Physical conditions leading to medical discharge among Danish conscripts: a population-based study

Introduction Medical discharge during basic military training reduces readiness and training efficiency. In Denmark, diagnosis-specific evidence is limited, including differentiation between pre-existing conditions, overuse-related disorders and acute injuries. This study aimed to provide an International Classification of Diseases, 10th Revision (ICD-10)-informed profile of physical conditions leading to medical discharge in Danish conscripts and describe time to discharge. Methods Population-based registry study of male conscripts initiating compulsory service in Denmark (January 2019–December 2023). The primary reason for discharge was grouped into clinically meaningful categories informed by ICD-10. Musculoskeletal conditions were classified as pre-existing, acute traumatic or overuse-related; trauma prior to service/leave was recorded separately. Analyses were descriptive. Results Among 17 579 conscripts, 1499 (8.5%) were medically discharged. Of these, 827 (55.2%) were discharged due to physical conditions. Median age at enlistment was 20.4 years (IQR 19.7–21.8), and median service duration before discharge was 5.4 weeks (IQR 2.4–10.0). Musculoskeletal conditions accounted for 661 (79.9%) medical discharges for physical conditions, and other physical diagnoses for 166 (20.1%). Knee pain (n=229), back pain (n=166) and shoulder pain (n=49) were most frequent. Within musculoskeletal discharges, 33.9% were classified as pre-existing, 36.5% as overuse-related, 23.9% as acute traumatic and 5.8% as trauma prior to service/leave. Concussion was the most frequent non-musculoskeletal diagnosis (n=26). Mental health-related comorbidity was recorded in 4.4% of medical discharges for physical conditions, mainly alongside pre-existing or overuse-related musculoskeletal conditions. Conclusions Medical discharge for physical conditions in Danish conscripts was dominated by musculoskeletal conditions, most often classified as pre-existing or overuse-related rather than acute traumatic. An ICD-10-informed, discharge-focused classification may support baseline risk identification, earlier clinical recognition and selective modification of cumulative military load during the initial weeks of service as conscript intake increases.