Incidence and Prevalence of Concussion in Denmark from 1999-2018: A Nationwide Cohort Study

Concussion is a common diagnosis in emergency rooms, yet contemporary incidence and prevalence estimates are sparse and rely on self-reported data. A nationwide cohort study was conducted to provide up-to-date information, covering the entire Danish population from 1999 to 2018. Hospital contacts with a concussion diagnosis, including emergency room visits, hospital admissions, and outpatient contacts, were retrieved from the Danish National Patient Registry (DNPR), and incidence rates were age-standardized and stratified. The 20-year prevalence was defined as the percentage of Danes alive in 2018 who had experienced a concussion since 1999. The diagnostic codes used were the ICD-10 code S06.0 and a local Danish code for 'observation for concussion' (DZ033D). Additional data on activities related to concussion injuries were obtained from the Accident Analysis Group at Odense University Hospital through DNPR. Findings from the study showed that during the period 1999-2018, the total age-standardized concussion incidence rate increased by 10% to 308 per 100,000 person-years (95% confidence interval CI: 304-313). Notable time trends included (1) a reduced sex difference from 40% to 6% (95% CI: 3%-9%), (2) a doubled incidence rate in children aged 0-1 and in seniors aged over 80, (3) an increased utilization of head imaging across all age groups, except children, (4) a decline in the proportion of traffic-related concussions, and (5) a prevalence of concussion of 4.9% (95% CI: 4.89%-4.93%) in 2018. The increasing incidence of concussions among the elderly is concerning in light of an aging population and warrants further investigation, as evidence-based preventive interventions for falls exist. In addition, the increased utilization of head imaging across all age groups except children calls for attention toward avoidance of unnecessary radiation exposure. Despite a drop in traffic-related cases, concussions remain highly prevalent. In conclusion, these findings indicate that concussions are an important public health concern, necessitating ongoing surveillance, research, and targeted resource allocation to address concussion management and prevention effectively.