Table 1. The baseline characteristics of all qualified studies in this meta-analysis.

First author	Disease type	Match	Ethnicity	Design	Age, years		Gender (Males, %)
					Cases	Controls	Cases	Controls
Zienolddiny S et al.	NSCLC	age, sex, smoking	Caucasian	population	60	60	76.99	76.14
Schwartz AG et al.	NSCLC	age, sex, race	Caucasian	population	NA	NA	NA	NA
Schwartz AG et al.	NSCLC	age, sex, race	African-American	population	NA	NA	NA	NA
Liu P et al.	lung cancer	NA	Caucasian	population	61.3	75.6	42.27	58.9
Liu P et al.	lung cancer	NA	Caucasian	population	64.6	57.1	56.1	54.9
Liu P et al.	lung cancer	NA	Caucasian	population	64.5	60.7	49.9	35.3
Spitz MR et al.	lung cancer	age, sex, race	Mixed*	population	NA	NA	NA	NA
Amos CI et al.	lung cancer	NA	Caucasian	hospital	62.1	61.1	57	56.6
Girard N et al.	lung cancer	age	Caucasian	population	NA	NA	NA	NA
Girard N et al.	lung cancer	age	Japanese	population	NA	NA	NA	NA
Broderick P et al.	lung cancer	NA	Caucasian	population	NA	NA	NA	NA
Shiraishi K et al.	lung cancer	NA	Japanese	hospital	60	50	73	60
Kohno T et al.	LSCC	sex, smoking	Japanese	hospital	62.7	62.5	90	57
Sakoda LC et al.	lung cancer	age, sex, smoking	Caucasian	population	NA	NA	67.3	66.6
Amos CI et al.	lung cancer	age, sex, race	African-American	hospital	62.4	55.7	54.82	41.24
Wu C et al.	lung cancer	age, sex	Chinese	hospital	NA	NA	69.3	31.1

Abbreviations: NSCLC, non-small-cell lung cancer; SLCC, lung squamous cell carcinoma; NA, not available.

^*Mixed ethnicity included Caucasian, African-American and Hispanic.