Joint association of cigarette smoking and PM2.5 with COPD among urban and rural adults in regional China

BMC Pulmonary Medicine

Table 1 Selected socio-demographic and anthropometric characteristics of participants in this study

	Total, n (%)	Never-smokers, n (%)	Smokers, n (%)^a
N of participants	3407	2073 (60.8)	1334 (39.2)
Mean age (deviation)	57.2 (9.9)	56.27 (9.8)	58.7 (9.7)
Age (years)
40–49	863 (25.3)	599 (28.9)	264 (19.8)
50–59	1129 (33.1)	698 (33.7)	431 (32.3)
60–69	1020 (29.9)	566 (27.3)	454 (34.0)
70+	395 (11.6)	210 (10.1)	185 (13.9)
Gender
Men	1561 (45.8)	334 (16.1)	1227 (92.0)
Women	1846 (54.2)	1739 (83.9)	107 (8.0)
Residence
Urban	1674 (49.1)	1002 (48.3)	672 (50.4)
Rural	1733 (50.9)	1071 (51.7)	662 (49.6)
Educational attainment (years)
9−	2780 (81.6)	1702 (82.1)	1078 (80.8)
10–12	510 (15.0)	301 (14.5)	209 (15.7)
13+	117 (3.4)	70 (3.4)	47 (3.5)
Occupation^b
Blue collar	2384 (70.0)	1523 (73.5)	861 (64.5)
White collar	1023 (30.0)	550 (26.5)	473 (35.5)
Annual mean PM2.5(μg/m³)^c
< 75	2267 (66.5)	1420 (68.5)	847 (63.5)
≥ 75	1140 (33.5)	653 (31.5)	487 (36.5)
Biomass use^d
No	2518 (73.9)	1558 (75.2)	960 (72.0)
Yes	889 (26.1)	515 (24.8)	374 (28.0)
Parental history of respiratory diseases^e
Negative	2321 (68.1)	1402 (67.6)	919 (68.9)
Positive	1086 (31.9)	671 (32.4)	415 (31.1)
Body weight status (BMI)^f
24−	1296 (38.0)	783 (37.8)	513 (38.5)
24–27	1501 (44.1)	920 (44.4)	581 (43.6)
28+	610 (17.9)	370 (17.8)	240 (18.0)

^aSmokers referred to either current (continuously smoked at least one cigarette every day for at least 1 year or totally smoked 18+ packs in a year) or former (met the criteria of current smokers previously but now did not smoke for > 1 year) smokers, while non-smokers means the never-smokers. Non-smokers were those not meeting the current/former smokers’ criteria
^bBlue collar: including farmer, factory worker, forestry worker, fisher, salesperson, houseworker and vehicle driver; White collar: including office worker, teacher, doctor, academic researcher and government official
^cClassification of PM2.5 was based on “ambient air quality standard (GB3095-2010)” issued by China State Department of Environment Protection in 2010
^dTypically using wood, grass, crop residues or animal waste for household cooking or heating
^ePositive parental history of respiratory diseases referred to that either of parents has been diagnosed with any of the following respiratory diseases: asthma, chronic bronchitis, emphysema, COPD, pulmonary heart disease, or bronchiectasis
^fBody weight status was assessed based on BMI cutoffs recommended for Chinese adults

ISSN: 1471-2466