Table 3.

Time trend for improvements in low back pain

	Intervention group (n=23)					Control group (n=28)
	IRR*	95%CI		p value		IRR*	95%CI		p value
* Incident rate ratio. The number of workers in the intervention group is 301 and the number of workers in the contorl group is 315.
1-3 months	reference					reference
4-6 months	0.44	0.22	0.89	0.021		0.52	0.26	1.05	0.068
7-10 months	0.46	0.24	0.90	0.023		0.59	0.32	1.09	0.090
trend	0.90	0.81	0.99	0.034		0.92	0.84	1.02	0.101