TABLE 2.

Summary of the studies included in systematic review and meta-analysis

First author [ref.]	Country/region	Study period	Study design	Radon detection technique	Sex	Population source	Outcome: LC diagnosis/death	Never-smokers		Ever-smokers
								Cases	Controls	Cases	Controls
Darby[48]#¶ Darby[51]#¶	Europe	1960–99	Pooled study		M/F	General+hospital	Diagnosis	884	5418	6040	8252
Oberaigner[25]	Austria	1970–92	C-C		M/F	General	Diagnosis	22	41	159	127
Tomasek[26]	Czechia	1960–99	Cohort	Kodak LR115	M/F	General	Death	28	295	143	417
Auvinen [27]	Finland	1986–92	C-C	Alpha track	M/F	General	Diagnosis	44	229	772	752
Ruosteenoja[28]	Finland	1979–85	C-C	Radon dosimeter	M	General	Diagnosis	3	33	155	291
Baysson[29]	France	1990–99	C-C	Kodalpha LR115	M/F	Hospital	Diagnosis	44	344	521	797
Kreuzer[30]	Germany: eastern	1991–97	C-C	Alpha track	M/F	General	Diagnosis	96	544	850	994
Kreienbrock[31]	Germany: western	1990–95	C-C	Solid-state nuclear track	M/F	General	Diagnosis	89	653	1225	1433
Bochicchio[32]	Italy	1993–96	C-C	Radon dosimeter	M/F	Hospital	Diagnosis	28	102	355	291
Barros-Dios [33]	Spain	1992–94	C-C	Alpha track	M/F	General	Diagnosis	12	94	144	133
Pershagen[34]	Sweden	1980–84	C-C	Solid-state alpha track	M/F	General	Diagnosis	175	1156	682	761
Lagarde[35]	Sweden	1978–95	C-C	Radon dosimeter	M/F	General	Diagnosis	258	487
Pershagen[44]	Sweden: Stockholm	1983–87	C-C	Alpha track	F	General+hospital	Diagnosis	36	181	160	194
Darby[36]	England	1988–95	C-C	Small passive radon	M/F	General+hospital	Diagnosis	26	896	874	2062
Krewski[49]#¶ Krewski[50]#¶	North America	1982–97	Pooled study		M/F	General	Diagnosis	659	2185	2930	2681
Schoenberg[37]	USA: New Jersey	1982–84	C-C	Alpha track	F	General	Diagnosis	61	213	372	189
Letourneau[38]	Canada: Winnipeg	1983–90	C-C	CR-39 alpha track	M/F	General	Diagnosis	24	224	509	498
Alavanja[39]	USA: Missouri	1986–92	C-C	Alpha track	F	General	Diagnosis	377	983	161	200
Alavanja[45]	USA: Missouri	1993–94	C-C	CR-39 alpha-particle	F	General	Diagnosis	31	62	471	480
Field[40]	USA: Iowa	1993–97	C-C	Alpha track	F	General	Diagnosis	56	414	357	200
Sandler[65]	USA: Connecticut	1989–92	C-C	Alpha track etch	M/F	General	Diagnosis	54	78	718	735
Sandler[65]	USA: Utah	1989–92	C-C	Alpha track etch	M/F	General	Diagnosis	56	211	342	379
Lubin[46]#¶ Lubin[47]#¶	China	1985–98	Pooled study		M/F	General	Diagnosis	322+	708+	706	1266
Blot[42]	China: Shenyang	1985–87	C-C	Radon dosimeter	F	General	Diagnosis	113	213	162	120
Wang[43]	China: Gansu	1994–98	C-C	Alpha track	M/F	General	Diagnosis	209	495	544	1146
Lorenzo-Gonzalez [52]#§	Spain: northwest	2003–13	Pooled study	Alpha track	M/F	Hospital	Diagnosis	476+	656+	261f	264f
Barros-Dios [66]¶	Spain: Galicia	2004–08	C-C	Alpha track	M/F	Hospital	Diagnosis	47	220	261	264
Torres-Duran [64]##	Spain: Galicia	2011–13	C-C	Alpha track	M/F	Hospital	Diagnosis	192	329
Wilcox[68]¶¶	USA: New Jersey	1989–92	C-C	Alpha track	M/F	General	Diagnosis	40	116	521	513
Turner[67]¶¶	USA	1982–88	Cohort	Mean county-level of radon	M/F	General	Death	271	375 087	2733	355 286

Data are presented as n. LC: lung cancer; C-C: case–control study; M: male; F: female. ^#: these studies are included in the meta-analysis for never-smokers; ^¶: these studies are included in the meta-analysis for ever-smokers; ⁺: unpublished data provided by original investigators; ^§: this study has been revised by its lead investigator to exclude the results of Barros-Dios [33] which was included in the Darby [48] pooled study; ^ƒ: data for ever-smokers extracted from Barros-Dios [66] which was not analysed in the pooled study; ^##: this study has been updated from July 2013 by its lead investigator to include more cases and controls in the Lorenzo-Gonzalez [52] pooling study; ^¶¶: these studies are not included in the meta-analysis due to different measures of effect (cohort study) or standard errors or confidence intervals (case–control study) not reported for their risk estimates.