The association between body mass index and physical function in adult burn survivors: A Burn Model System National Database study

INTRODUCTION

An area of rehabilitation research in burns is the impact of co-morbidities on disease trajectory. Obesity is a comorbidity of increasing public health concern, but its role remains controversial regarding burn injury and physical recovery. Our aim was to evaluate the association between body mass index (BMI) categories as a measure of obesity at discharge and self-reported physical function (PF) during recovery of adult burn survivors.

METHODS

This is a retrospective study on data collected by four major US burn centers, which contribute to the Burn Model System National Database. The data included BMI obtained at hospital discharge and self-reported PF-mobility, using the PROMIS measures assessed at 6, 12, and 24 months after burn. Subjects were classified into weight status categories based on BMI: underweight (BMI <18.5), normal weight (18.5 ≤ BMI <25), overweight (25 ≤ BMI <30), obesity class 1 (30 ≤ BMI <35), obesity class 2 (35 ≤ BMI <40), and obesity class 3 (BMI ≥40). Mixed-effects linear regression models were used to assess the association between BMI categories and PF scores over time, adjusted for patient and injury characteristics.

RESULTS

A total of 496 adult burn patients aged 47 ± 16 years were included, with mean total body surface area (TBSA) burned of 18 ± 19 % and mean BMI at discharge of 28 ± 7 kg/m2. PROMIS PF scores significantly improved over time in the recovery phase after burn (time effect, p < 0.001). Compared to overweight burn patients, normal-underweights exhibited lower PF score by an average of 4.06 units (p = 0.001) but scores increased linearly by an estimated 0.17 units per month (p = 0.01) over the 24 months after discharge. Similarly, compared to overweight burn patients, class 1 obese reported lower PF score by a mean 2.67 units (p = 0.07) but PF increased linearly by 0.15 units per month (p = 0.07) over the 24 months after discharge. These findings were independent of the effects of age at discharge, sex, TBSA burned, and hand and leg burn.

CONCLUSION

Being overweight was associated with improved and faster recovery of PF scores compared to normal, underweight, and obese burn patients during long-term recovery. Hence, our data suggests that long-term recovery and restoration of PF in adult burn survivors is not compromised by a small excess in body weight.

Relationship between body mass index and mortality of burns patients: A systematic review and meta-analysis

This systematic review and meta-analysis aimed to evaluate the relationship between body mass index (BMI) and mortality of burn patients. A comprehensive, systematic search was conducted in different international electronic databases, such as Scopus, PubMed, Web of Science and Persian electronic databases such as Iranmedex, and Scientific Information Database (SID) using keywords extracted from Medical Subject Headings such as "Body mass index", "Burns" and "Mortality" from the earliest to the April 1, 2023. The quality of the studies included in this systematic review was evaluated using the appraisal tool for cross-sectional studies (AXIS tool). Finally, six articles were included in this systematic review and meta-analysis. A total of 16 154 burn patients participated in six studies. Their mean age was 46.32 (SD = 1.99). Of the participants, 71.7% were males. The mean length of hospitalization was 18.80 (SD = 8.08) days, and the average TBSA in burn patients was 38.32 (SD = 2.79) %. Also, the average BMI in burn patients was 27.10 (SD = 1.75). Results found mortality in patients with abnormal BMI (overweight to morbidity BMI) was 0.19 more than normal BMI (ES: 1.19, 95%CI: 0.76-1.87, Z = 0.75, I2 : 71.8%, p = 0.45). Results of linear dose-response showed each 5 kg/m2 increase in BMI was associated with a 5% increase in mortality that was marginally significant (ES: 1.05, 95%CI: 1.00-1.11, Z = 1.99, I2 : 22.2%, p = 0.047). There was a non-linear relationship between levels of BMI and mortality (Prob > χ2  = 0.02). There was an increase in mortality from percentile 10 to 50, although it was not significant (Correlational coefficient: 0.01, p = 0.85). Also, there was an increase in mortality rate from percentile 50 to 90 that was statistically significant (correlational coefficient: 0.06, p = 0.047). Finally, the results of the study indicated BMI can increase the chance of mortality by 0.19, although it was not significant. As a result, more studies are needed to better judge the relationship between BMI and mortality in burn victims.

