Table 4. Association between metformin and back pain considering age classification.

Age
	40–50 years			50–60 years			60–72 years
	OR (95% CI)	p value	n	OR (95% CI)	p value	n	OR (95% CI)	p value	n
Whole cohort
Cases/no-cases	470/1,636			1,633/4,956			2,852/9,239
Unadjusted	0.97 (0.78–1.20)	0.78	2,106	0.98 (0.88–1.10)	0.85	6,589	0.90 (0.82–0.98)	0.01	1,2091
Adjusted	0.92 (0.74–1.14)	0.45	2,022	0.94 (0.83–1.06)	0.32	6,345	0.85 (0.78–0.93)	0.01	1,1593
Females
Cases/no-cases	214/547			716/1,714			1,135/5,343
Unadjusted	1.00 (0.72–1.38)	0. 97	761	1.07 (0.90–1.28)	0.41	2,430	0.83 (0.73–0.96)	0.01	4,217
Adjusted	0.88 (0.62–1.24)	0.47	728	1.02 (0.85–1.23)	0.78	2,345	0.83 (0.72–0.95)	0.01	4,058
Males
Cases/no-cases	256/1,089			917/3,242			1,717/6,157
Unadjusted	0.98 (0.74–1.31)	0.93	1,345	0.94 (0.81–1.09)	0.43	4,159	0.93 (0.84–1.04)	0.24	7,874
Adjusted	0.97 (0.72–1.31)	0.85	1,294	0.90 (0.77–1.08)	0.21	4,000	0.87 (0.78–0.97)	0.02	7,535

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

^a Adjusted for BMI (continuous), education, smoking status, cardiovascular and mental health conditions.

Statistical significance: p<0.05