Introduction Findings of disc degeneration (DD) on magnetic resonance imaging (MRI) are frequently seen in asymptomatic individuals with increasing prevalence with age. DD developing in early adulthood seems to predispose the individual for a more rapid progression of degeneration. Although disc degeneration, protrusion, bulge, and extrusion have been associated with LBP, the value of MRI findings in predicting future LBP has proven low.

Our knowledge on the natural history of the intervertebral disc (IVD) is insufficient to differentiate age-related changes from possible pathologic findings. The few long-term studies including MRI published to date either lack clinical information or report on specific populations or older subjects. In the present study, our objective was 1) to describe the natural history of lumbar IVDs from childhood to adulthood, and 2) to investigate whether findings of DD were associated with LBP.

Methods Ninety-four healthy school children were randomly recruited in 1994 to a longitudinal study including a semi-structured interview, a clinical examination and lumbar spine MRI at the age of 8, 11 and 18. In January 2021, all those subjects who could be reached (n=89) were invited to take part in this long-term follow-up including a semi-structured interview, a clinical examination and a lumbar spine MRI (high-field 1.5T MRI with a dedicated spine coil). Three lowest IVDs were assessed using a Pfirrmann summary score, and the ratio of signal intensity of the disc to signal intensity of the adjacent cerebrospinal fluid (SINDL). The association of disc changes at any age with self-reported LBP at the age of 34 was analyzed. 

Results Fourty-eight subjects consented to this long-term follow-up at the mean age of 34.2 years (SD 0.6). Thirty-five of them reported LBP without specific trauma. The Pfirrmann summary score significantly increased with age (p<0.001). Subjects reporting LBP at the age of 34 demonstrated statistically significantly higher summary scores both at the age of 18 and 34 compared to asymptomatic subjects (p=0.004 at age 18, and p=0.039 at age 34). SINDL significantly decreased with age (p<0.001 for all levels separately), but no significant differences between subjects with or without LBP at the age of 34 were observed.

Discussion Our main finding was that subjects who reported LBP at the age of 34 had statistically significantly higher Pfirrmann summary scores already at the age of 18. The difference remained statistically significant at the age of 34, although progression of DD was seen in the asymptomatic subjects alike (Figure, error bars for 95% confidence intervals.). Hence, more severe DD in single IVD or more extensive DD in multiple IVDs after pubertal growth spurt may be associated with LBP in adulthood. When SINDL was calculated for each level separately, no statistically significant differences emerged between subjects with or without LBP at the age of 34 suggesting that changes in a single IVD may not be as consequential as more widespread DD. In conclusion, subjects with LBP at the age of 34 had more wide-spread or severe DD already at the age of 18 compared to asymptomatic subjects.