Table 2.

Association between lumbar disc degeneration (LDD) sum score and low back pain (LBP)-related disability, stratified by mental distress and insomnia

Stratification	Unadjusted B (95% CI) (n = 927*)	Adjusted1 B (95% CI) (n = 843**)
1. Absence of both mental distress and insomnia	0.132 (0.044–0.221), p = 0.003 (n = 487)	0.132 (0.028–0.236), p = 0.013 (n = 456)
2. Isolated mental distress	0.236 (0.001–0.471), p = 0.049 (n = 75)	0.345 (0.039–0.650), p = 0.028 (n = 68)
3. Isolated insomnia	0.207 (0.068–0.346), p = 0.004 (n = 236)	0.207 (0.040–0.373), p = 0.015 (n = 212)
4. Co-occurring mental distress and insomnia	-0.075 (-0.267-0.116), p = 0.438 (n = 129)	-0.093 (-0.346-0.161), p = 0.470 (n = 107)

^{1: Adjusted for sex, smoking, body mass index, education, leisure-time physical activity, occupational physical exposure, Modic changes, and disc herniations}

^{B, beta coefficients; CI, Confidence interval}

^{Statistically significant values are bolded}

^{*Data on LDD, LBP-related disability, and on both insomnia and mental distress available}

^{**Full data available}