Traumatic brain injury (TBI) is the leading cause of disability, limitations in daily living activities, and social participation among the young population worldwide.1–2 After TBI, low- to middle-income countries (LMICs) are known to have higher rates of hospital mortality and long-term functional impairments compared to high-income countries (HICs).3–5 Globally, studies confirm that individuals with milder TBI, higher education levels, and shorter stays in the Intensive Care Unit (ICU) have significantly higher survival rates and more favorable functional outcomes.6 Conversely, advanced age, lower Glasgow Coma Scale (GCS) scores, and the presence of subdural hematoma and/or intraventricular hemorrhage on cranial computed tomography (CT) scans are strongly associated with higher hospital mortality rates and long-term disabilities.7–9

In Brazil, TBI represents a significant and increasing public health concern, reflecting the challenges faced by LMICs.10–11 Its rising incidence is mainly related to socioeconomic factors and violence.12–13 Recent data report >131,000 TBI-related hospitalizations annually, with an incidence of 65.5 per 100,000 inhabitants14 and an estimated annual cost of $70 million.15–16 Functional outcomes are often poor as 25–50 % of survivors have unfavorable recovery six months post-injury,17 20 % remain dependent one year after severe TBI,18 and 68 % continue to experience disabilities five years later.19 Despite this burden, research on predictors of functional outcomes in the Brazilian population remains limited.

There are few studies in Brazil that investigated multiple predictors of functional outcomesat 617 and 12 months20,21,18,22 after sTBI. The findings suggested that low GCS scores,17 advanced age, trauma severity, and length of hospitalization were independent variables associated with functional outcomes.17,20 However, these studies present significant limitations such as a mixed sample composed of TBI and stroke cases,17 sample composed of only male individuals, and without differentiation of injury severity levels.20

Due to this gap in literature the functional trajectory after hospital discharge and many of the factors that influence the outcomes of severe TBI are still unknown. Elucidating the associations between clinical and sociodemographic variables and long-term functional outcomes in this population will be useful in guiding public policies for prevention and health promotion at national and regional levels. Based on this rationale, the hypothesis of this study is that clinical and sociodemographic factors are significant predictors of functional outcomes in individuals with sTBI within the first-year post-injury. Therefore, the present study aimed to investigate multiple predictors of functional outcomes within the first year after sTBI in Brazil.

This study was approved by the Research Ethics Committee of the Universidade Federal do Espírito Santo under the protocol number of 4.222.002. The Strengthening the reporting of observational studies in epidemiology (STROBE) guidelines were used to ensure the reporting of the study.

Between May 2021 and May 2022, 420 patients with sTBI were admitted to the State Hospital of Urgency and Emergency (HEUE). After applying the enrollment criteria, 172 (45 %) patients were included in the study. During follow-up, 27 individuals could not be contacted. Consequently, 145 individuals completed the 1-year follow-up (Fig. 1). Mortality rate due to sTBI within the first year was 15 % (n = 22) and 123 patients survived the first year after sTBI.

Fig. 1.

Flowchart of the study. TBI: Traumatic Brain Injury.

The 145 patients included in the functional outcome analysis were mostly male (85 %) with an average age of 45 (SD: 11) years. The principal causes of injury were falls (39.3 %) and being struck by a vehicle (pedestrian vs. auto) with 28.3 %. The majority of patients (57.9 %) had GCS scores ranging between 3 and 5 at hospital admission. Of the 145 individuals, 80 (55 %) had a low level of education and they spent an average of 11 (SD: ±8) days under mechanical ventilation assistance. Other sociodemographic and clinical characteristics are described in Table 1.

