Systematic review with meta-analysis of the epidemiological evidence relating smoking to type 2 diabetes

Table 1 Literature searching

Step		Papers originally selected as probably relevant1	Papers rejected during data entry2	Papers providing separate results for multiple studies3
1	Previous reviews	98	10	3[9-11]
2	Medline search	74 (from 3365 hits)	23	4[12-15]
3	In-house database	1	0	0
4	Embase search	33 (from 5433 hits)	7	0
5	Secondary references4	15 (of 30 identified)	2	0
Total		221	42	7

¹Numbers of papers originally selected exclude those already identified in a previous step.

²Reasons for rejection are summarized in Supplementary file 1.

³Or for separate periods of follow-up.

⁴From papers identified in steps 2 to 4.