Baseline glucose levels moderate the association between burn-related mortality inpatients with obesity

BACKGROUND

Differing findings concerning outcomes for burn patients with obesity indicate additional factors at play. One possible explanation could lie in determining metabolically healthy versus unhealthy obesity, which necessitates further study.

METHODS

A retrospective study was conducted using the Cerner Health Facts® Database. Deidentified patient data from 2014 to 2018 with second or third-degree burn injuries were retrieved. A moderator analysis was conducted to determine if the association between increased body mass index (BMI) and mortality is moderated by baseline glucose level, a surrogate marker associated with metabolically unhealthy obesity.

RESULTS

The study included 4682 adult burn patients. BMI alone was not associated with higher mortality (β = 0.106, p = 0.331). Moderation analysis revealed that baseline glucose level significantly modulated the impact of BMI on burn-related obesity; patients with higher BMI and higher baseline blood glucose levels had higher mortality than those with lower baseline blood glucose levels (β = 0.277, p = 0.009). These results remained unchanged after adjusting for additional covariates (β = 0.285, p = 0.025) and inthe sensitivity analysis.

CONCLUSIONS

Increased baseline glucose levels indicate increased mortality in obese patients with burn injuries, emphasizing the differentiation between metabolically unhealthy versus healthy obesity.

Associations between body mass index and all-cause mortality: A systematic review and meta-analysis

Fasting insulin and c-reactive protein confound the association between mortality and body mass index. An increase in fat mass may mediate the associations between hyperinsulinemia, hyperinflammation, and mortality. The objective of this study was to describe the "average" associations between body mass index and the risk of mortality and to explore how adjusting for fasting insulin and markers of inflammation might modify the association of BMI with mortality. MEDLINE and EMBASE were searched for studies published in 2020. Studies with adult participants where BMI and vital status was assessed were included. BMI was required to be categorized into groups or parametrized as non-first order polynomials or splines. All-cause mortality was regressed against mean BMI squared within seven broad clinical populations. Study was modeled as a random intercept. β coefficients and 95% confidence intervals are reported along with estimates of mortality risk by BMIs of 20, 30, and 40 kg/m2 . Bubble plots with regression lines are drawn, showing the associations between mortality and BMI. Splines results were summarized. There were 154 included studies with 6,685,979 participants. Only five (3.2%) studies adjusted for a marker of inflammation, and no studies adjusted for fasting insulin. There were significant associations between higher BMIs and lower mortality risk in cardiovascular (unadjusted β -0.829 [95% CI -1.313, -0.345] and adjusted β -0.746 [95% CI -1.471, -0.021]), Covid-19 (unadjusted β -0.333 [95% CI -0.650, -0.015]), critically ill (adjusted β -0.550 [95% CI -1.091, -0.010]), and surgical (unadjusted β -0.415 [95% CI -0.824, -0.006]) populations. The associations for general, cancer, and non-communicable disease populations were not significant. Heterogeneity was very large (I2  ≥ 97%). The role of obesity as a driver of excess mortality should be critically re-examined, in parallel with increased efforts to determine the harms of hyperinsulinemia and chronic inflammation.

Examining Obesity and Its Association With Burn Injury: A Secondary Analysis of the Transfusion Requirement in Burn Care Evaluation Study

INTRODUCTION

Literature examining the connection between obesity and burn injuries is limited. This study is a secondary analysis of a multicenter trial data set to investigate the association between burn outcomes and obesity following severe burn injury.

MATERIALS AND METHODS

Body mass index (BMI) was used to stratify patients as normal weight (NW; BMI 18.5-25), all obese (AO; any BMI>30), obese I (OI; BMI 30-34.9), obese II (OII; BMI 35-39.9), or obese III (OIII; BMI>40). The primary outcome examined was mortality. Secondary outcomes included hospital length of stay (LOS), number of transfusions, injury scores, infection occurrences, number of operations, ventilator days, intensive care unit LOS, and days to wound healing.

