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.