Table 1.

Characteristics of the study population¹

	Non-Cases	Cases	P-value
Number of participants	70,839	428	-
Age at baseline (years)	52.3 ± 8.97	59.1 ± 8.58	<.0001
Education
Elementary school or less	20.4%	21.3%
Middle school	37.5%	38.9%
High school	28.3%	26.8%
Professional education/college or more	13.8%	13.0%	0.92
Income (per household)
<10,000 yuan	15.7%	15.6%
10,000-20,000 yuan	38.2%	34.9%
20,000-30,000 yuan	28.3%	31.4%
≥30,000 yuan	17.8%	17.9%	0.71
Occupation
Housewife	0.3%	0.2%
Professional workers	29.0%	30.5%
Clerical workers	20.7%	20.4%
Manual laborers	50.0%	48.9%	0.88
Family history
Any cancer	26.6%	28.7%	0.66
Lung cancer	4.9%	6.4%	0.18
Personal history of lung disease
Tuberculosis	5.5%	7.5%	0.61
Chronic bronchitis	7.3%	7.3%	0.75
Asthma	2.1%	3.5%	0.09
BMI (kg/m2)	24.0 ± 0.01	23.9 ± 0.16	0.38
Waist-to-hip ratio	0.810 ± 0.0002	0.811 ± 0.0025	0.86
Passive smoking
None	19.8%	20.8%
At home or in workplace	52.4%	48.5%
Both	27.9%	30.7%	0.79
Ever consumed alcohol	1.9%	1.0%	0.51
Ever consumed tea	29.5%	30.6%	0.15
Postmenopausal status	48.2%	49.3%	0.47
Supplement use
Any vitamin	19.6%	19.9%	0.62
Calcium-containing2	36.1%	31.8%	0.06
Vitamin D-containing2	20.2%	19.0%	0.05
Regular exercise3	35.0%	33.3%	0.81

¹Adjusted for age at baseline and presented as mean ± standard error or frequency (%), except for age at baseline where unadjusted mean ± standard deviation is shown.

²45 cases and 5,484 non-cases had missing information for calcium- and vitamin D-containing supplement use and were included in a separate category.

³Defined as at least once per week continuously for at least three months within the five years before the interview.