Effects of Competition Level on the Prevalence and Incidence of Lumbar Disk Degeneration in Japanese Collegiate Gymnasts

BACKGROUND: Lumbar disk degeneration (LDD) occurs frequently in athletes. Researchers have found that LDD occurs mainly in the lower disks (L4/L5 and L5/S1) in the general and athletic populations. However, a retrospective study showed a high prevalence of LDD in the upper lumbar disks (L1/L2), especially in elite gymnasts. PURPOSE: To investigate the effect of competition level on the prevalence and incidence of LDD in the upper lumbar disks (L1/L2). STUDY DESIGN: Cross-sectional study; Level of evidence, 3; and cohort study; Level of evidence, 2. METHODS: We conducted 2 studies to evaluate the effect of competition level on the prevalence and incidence of LDD in Japanese collegiate gymnasts. In study 1, a cross-sectional study of 298 collegiate gymnasts was conducted between 2011 and 2015. Competition levels were categorized as regional, national, and international, and T2-weighted magnetic resonance imaging (MRI) was used to evaluate LDD. Chi-square testing was applied to assess differences in the prevalence of LDD and spinal levels among the 3 competition levels. In study 2–-a prospective cohort study–-LDD progression and its related risk factors were investigated in 51 collegiate gymnasts. Baseline lumbar MRI scans and measurements of physical function (generalized joint laxity and finger-floor distance test) were performed in March 2014. Follow-up lumbar MRI scans were obtained 2 years later, in February 2016. Logistic regression analyses were performed to investigate the relationship between competition level and LDD progression. RESULTS: In study 1, the prevalence of at least 1 degenerated disk in the regional, national, and international groups was 44.2% (19/43), 44.7% (98/219), and 52.8% (19/36), respectively (P = .655). The prevalence of LDD at L1/L2 in the international group was significantly higher than that in the other 2 groups (P = .018). In study 2, the presence of LDD at L1/L2 was associated significantly with international-level competition (adjusted odds ratio, 47.8; 95% CI, 2.75-830.50). CONCLUSION: In Japanese collegiate gymnasts, competing at the international level was found to be a risk factor for LDD at L1/L2.