Total Antioxidant Status in Stable Chronic Obstructive Pulmonary Disease

Figures & data

Table 1 Baseline Characteristics of COPD Patients and Controls

		COPD Patients (n=90)	Controls (n=30)	P-value
Age, years [Mean (SD)]		67 (9)	66 (4)	0.27*
Male sex, n (%)		67 (74.4)	20 (66.7)	0.41^‡
BMI, kg/m^2 [Mean (SD)]		28.7 (6.7)	27.2 (3.2)	0.23*
Smoking status current	Light, n (%)	19 (21)	18 (60)	<0.001^‡
	Heavy	39 (43)	4 (13)
Former		32 (36)	8 (27)
Pack-years [Median (IQR)]		43 (33−55)	41 (17.3–48)	0.27^†
CRP, mg/L [Median (IQR)]		2.6 (1.4–6.2)	2.2 (0.97–3.15)	0.08^†
FEV1/FVC ratio [Median (IQR)]		0.61 (0.46–0.68)	0.795 (0.75–0.83)	<0.001^†
FEV1 predicted, % [Median (IQR)]		64 (42 − 88)	105.5 (99–113.3)	<0.001^†
Exacerbations in the previous year, n (%)
Non-exacerbators (0)		44 (49)	–	–
Infrequent exacerbators (1)		37 (41)	–	–
Frequent exacerbators (≥2)		9 (10)	–	–
Time since the last exacerbation, months [Median (IQR)]		5 (3–8.3)	–	–
TAS, mmol/L [Median (IQR)]		1.68 (1.55–1.80)	1.59 (1.54–1.68)	0.03^†

Notes: *Student’s T-test; ^†Mann–Whitney U-test; ^‡χ² test; SD, standard deviation; IQR, inter quartile range. The values written in bold were statistically significant at the level of P < 0.05.

Abbreviations: BMI, body mass index; light smoking, <20 pack-years; heavy smoking, ≥20 pack-years; pack-years, number of cigarettes per day x number of smoking years/20; CRP, C-reactive protein; FEV₁/FVC ratio, forced expiratory volume in one second/forced vital capacity ratio; FEV₁, forced expiratory volume in one second; TAS, total antioxidant status.

Table 2 Baseline Characteristics of COPD Patients, According to Airflow Obstruction Severity

		Mild (n=30)	Moderate (n=30)	Severe/Very Severe (n=30)	P-value
Age, years [Mean (SD)]		66 (59–70)	68 (62–72)	71 (65–78)	0.01*
Male sex, n (%)		20 (66.7)	22 (73.3)	25 (83.3)	0.41^†
BMI, kg/m^2 [Mean (SD)]		29.4 (26.9–31.7)	31.7 (25.9–35)	24 (19.9–29.2)	<0.001*
Smoking status current	Light, n (%)	10 (33)	7 (23)	2 (7)	<0.001^†
	Heavy	14 (47)	9 (30)	16 (53)
Former		6 (20)	14 (47)	12 (40)
Pack-years [Median (IQR)]		40.5 (31.8–52.5)	43 (27.6–51)	49 (41.5–73.88)	0.15*
CRP, mg/L [Median (IQR)]		2.6 (1.3–4.6)	2.5 (1.6–6.2)	2.95 (1.3–7.73)	0.69*
FEV1/FVC ratio [Median (IQR)]		0.68 (0.668–0.69)	0.645 (0.568–0.68)	0.41 (0.34–0.48)	<0.001*^‡
FEV1 predicted, % [Median (IQR)]		93.5 (87.8–103.5)	64 (56–69.25)	37 (31–42.75)	<0.001*^‡
Exacerbations in the previous year, n (%)
Non-exacerbators (0)		22 (73)	17 (57)	5 (17)	<0.001^†
Infrequent exacerbators (1)		7 (23)	12 (40)	18 (60)
Frequent exacerbators (≥2)		1 (3)	1 (3)	7 (23)
Time since the last exacerbation, months [Median (IQR)]		6.5 (4.3–9.3)	5 (3 − 8)	5 (3.5–8.5)	0.70*
TAS, mmol/L [Median (IQR)]		1.60 (1.52–1.79)	1.70 (1.58–1.80)	1.70 (1.59–1.80)	0.52*

Notes: *Kruskal–Wallis test (Post hoc Conover); ^†χ² test; SD, standard deviation; ^‡At the level P < 0.05 there was a significant difference between mild vs moderate, mild vs severe/very severe, moderate vs severe/very severe; IQR, inter quartile range. The values written in bold were statistically significant at the level of P < 0.05.

Abbreviations: BMI, body mass index; light smoking, <20 pack-years; heavy smoking, ≥20 pack-years; pack-years, number of cigarettes per day x number of smoking years/20; CRP, C-reactive protein; FEV₁/FVC ratio, forced expiratory volume in one second/forced vital capacity ratio; FEV₁, forced expiratory volume in one second; TAS, total antioxidant status.

Table 3 TAS Value in COPD, According to Smoking Status, Pack-Years, Exacerbations in the Previous Year and Hypercapnia

	Median Range (25–75%)	P-value
	TAS (mmol/L)
Non-smokers (n=19)	1.62 (1.51–1.80)	0.71*
Current smokers (n=32)	1.68 (1.58–1.77)
Former smokers (n=39)	1.70 (1.55–1.80)
Pack-years: light (n=19)	1.52 (1.13–1.51)	0.05^†
Heavy (n=39)	1.70 (1.60–1.79)
Exacerbations: non-exacerbators (n=44)	1.72 (1.52–1.80)	0.45*
Infrequent exacerbators (n=37)	1.65 (1.58–1.79)
Frequent exacerbators (n=9)	1.68 (1.52–1.70)
Pk CO2 (kPa): normocapnia (n=75)	1.70 (1.18 − 1.80)	0.43^†
Hypercapnia (n=6)	1.61 (1.49 − 1.88)

Notes: *Kruskal–Wallis test; ^†Mann–Whitney U-test.

Abbreviations: TAS, total antioxidant status; pack-years, number of cigarettes per day x number of smoking years/20; light smoking, <20 pack-years; heavy smoking, ≥20 pack-years; exacerbators, infrequent 1, frequent ≥2 in the previous year; P_k CO₂, capillary carbon dioxide partial pressure; hypercapnia, P_k CO₂ > 6.38 kPa (reference range 4.66–6.38 kPa).

Figure 1 Correlation between pack-years and TAS With Spearman’s rank correlation coefficient Rho we found a significant positive correlation between (A) pack-years and TAS in all participants (Rho = 0.429, P = 0.004) and (B) COPD patients (Rho = 0.359, P = 0.02), (C) but not in controls (Rho = 0.800, P = 0.01).

Abbreviations: Pack-years, number of cigarette per day x number of smoking years/20; TAS, total antioxidant status.