At hospital discharge, the majority (91 %) of patients had an unfavorable functional outcome (GOSE ≤ 6) and of these, 23 % were classified as lower severe disability while only (9 %) had a good functional recovery (GOSE of 7 or 8). Over the first year, this proportion reversed as the number of patients with GOSE scores ≤ 6 decreased and those with scores > 6 increased. Three months after TBI, the favorable outcome increased to 24 % of the sample, while unfavorable outcome decreased to 76 %. At 6 months, 38 % of patients had a favorable functional outcome, while 62 % had an unfavorable outcome. One year after the trauma, 48 % of patients had an unfavorable functional outcome, and 52 % had a good functional recovery. GOSE scores at hospital discharge, and at 3, 6, and 12 months after severe TBI and the trajectory of functional recovery over 12 months after severe TBI, are detailed in Figs. 2 and 3.

Fig. 2.

Glasgow Outcome Scale – Extended (GOSE) scores (1–8) at hospital discharge and 3, 6, and 12 months after severe traumatic brain injury. ↑ Upper. ↓ Lower.

Fig. 3.

Trajectory of functional recovery over 12 months after severe traumatic brain injury.

After individual analysis of the variables, age, sex, ISS score, performance of decompressive craniectomy, length of stay on mechanical ventilation support (MVS), and level of education were selected as potential predictors of mortality (Table 1).

In the final logistic regression model, being male (OR = 9.38, 95 %: CI 1.39, 62.97) and a greater length of stay on MVS (OR = 1.24, 95 % CI: 1.03, 1.48) were variables associated with a higher risk of an unfavorable functional outcome at hospital discharge. At 3 months post-trauma, an ISS score > 25 (OR = 3.37, 95 % CI: 1.26, 9.03), the performance of decompressive craniectomy (OR = 3.74, 95 % CI: 1.05, 13.33), greater length of stay on MVS (OR = 1.19 95 % CI: 1.07, 1.31), and low (OR = 4.45 95 % CI: 1.19, 16.57) and medium (OR = 7.42, 95 % CI: 1.77, 31.02) levels of education were predictors of functional outcome. At 6 months, only the performance of decompressive craniectomy (OR = 4.31, 95 % CI: 1.37, 13.58) and a greater length of stay on MVS (OR = 1.13, 95 % CI: 1.05, 1.21) were variables associated with a higher risk of a GOSE score ≤ 6. Finally, age > 65 years (OR = 4.96, 95 % CI: 1.12, 21.84), a greater length of stay on MVS (OR = 1.11, 95 % CI: 1.03, 1.13), and low (OR = 6.12, 95 % CI: 1.48, 25.16) and medium (OR = 6.49, 95 % CI: 1.49, 28.21) levels of education were associated with a higher risk of an unfavorable functional outcome 12 months after the trauma (Table 2).

This prospective study reveals a dynamic and evolving recovery process of individuals with severe TBI over the period of 1 year after the injury. Both at the time of hospital discharge and 3 months after the traumatic event, most patients showed significant levels of functional dependence, with approximately 20 % registering a high degree of disability. This high rate of disabilities in the acute phase is consistent with findings in other studies that evaluated short-term functional recovery.32–33 However, it can be observed that by reaching the 6-month mark, a significant portion of patients (38 %) showed a better outcome, with 19 % presenting moderate disability and another 19 % achieving complete recovery. This finding agrees with the results of previous studies with 6 months follow-up after sTBI,34–35 although it diverges from the findings of a previous study conducted in Brazil where functional recovery levels were higher in the first 3 months.18 As the follow-up extended to the 12-month period, there was a notable increase in the number of individuals who achieved total or good recovery, indicating that, over time, a substantial portion of patients with severe TBI showed significant improvement in their functionality and independence and those results are in line with previous studies that have conducted long-term follow-ups.36–37

Age above 65 was a strong predictor of an unfavorable functional outcome 12 months after the traumatic event. Other studies found similar results, with an almost linear relationship between advanced age and functional outcome on the GOSE after 6 months,8,38 and 12 months postinjury.39 In line with the present study’s results, a previous study did not find an association between age and functional outcomes at 3 months.40 Moreover, despite most patients being male, sex was not a predictor of hospital mortality nor long-term functional recovery, only showing as a predictive factor for functional outcome at the time of hospital discharge. This finding supports previous findings where age and sex were not associated with functional recovery 24 months post-trauma,41 which suggests that in the long term, the level of independence of these patients may be explained by other factors besides demographic ones.42

