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Lumbar disc herniation (LDH) is most common in men aged 20-40 at the L4/5 level; however, left-right differences have not been reported. Improving our understanding of left- and right-side LDH may facilitate the estimation of mechanical load on intervertebral discs. Here, we assessed left-right differences in LDH via a retrospective analysis of LDH cases.Among 10,972 surgical cases of LDH identified in the Nagoya Spine Group database, 2899 in which right- and left-LDH sides were observable in a single vertebral segment were identified (mean age 46.3 ± 16.6 years, 2028 males). The following characteristics of patients with right- and left-LDH were compared: age, LDH level, surgical technique, operative time, blood loss, length of hospital stay, preoperative Japan Orthopaedic Association (JOA) score, and JOA recovery rate.LDH occurred on the right and left sides in 1358 and 1541 patients, respectively, with patients with right-side LDH significantly older than those with left (47.9 ± 16.6 versus 45.0 ± 16.5, respectively; p 0.001). No between-group differences in sex, age, LDH level, surgical technique, operative time, blood loss, length of hospital stay, preoperative JOA score, or JOA recovery rate were observed. The occurrence of right-side LDH increased with age, occurring in 42.7%, 45.1%, 49.9%, and 54.7% of patients aged 10-29, 30-49, 50-69, and 70-89 years, respectively.Left-side LDH was observed more frequently than right; however, right-side LDH incidence increased with age. No significant between-group differences regarding symptoms, treatments, or outcomes were observed.