A retrospective long-term follow-up study.To investigate the health-related quality of life (HRQOL) status in middle-aged patients with adolescent idiopathic scoliosis (AIS) treated non-surgically.The HRQOL status using various established questionnaires for non-operated AIS patients has not been fully investigated in long-term follow-up surveys.Inclusion criteria were non-surgical treatment for AIS, ≥ 30° major scoliosis at skeletal maturity (Risser grade ≥4), and age ≥ 30 years at the time of the survey. A total of 107 AIS patients were included and divided into three groups [single main thoracic (MT) curve group; n = 50, single thoracolumbar/lumbar (TL/L) curve group; n = 19, and double-major (DM) curve group; n = 38] based on curve location at skeletal maturity. Age- and sex-matched volunteers were selected as the control group.There were no significant differences in age at survey, body mass index, bone mineral density of the femoral neck, and skeletal muscle mass index among the groups. In all groups, major scoliosis progressed by approximately 0.5°/year from the time of skeletal maturity to the survey. The TL/L and DM groups showed significantly worse visual analog scale scores for low back pain compared to the MT group (p < 0.05). The all-scoliosis groups showed significantly worse scores for self-image domain of the SRS-22 than the control group (p < 0.0001). The TL/L group showed significantly worse scores for walking ability and social function domains of the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) (p < 0.05). There were no significant differences in Oswestory Disability Index and Short-Form-12 among the four groups.AIS patients with single MT curve maintain equal HRQOL status compared to healthy controls. Patients with structural TL/L curves are likely to experience greater annual TL/L curve progression and have substantial low back pain or worse low back pain-specific HRQOL status during middle age.4.