Sports-related concussion increases the risk of subsequent injury by about 50% in elite male football players Anna Nordström, 1 Peter Nordström, 2 Jan Ekstrand 3 1 Department of Surgical and Perioperative Sciences, Sports Medicine, Umeå University, Umeå, Sweden 2 Department of Community Medicine and Rehabilitation, Geriatric Medicine, Umeå University, Umeå, Sweden 3 Football Research Group, Division of Community Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden Correspondence to Dr Anna Nordström, Department of Surgical and Perioperative Sciences, Sports Medicine, Umeå University, Umeå 901 85, Sweden; anna.nordstrom@idrott.umu.se Accepted 15 July 2014 Published Online First 31 July 2014 To cite: Nordström A, Nordström P, Ekstrand J. Br J Sports Med 2014;48: 1447–1450. ABSTRACT Background Little is known about the short-term and long-term sequelae of concussion, and about when athletes who have sustained such injuries can safely return to play. Purpose To examine whether sports-related concussion increases the risk of subsequent injury in elite male football players. Study design Prospective cohort study. Methods Injuries were registered for 46 male elite football teams in 10 European countries in the 2001/ 2002–2011/2102 seasons. Two survival models were used to analyse whether concussion increased the subsequent risk of an injury in the first year. Results During the follow-up period, 66 players sustained concussions and 1599 players sustained other injuries. Compared with the risk following other injuries, concussion was associated with a progressively increased risk of a subsequent injury in the first year (0 to <3 months, HR=1.56, 95% CI 1.09 to 2.23; 3 to <6 months, HR=2.78, 95% CI 1.58 to 4.89; 6–12 months, HR=4.07, 95% CI 2.14 to 7.76). In the second model, after adjustment for the number of injuries in the year preceding the concussion, this injury remained significantly associated with the risk of subsequent injury in the first year (HR=1.47, 95% CI 1.05 to 2.05). Conclusions Concussion was a risk factor for sustaining subsequent injury within the following year. In-depth medical evaluation, which includes neurological and cognitive assessment, is warranted within the concussion management and return-to- play process. INTRODUCTION Sports are a major cause of concussion, often referred to as mild traumatic brain injury within general medicine. 1 Despite an estimated annual incidence of 1.6–3.8 million sports-related concus- sions in the USA alone, very little is known about the consequences of early return to play following such injuries. 2–4 Traditionally, contact sports such as boxing, rugby union and American football have been asso- ciated with a high risk of concussion. 5 Recently, awareness of the potential consequences of head injuries has increased within other contact sports, such as football (used synonymously with ‘soccer’ in this paper unless specified), the most popular sport in the world with more than 265 million players. 6 Studies have investigated the incidence of concussion in football players of different ages, genders and participation levels. In general, the risk of concussion appears to be increasing over time, 78 and more than half of the players in some football leagues have a history of concussion, or symptoms corresponding to this type of injury. 9 Other researchers have reported that head injuries com- prise 4–22% of all football injuries. 10 In the short-term recovery period, concussion has been associated with at least short-term cogni- tive impairments affecting patients’ attention, executive function and visuospatial skills. 11 This mild degree of cognitive impairment may make the player more vulnerable to injuries in the first weeks after trauma. Consistent with such risks after sports concussion, men in the general population who have reduced cognitive function are at increased risk of concussion and more severe head injuries than their cognitively normal peers. 12 13 The primary aim of this study was to examine the risk of subsequent injury after return to play in football players who had sustained concussions. MATERIALS AND METHODS This study is part of the on-going Union of European Football Associations (UEFA) Champions League injury study, which is a long-term prospect- ive observational cohort study of the highest level of professional European football players. In short, 46 senior professional male football teams from the top divisions in 10 European countries were fol- lowed prospectively for 172 team-seasons (1–11 seasons) between July 2001 and June 2012. The teams’ squad consisted of 28±8 players (range 15– 57) with a mean age of 26±1 (range 22–30 years). The registration of exposure to, and occurrence of, injuries has been detailed previously. 14 15 The study design followed the consensus guidelines for defini- tions and data collection procedures for studies of football injuries outlined by the UEFA 14 and in the consensus document for football injury surveillance studies. 16 Based on type, injuries were diagnosed and registered in the injury database by each team, and classified as gradual onset (eg, tendinopathy, stress fracture and musculoskeletal pain) or sudden onset (eg, fractures, contusions, ligament sprains and muscle strains). All injuries preventing players from participating fully in training or matches were recorded. Players were considered to be injured until medical staff had cleared them for full participation in training and availability for match selection. The local ethics committee of Linköping University approved the study protocol. Editor’s choice Scan to access more free content Nordström A, et al. 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