Table 3.

Summary of meta-analyses of risk estimates in studies with homogenous measures of exposure and in the subsetof higher quality studies (high completeness of reporting and lower likelihood of bias and confounding).

Exposure	Meta-analysis	Number of Risk estimates	Meta risk estimate	Confidence intervals	Test for heterogeneity
Three shift schedule
	All studies	7	1.12	0.96 - 1.30	Q=5.1, p=0.53
	Better studies	7	1.12	0.96 - 1.30	Q=5.1, p=0.53
Fixed night work
	All studies	5	1.51	1.27 – 1.78	Q=3.65, p=0.46
	Better studies	5	1.51	1.27 – 1.78	Q=3,65, p=0.46
Working hours
> 40 h/wk	All studies	10	1.36	1.25 – 1.49	Q=22.2, p=0.02
	Better studies	3	1.17	0.80 – 1.71	Q=9.60, p=0.008
Lifting >100 kg/d	All studies	10	1.32	0.93 – 1.87	Q=25.4, p=0.002
	Better studies	5	1.02	0.73 – 1.44	Q=7.8, p=0.10
Standing >6 h/d
	All studies	6	1.16	1.01 – 1.32	Q=8.9, p=0.11
	Better studies	(2)	(1.26)	(0.83 – 1.96)	Q=2.9, p=0.09