Is iron deficiency modulating physical activity in COPD?

Figures & data

Table 1 Clinical and functional characteristics of COPD patients with and without nonanemic iron deficiency (NAID)

Clinical and functional variables	All patients (N=36)	NAID COPD (N=18)	Non-NAID COPD controls (N=18)
Clinical characteristics
Male/female, n	21/15	10/8	11/7
Age, years	66 (7)	67 (6)	64 (7)
Current smokers, n (%)	19 (52)	9 (50)	10 (55)
Body mass index, kg/m^2	24 (4)	24 (3)	25 (4)
Fat-free mass index, kg/m^2	16 (2)	15 (1)	16 (1)
CAT score	16 (8)	17 (9)	15 (7)
AECOPD ≥2/year, n (%)	10 (27)	5 (27)	5 (27)
Charlson index [median (P5–95)]	2 (2.1–2.6)	2 (2.1–2.6)	2 (2.2–2.5)
Treatment, n
LABD	36	18	18
ICS	8	4	4
Beta-blockers	3	1	2
Aspirin	3	1	2
Statins	4	2	2
Pulmonary function
FEV1/FVC, %	43 (12)	44 (13)	43 (12)
FEV1, % predicted	41 (16)	40 (16)	42 (22)
DLco, % predicted	47 (14)	46 (14)	49 (15)
PaO2, mmHg	70 (11)	67 (11)	72 (10)
PaCO2, mmHg	42 (6)	42 (5)	42 (6)
IC/TLC	0.28 (0.09)	0.28 (0.08)	0.29 (0.11)
QMVC, kg	37 (13)	35 (11)	40 (15)
Hematological characteristics
Hemoglobin, g/dL		14.5 (1)	15.2 (1)
MCV (fL)		90 (5)	92 (4)
MCHC (g/dL)		32 (1)	33 (1)
Transferrin saturation, %		20 (5)	40 (3)*
Ferritin, ng/mL		70 (27)	235 (39)*
C-reactive protein, mg/dL		0.6 (1)	0.7 (0.9)
Daily physical activity
Steps per day	5,726 (3,337)	4,402 (2,145)	6,975 (3,813)**
Physical activity level	1.49 (0.2)	1.39 (0.1)	1.59 (0.2)***
Moderate physical activity, min/day	103 (80)	85 (80)	120 (78)
Moderate activity per day, % of patients	83	66	100†
Time spent sitting, min/day	397 (196)	448 (184)	342 (201)
Prolonged time spent sitting, % of patients	55	73	37††

Notes: Data are presented as mean (SD) unless otherwise stated. Moderate physical activity per day: at least 30 minutes; prolonged time spent sitting per day: >6 hours.

* P<0.001;

** P=0.020;

*** P=0.019;

† P=0.010;

†† P=0.048.

Abbreviations: AECOPD, acute exacerbation of chronic obstructive pulmonary disease; CAT, chronic obstructive pulmonary disease assessment test; DLco, carbon monoxide diffusing capacity; FEV₁/FVC, forced expiratory volume at 1 second/forced vital capacity; ICS, inhaled corticosteroid; IC/TLC, inspiratory capacity/total lung capacity; LABD, long-acting bronchodilators; MCV, mean corpuscular volume; MCHC, mean corpuscular hemoglobin concentration; PaCO₂, carbon dioxide arterial pressure; PaO₂, oxygen arterial pressure; QMVC, quadriceps maximal strength during maximum voluntary contraction.