Sickness absence > 14 days following sport-related traumatic brain injuries: a nationwide register-based study in Sweden.

Background: Sport-related traumatic brain injuries (SR-TBI) have received increasing concerns regarding potential long-term consequences. For adults in the general population, one of these consequences is inability to resume daily activities, most notably sickness absence (SA) from work. The aim of this study was to investigate how often SR-TBI is followed by a registered period of SA.

Methods: A nationwide register-based study was conducted. Source population: working aged individuals (18-63 years), living in Sweden during 2014-2016. Using the national patient register we included patients with a TBI diagnosis with the ICD-10 activity code 'while engaged in a sporting activity', excluding those with a TBI diagnosis in the preceding 365 days. Information on type of injury (e.g., concussion), cause of injury (e.g., falls, strikes by objects) and received healthcare (outpatient and/or inpatient) was collected. Basic sociodemographic variables were fetched from Statistics Sweden (age, sex, education level, marital status, type of living area, country of origin, receiving income from work). The Swedish Social Insurance Agency provided data on SA episodes lasting longer than 14 days. We calculated the incidence of new SA and estimated risk ratios (RRs) with 95% confidence intervals using modified Poisson regression (log link, robust variance) for both crude and multivariable models. Multinomial logistic regression assessed factors associated with SA duration (< 30 days, 30-90 days, > 90 days).

Results: 2826 individuals were identified. The majority (91%) had suffered a concussion. A new SA was found for 7% of the individuals with concussion and 32% for those with other intracranial injuries. Higher risk of a new SA was observed for other intracranial injuries compared to concussion (RR 2.76, 95% CI 2.15-3.53), inpatient care versus outpatient only (RR 1.92, 95% CI 1.50-2.46), and transport accidents versus strikes by living forces (RR 2.14, 95% CI 1.43-3.19). Higher odds for longer spells (> 90 days) were found for those with other forms of intracranial injuries than concussion, OR 10.20 (5.80-17.95) and those who had received inpatient healthcare, OR 3.68 (2.10-6.46).

Conclusion: The vast majority of all SR-TBIs are concussions and seldom followed by a new SA. For patients with other types of SR-TBI and for those who required inpatient healthcare a new, and often longer SA were more frequent. Additionally, injuries from transport-accidents (e.g., horseback riding, bicycling) elevated the risk of a new SA, potentially indicating the presence of other physical injuries.