1.00	0.96–1.03	0.88
BMI	0.66	0.59–0.73	<0.01
Plasma Hb			0.08
Anemia	0.45	0.21–0.99	0.05
Normal Hb	Ref
Polycythemia	0.43	0.12–1.48	0.18

BMI: body mass index, Hb: plasma haemoglobin concentration.