Effect of concussion on salary and employment: a population-based event time study using a quasi-experimental design

Peter Fallesen, Benito Campos, Peter Fallesen, Benito Campos

Abstract

Objective: Concussions are the most frequent traumatic brain injuries. Yet, the socioeconomic impact of concussions remains unclear. Socioeconomic effects of concussions on working-age adults were studied on a population scale.

Design: This population-based, event time study uses administrative data as well as hospital and emergency room records for the population of Denmark.

Setting: We study all Danish patients, aged 20-59 years, who were treated at a public hospital or at an emergency room between 2003 and 2017 after suffering a concussion without other intracranial or extracranial injuries (n=55 424 unique individuals). None of the patients had a prior diagnosis of intracranial or extracranial injuries within the past 10 years leading up to the incident.

Primary and secondary outcome measures: As primary endpoint, we investigate the mean effect of concussion on annual salaried income within a 5-year period after trauma. In an exploratory analysis, we study whether the potential impact of concussion on annual salaried income is driven by patient age, education or economic cycle.

Results: Concussion was associated with an average change in annual salary income of -€1223 (95% CI: -€1540 to -905, p<0.001) corresponding to a salary change of -4.2% (95% CI: -5.2% to -3.1 %). People between 30 and 39 years and those without high school degrees suffered the largest salary decreases. Affected individuals leaving the workforce drove the main part of the decrease. Absolute annual effect sizes were countercyclical to the unemployment rate.

Conclusions: Concussions have a large and long-lasting impact on salary and employment of working-age adults on a nationwide scale.

Keywords: health economics; neurosurgery; trauma management.

Conflict of interest statement

Competing interests: None declared.

© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY. Published by BMJ.

Figures

Figure 1
Figure 1
Estimated effect of concussions in percentage on salary for the exposure group measured against each control group. Note: figure shows the percentage change in salary experienced by the exposure group following their concussions compared with the expected trajectory absent the concussion (calculated from the control groups) with 95% CIs. See table 1 for separate p values for each estimate.
Figure 2
Figure 2
Salary development for exposure and control groups across time of exposure. Note: figure shows the salary trajectories for the exposure group (black) who suffers concussion at year 0 against normalised wage trajectories for the control groups who suffer their concussions 1–5 years later. Δ indicates the number of years between exposure and control incident. Table shows that there are no significant differences in the normalised salary levels for exposure and control group prior to exposure incident (see online supplemental figure S1, online supplemental digital content 3 for unnormalised salary trajectories).
Figure 3
Figure 3
(Left panel) The cumulative density function for salary post treatment among the treatment groups and their counterfactual outcome had they not experienced their concussions, and (right panel) the change in salary density for the exposure group compared with their counterfactual baseline expressed as the effect of concussion on the probability of earning below the salary level expressed on the x-axis following exposure event. Note: the figure shows the observed cumulative salary distribution following concussion for the exposure group (red) and the expected counterfactual salary distribution absent suffering concussion in the exposure group (blue), when using Δ=5 control group. The black line shows the difference between the observed and the counterfactual distribution, and the grey dash lines show the 95% CI. The close to constant decline of the difference between the two distributions as the salary increase indicates that the main part of the effect of concussions on salary is driven by people having a salary equal to 0.
Figure 4
Figure 4
Effect of concussion on salary across incident years and control groups together with the percentage fulltime unemployed of the labour force (LF). Note: figure shows annual estimates of concussion against each control group separately mapped against the share of the labour force that is full-time unemployed. 95% CIs. The estimates for the effect of concussion on salary almost uniformly increase in absolute magnitude when unemployment decreases, and decrease when unemployment increases, indicating that the effect of concussion on salary is countercyclical to the economic cycle.

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