*Study Limitations and Strengths*

The main limitation of the present study is the small sample size. This limits the conclusions that can be drawn from the data, and the study cannot on its own make definite assumptions on the relationship between neuropsychological screening and long-term functional outcome. Even though all patients were followed by their local outpatient rehabilitation unit, their medical follow-up and rehabilitative efforts varied during the follow-up period. In order to as fully as possible reflect this group of patients, we were restrictive with exclusion criteria; the only one was death or expected death within 3 weeks. This, however, implies that there was less control of medical comorbidities that may have occurred during this time period. The inability to control for further life events, both medical and other, is an inherent flaw in many studies following patients over several years and also greatly restricts the conclusions that can be made from the data.

Initially, over 100 patients were recruited. When considering the incidence of sTBI and the size of the population in Sweden and Iceland, this could in comparative terms be considered a large sample, even though in absolute terms it is small. Given that not all patients could complete a neuropsychological screening and the expected drop-out rate over time, obtaining a larger sample size for a long-term follow-up of sTBI in Sweden is difficult. Drop-out analysis revealed that the only significant difference between included and excluded patients was that included patients had a less severe brain injury according to their GCS score, probably related to the fact that patients able to complete BNIS at 3 months are less severely injured. This highlights another limitation of the study; the results are only generalizable to patients able to complete BNIS at 3 months. The generalizability is also limited to Sweden or countries with a similar social welfare system. An additional weak point is the unusual age difference between the educational groups. However, age was adjusted in the linear regression analysis. A strength of the study is the prospective design; the patients were followed from time of injury until the 5- to 8-year follow-up. We also applied a more nuanced estimate of acute injury severity, using CRASH instead of GCS, thereby better controlling for this variable.

#### **5. Conclusions**

These findings indicate that for patients able to complete screening with BNIS as well as TMT 3 months after sTBI, these screening instruments are valuable tools that help estimate patients' long-term outcome after sTBI. Nevertheless, given the small sample size, the results should be interpreted with caution. The instruments measure different aspects of cognition and seem to relate to different aspects of outcome, thereby complementing each other well. Both are relatively easily administered tests that do not require extensive training to use, but consideration should be given to educational level when interpreting neuropsychological test scores. It would be of value to develop education and age-separated norms for both BNIS and TMT. As executive functions include a broad range of functions, it would also be of interest to further explore the impact of various executive impairments on long-term outcome after sTBI.

**Author Contributions:** Conceptualization, N.E., A.K.G., C.N.D., M.L., B.-M.S., M.S., T.U. and M.C.M.; methodology, N.E., A.K.G., C.N.D., M.L., B.-M.S., M.S., T.U. and M.C.M.; validation, A.K.G., C.N.D. and N.E.; formal analysis, N.E.; investigation, A.K.G., C.N.D., M.L., M.S. and T.U.; resources, A.K.G., C.N.D., M.L., M.S. and T.U.; data curation, A.K.G., C.N.D. and N.E.; writing—original draft preparation, N.E.; writing—review and editing, N.E., A.K.G., C.N.D., M.L., B.-M.S., M.S., T.U. and M.C.M.; visualization, N.E.; supervision, M.C.M., B.-M.S. and M.L.; project administration, A.K.G. and C.N.D.; funding acquisition, N.E., A.K.G., B.-M.S. and M.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Promobilia grant 19111; AFA insurance grants 060833 and 130095; Region Västerbotten; the Swedish Association for Survivors of Polio, Accident, and Injury; and the Swedish Brain Foundation. ALF grants from Uppsala University Hospital, Danderyd Hospital, and Umeå University Hospital.

**Institutional Review Board Statement:** The study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of Stockholm (number 2009/1644/31/3 and 2016/1465-31/4).

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study. The patient gave written informed consent in cases where he or she had the capacity to do so. In the majority of cases, the patient lacked capacity, and the patient's nearest relative gave consent.

**Data Availability Statement:** Data available on request due to restrictions (e.g., privacy or ethical). The data presented in this study are available on request from the corresponding author. The data are not publicly available due to the fact that the ethical board requires the data to be kept confidential in order to protect the privacy of the patients.

**Acknowledgments:** The authors thank the patients and their relatives. The authors also thank Marie Lindgren at the Department of Clinical Rehabilitation Medicine, County Council, Linköping, Sweden, and Richard Levi at the Department of Rehabilitation Medicine, Linköping University, Linköping, Sweden, for their part in realizing the original study. Thanks also to Catharina Apelthun at the Centre for Research and Development, Uppsala University/County Council of Gävleborg, Sweden, for her support and assistance during the statistical analyses. This study is funded by Stiftelsen Promobilia; AFA; Region Västerbotten; the Swedish Association for Survivors of Polio, Accident, and Injury; and the Swedish Brain Foundation.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
