Association between tobacco exposure and bladder cancer recurrence: A systematic review and meta-analysis

Table 2 Assessment of quality of studies by the Newcastle–Ottawa scale

Ref.	Selection			Comparability			Outcome			Score
	1	2	3	4	5a	5b	6	7	8
Michalek et al[14], 1985	1	1	1	1	1		1	1		7
Grotenhuis et al[16], 2015	1	1	1	1	1	1	1	1		8
Wyszynski et al[25], 2014	1	1	1	1	1		1	1	1	8
Chen et al[19], 2007	1		1	1	1	1	1			6
Leibovici et al[20], 2005	1	1	1	1			1	1	1	7
Yuruk et al[26], 2017	1	1	1	1	1	1	1	1	1	9
van Osch et al[24], 2018	1	1	1		1	1	1	1	1	8
Ogihara et al[12], 2015	1	1		1	1	1	1	1	1	8
Rava et al[21], 2018	1		1	1	1	1	1	1		7
Hagiwara et al[11], 2013	1		1		1	1	1	1	1	7
Serretta et al[22], 2013	1		1	1	1		1	1	1	7
Serretta et al[23], 2020	1	1	1	1	1	1			1	7

1 = the exposed cohort is representative; 2 = Study cohort with unexposed; 3 = Exposure factor identified; 4 = No positive results at the start of the study; 5 = Cohort comparability based on design or analysis [(a) Study age controls; (b) Study controls for any additional factors); 6 = Outcome assessment is reliable; 7 = Follow-up time is long enough; 8 = Adequacy of cohort follow-up.