Regarding trauma severity indices, ISS scores >25 were associated with a higher risk of unfavorable outcomes at 3 months post-TBI. Although trauma severity indices are widely used in predicting hospital outcomes, few studies have included this variable in the final regression model. Other clinical factors such as GCS score at admission,37 length of ICU stay,18 time to obey commands,39 and changes in cranial CT scans43 were reported in previous studies, suggesting they have greater predictive potential for functional outcomes after severe TBI.

The performance of decompressive craniectomy was a predictor of worse functional outcome at 3- and 6-months post-trauma. This finding diverges from results found in previous studies,44–45 where decompressive craniectomy in cases of acute subdural hematoma post-TBI increased the chances of a favorable functional outcome. Additionally, one study34 did not find an association between decompressive craniectomy and GOSE scores 6 months post-trauma. However, it is worth noting that only a few studies have evaluated decompressive craniectomy within a final prediction model of functional outcome.

Length of stay on MVS was a predictor of poorer functional recovery at all follow-up points. A study found similar relationships regarding GOSE scores 6 months after sTBI.8 However, it is worth noting that the average days on MVS in the present study sample were considerably higher than those found in other studies.46–47

Higher education levels were strong predictors of better functional recovery at 3 and 12 months. These findings are in line with previous studies39 where individuals with more favorable sociodemographic conditions had higher survival rates and better functional outcomes. Given that education is a modifiable factor, and considering that approximately 55 % of individuals in our sample have low education, this finding is consistent with previous studies from LMICs, which indicate that individuals with lower educational level are more likely to experience worse functional outcomes after TBI. However, as our data reflect the educational distribution of the broader population, we acknowledge that further population-based studies are needed to determine whether individuals with low education have a higher incidence of TBI compared to other educational strata.48

In the present study, approximately 50 % of individuals with severe TBI demonstrated a positive functional outcome 12 months after the traumatic event. However, it is crucial to emphasize that functional recovery showed a progressive, but not resolving trend, as the prevalence of disabilities and dependence was still considerable. These results align with findings from previous studies,9,19,49–52 which indicate that patients continued to face functional limitations and restrictions in social participation even over a period of 10 years post-traumatic brain injury.

This study has limitations that should be acknowledged. Firstly, the single-center setting may limit the generalizability of the findings to other populations or healthcare settings. Secondly, the lack of data on computed tomography (CT) scans represents a significant limitation, as CT results are strong predictors of outcomes after TBI. Due to the absence of a researcher trained in interpreting these exams, CT data could not be included in our analysis. Additionally, unmeasured covariates, such as whether patients received rehabilitation after hospital discharge, may have influenced the results. This missing information could have provided valuable insights into the functional recovery process. Despite these limitations, this study presents trends in functional recovery after severe TBI in a low- to medium-income country. Most studies on long-term TBI outcomes come from high-income settings; therefore, these findings help trace the functional trajectory from hospital admission to one-year post-injury and may aid in understanding recovery patterns in patients with disadvantaged social conditions in high-risk environments for severe TBI.

Age, high values in the Injury Severity Score, length of stay in mechanical ventilation, the performance of decompressive craniectomy, and level of education were independent variables associated with functional outcome over the first year after severe TBI. The results of the present study demonstrate the influence of clinical and sociodemographic parameters on mortality and functional recovery outcomes after severe TBI. It provides a comprehensive view of the functional trajectory from hospital admission to one year after the traumatic event. The study highlights the need for further research with larger sample sizes, multicenter settings, and longer follow-up periods to track the functional trajectory.

The present study was funded by Fundação de Amparo à Pesquisa (FAPES), Grant ID 09/2020. We acknowledge the study participants and the directors of the Hospital Estadual de Urgência e Emergência for their support.