Table 3. Association between metformin and back pain considering body mass index classification.

Body Mass Index
	Normal			Overweight			Obese
	OR (95% CI)	p value	n	OR (95% CI)	p value	n	OR (95% CI)	p value	n
Whole cohort
Cases/no-cases	310/1,589			1,399/5,650			3,196/8,458
Unadjusted	0.83 (0.65–1.06)	0.14	1,899	0.90 (0.80–1.01)	0.08	7,049	0.91 (0.84–0.99)	0.03	11,654
Adjusted	0.83 (0.65–1.07)	0.18	1,831	0.89 (0.79–1.01)	0.07	6,808	0.90 (0.86–0.98)	0.02	11,321
Females
Cases/no-cases	109/582			472/1,573			1,468/3,149
Unadjusted	0.97 (0.64–1.47)	0.91	691	0.88 (0.71–1.08)	0.23	2,045	0.90 (0.80–1.02)	0.12	4,617
Adjusted	0.97 (0.65–1.48)	0.91	673	0.87 (0.70–1.08)	0.22	1,978	0.90 (0.80–1.03)	0.13	4,480
Males
Cases/no-cases	201/1,007			927/4,077			1728/5,309
Unadjusted	0.76 (0.56–1.03)	0.08	1,208	0.90 (0.78–1.04)	0.19	5,004	0.93 (0.83–1.04)	0.21	7,037
Adjusted	0.76 (0.56–1.05)	0.10	1,158	0.90 (0.78–1.04)	0.17	4,830	0.91 (0.81–1.02)	0.12	6,841

CI: confidence interval, OR: Odds ratio, Case/no-cases of chronic back pain

^a Adjusted for education, smoking status, cardiovascular and mental health conditions.

Statistical significance: p<0.05