RESULTS

Of 335 patients included for study, 130 were obese. Median total body surface area (TBSA) was 31%, 77 patients (23%) had inhalation injury and 41 patients died. Inhalation injury was higher in OIII than NW (42.1% versus 20%, P = 0.03). Blood stream infections (BSI) were higher in OI versus NW (0.72 versus 0.33, P = 0.03). Total operations, ventilator days, days to wound healing, multiorgan dysfunction score, Acute Physiology and Chronic Health Evaluationscore, hospital LOS, and intensive care unit LOS were not significantly affected by BMI classification. Mortality was not significantly different between obesity groups. Kaplan-Meier survival curves did not significantly differ between the groups (χ2 = 0.025, P = 0.87). Multiple logistic regression identified age, TBSA, and full thickness burn as significant independent predictors (P < 0.05) of mortality; however, BMI classification itself was not predictive of mortality.

CONCLUSIONS

No significant association between obesity and mortality was seen after burn injury. Age, TBSA, and percent full- thickness burn were independent predictors of mortality after burn injury, while BMI classification was not.

Impact of elevated body mass index on burn injury-associated mortality in a representative US sample

BACKGROUND

The impact of obesity on burn-related mortality is inconsistent and incongruent; despite being a risk factor for numerous comorbidities that would be expected to increase complications and worsen outcomes, there is evidence of a survival advantage for patients with high body mass index-the so-called obesity paradox. We used a national data set to explore further the relationship between body mass index and burn-related mortality.

METHODS

Deidentified data from patients with second and third-degree burns between 2014 and 2018 were obtained from the Cerner Health Facts Database. Univariate and multivariate regression models were created to identify potential factors related to burn-related mortality. A restricted cubic spline model was built to assess the nonlinear association between body mass index and burn-related mortality. All statistical analyses were conducted using R (R Foundation for Statistical Computing).

RESULTS

The study included 9,405 adult burn patients. Univariate and multivariate analyses revealed that age (odds ratio = 2.189 [1.771, 2.706], P < .001), total burn surface area (odds ratio = 1.824 [1.605, 2.074], P < .001), full-thickness burns (odds ratio = 1.992 [1.322, 3.001], P < .001), and comorbidities (odds ratio = 2.03 [1.367, 3.014], P < .001) were associated with increased mortality. Sensitivity analysis showed similar results. However, a restricted cubic spline indicated a U-shaped relation between body mass index and burn-related mortality. The nadir of body mass index was 28.92 kg/m², with the lowest mortality. This association persisted even after controlling for age, total burn surface area, full-thickness burns, and comorbidities, which all remained significant.

CONCLUSION

This study confirms a U-shaped association between body mass index and burn-related mortality along with age, total burn surface area, full-thickness burns, and comorbidities as risk factors.

Strength of association between body mass index and physical function scores in paediatric burn patients: A National Institute on Disability, Independent Living, and Rehabilitation Research Burn Model System study

OBJECTIVE

Increased body weight has been associated with reduced muscle wasting in the early catabolic phase after a severe burn. Yet, overweight and obese non-burn children often exhibit impaired musculoskeletal function, which may lead to poor physical function (PF). We aimed to determine the association between body mass index (BMI) at discharge and self-reported PF and caregiver proxy-reported PF during recovery of burned children.

MATERIALS AND METHODS

This is a retrospective multisite longitudinal study in paediatric burn patients ((8-17 y old at time of burn). PF outcome measures were self-reported mobility, proxy-reported mobility, and upper extremity PF evaluated using PROMIS measures at 6-, 12-, and 24-months after injury. Primary exposure variable was BMI-for-age at discharge.

RESULTS

A total of 118 paediatric patients, aged 11.7 ± 3.3 y, with burns covering 37.6 ± 18.8% of their total body surface area (TBSA) and BMI-for-age of 23.1 ± 5.4 kg/m² at discharge were analyzed. BMI at discharge was not significantly associated with self-reported mobility scores 6 months after burn (beta coefficient =-0.23, p = 0.31), had a positive effect on mobility at 12 months (beta = 0.46, p = 0.05), and no effect at 24 months after injury (beta=-0.10, p = 0.60), when adjusted for burn size. BMI did not have a significant effect on proxy-reported mobility or upper extremity PF.

CONCLUSION

A greater BMI at discharge was associated with improved self-reported PF at 12 months after burn but not at 6 months or 24 months, which suggests a faster recovery of PF in paediatric patients of larger body weight. Our data suggests that a larger body weight does not compromise the recovery of PF after burn.

