The goal of this observational, prospective cohort study is to learn more about fatigue after burn injury and how it associates with daily activities, health-related quality of life, and return to work. The study is based on data from adult patients who come for follow-up at the Burn Centre's outpatient clinic at Uppsala university hospital 6- and 12 months post-burn.

Patients who come for follow-up are routinely asked to fill out several questionnaires to detect any problems that might have occurred due to the burn injury. Apart from ordinary assessments the study participants were asked to fill out three additional questionnaires. Data from questionnaires together with patient characteristics will be analysed and compiled and presented in a scientific article.

Physical function and daily activities are often affected after a burn injury. Previous research show complications that significantly affect the recovery, such as pain, muscle weakness, scar contractures, hypertrophic scarring, psychosocial problems, and fatigue. The symptoms decrease with time but 26 % still experience fatigue one year post burn and some patients never return to the same level as before the burn injury.

The association between fatigue and different variables has been investigated when it comes to burn patients. Various studies observe a connection between major burns (≥20 % TBSA, the Total Body Surface Area of burnt skin in %) and gender. Associations between fatigue and age, burn depth, and cause of injury show varying/contradictory results. Associations between fatigue and depression have also been observed since the symptoms of fatigue and depression are similar and sometimes overlapping. Edwards et al. show a significant correlation between anxiety/depression and fatigue, and depression one year post burn is reported in 10 - 23 % of the patients.

To increase the knowledge about rehabilitation after burn injury and how fatigue affects daily life post burn the present work aims to investigate to what extent fatigue is a problem among Swedish burn victims. International research is available, but more knowledge is needed to increase the opportunity to help and guide patients towards a more meaningful and manageable daily life.

Objectives Primary objective: to investigate the association between fatigue and

• activity performance,
• health-related quality of life and
• return to work at 6 months, and 12 months post-burn

Secondary objectives:

• To examine whether fatigue is associated with anxiety and depression scores
• To determine if subjective scar assessment is associated with fatigue levels
• To evaluate if intubation during initial treatment is associated with subsequent fatigue

This is a prospective cohort study based on data from patients who suffered a burn injury and were admitted as inpatients to the Burn Centre at Uppsala University Hospital between May 2020 and August 2025. All patients who came for follow-up 6 months after their burn injury were asked to participate, if they fulfilled the inclusion criteria and no exclusion criteria.

Eighty-five patients were enrolled in this study. The number based on a power calculation made in SPSS for Windows, with a desired power of 0.9, a Spearman correlation parameter of 0.4 and a statistical significance level of 0.05. The variance was estimated by the method proposed by Bonett and Wright and the number of patients recommended was 67, at a minimum. All the included patients' have given their written and informed consent.

Outcome definitions The patients are routinely asked to fill out several questionnaires to detect any problems that might have occurred after the burn injury. Apart from ordinary routine assessments the study participants are asked to fill out three additional questionnaires at each follow-up visit. The questionnaires (described in another section) will be handed out to the participants at two time-points, at the 6- and 12-months follow-up visits.

If the patient cannot fill out the questionnaires in connection with the follow-up visit, they may bring them home and return the completed questionnaires in a return envelope as soon as possible after the visit. Should the patient cancel the 12-month follow-up visit they will be contacted by phone and asked if they might consider filling out the questionnaires if they are sent home by mail.

Data analysis Data will be analysed collectively when all the included patients have had their last follow-up at 12 months and all the data have been registered. Data will be analysed using IBM SPSS Statistics for Windows (version 23, IBM Corp, Armonk, NY, USA). The threshold for statistical significance is p<0.05. All confidence intervals presented will be 95%.

Data will be analysed and compared in the following sub-groups:

• Without fatigue, FSS <4, with fatigue, FSS ≥4, with results from each time point.
• %TBSA, minor burns <20% TBSA/major burns ≥20% TBSA. Data will be presented as mean, range, standard deviation, and confidence interval. To assess changes over time, between the two time points, 6- and 12-months post-burn, the results will be analysed using dependent t-test for continuous data, and Wilcoxon signed-rank test for nominal or ordinal data.

A Generalized Linear Mixed Model analysis (GLMM) will be performed to assess the associations between FSS and other variables: EQ VAS, POSAS, HADS anxiety, HADS depression, TBSA %, and PS-ADL.

Patient characteristics such as age, gender, marital status, % total body surface area (%TBSA) burned, length of stay (LOS), surgery, and intubation will be collected from the patients' medical records and presented in a table with demographics, using descriptive statistics; means, range, percentage, and standard deviation, where applicable.

Inclusion Criteria:

1. ≥ 18 years;
2. treated at the Burn unit at least 24 hours and
3. managed Swedish verbally and in writing

Exclusion Criteria:

1. any underlying disease that made it impossible to complete the questionnaires, or
2. the patient chose to abstain the routine 12-month follow-up.

All consecutive patients scheduled for follow-up at the Burn center's outpatient clinic in Uppsala 6 ±3 months post burn were asked to participate in the study.

Should another researcher need access to data from this study to perform another study in the near future, it will be considered, provided that the neccessary permits and ethical approval is obtained.