Differences by age in the obesity paradox in severe burns

BACKGROUND

Many studies show a "obesity paradox", which seems to protect against death. Whether an obesity paradox space is present in severe burn patients remains a matter of great debate. Most research on the obesity paradox of burn injuries is classified by body mass index (BMI) rather than by age.

OBJECTIVE

To investigate whether the obesity paradox exists in severe burn patients stratified by age.

METHODS

Retrospective analysis was performed on 490 patients with severe burns who were ≥ 18 years of age and were admitted to Fujian Medical University Union Hospital from January 2005 to December 2020. Demographic and clinical characteristics were collected, including age, BMI, total body surface area (TBSA), presence of inhalation injury, abbreviated burn severity index (ABSI) score, diabetes comorbidities, hypertension comorbidities, and in-hospital mortality. The patients were divided into the younger group (18 ≤ age<65 years) and the older group (age ≥ 65 years). The important variables of the two groups were compared. The predictive value of BMI stratified by age on in-hospital mortality was evaluated by binary logistic regression analysis and the Cochran's and Mantel-Haenszel statistics.

RESULTS

A total of 490 patients were selected for this study, and were divided into the younger group (413) and the elderly group (77) according to their ages. In the younger group, logistic regression analyses indicated that high BMI remained significantly and independently associated with decreased in-hospital mortality (P = 0.021). That is, in-hospital mortality decreased by 17.8% when BMI increased by 1 kg/m². In the older group, BMI was not associated with in-hospital mortality (P = 0.808). In the younger group, the results of Pearson's chi-square test was less than 0.05, indicating a correlation between BMI and prognosis. In the older group, the conclusion was contrary with, no correlation between BMI and prognosis. If the confounding factors of age were not considered, this results in no correlation between BMI and prognosis. In the younger group, the survival/death ratio of patients with overweight and obesity was 2.078 times that of patients with normal weight.

CONCLUSION

In this study of patients with severe burns, overweight and obesity had protective effect on burn injury in the younger group (18 ≤ age<65 years), but not in the older group (age ≥ 65 years). Investigating the obesity paradox in burn patients needs to consider age differences. However, multicentre clinical trials are needed to verify the results.

Systemic Complications of Obesity in Operative Acetabular Fractures

OBJECTIVE

To determine the effect of obesity on rates of systemic complications in operatively treated acetabular fractures.

DESIGN

Retrospective Case-Control study.

SETTING

Level 1 Trauma Center.

PATIENTS/PARTICIPANTS

All patients with acetabular fractures managed operatively from January 2015 to December 2019. Patients were divided into groups based on their body mass index (BMI) (normal weight = BMI <25 kg/m2, overweight = BMI 25-30, obese = BMI 30-40, and morbidly obese = BMI >40).

INTERVENTION

Operative management of an acetabular fracture.

MAIN OUTCOME MEASUREMENT

Systemic complications, including mortality, sepsis, pneumonia, acute respiratory distress syndrome, deep vein thrombosis, pulmonary embolism, or venous thrombotic event.

RESULTS

A total of 428 patients were identified. One hundred nine patients (25.4%) were in normal weight, 133 (31.1%) were overweight, 133 (31.1%) were obese, and 53 (12.4%) were morbidly obese. The rate of systemic complications was 17.5%, and overall mortality rate was 0.005%. There were no significant differences between the different BMI groups in all-cause complications or any individual complications. When the morbidly obese group was compared with all other patients, there were also no significant differences in all-cause complications or any individual complications.

CONCLUSION

In conclusion, in this study, there was no association with increasing BMI and inpatient systemic complications after operative management of acetabular fractures. As we continue to refine our understanding of how obesity affects outcomes after acetabular fracture surgery, other indices of obesity might prove more useful in predicting complications. In the obese population, there are well-documented risks of postoperative infections and challenges in obtaining an anatomic reduction, but the fear of postoperative systemic complications should not deter surgeons from undertaking operative management of acetabular fractures in the obese population. Because the prevalence of obesity in trauma patients continues to increase, it is incumbent on us to continue to improve our understanding of optimal treatment for our patients.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Burn Outcomes at Extremes of Body Mass Index- Underweight is as problematic as Morbid Obesity

Limited evidence suggests that obesity adversely affects burn outcomes. However, the impacts of body mass index (BMI) across the continuum has not been fully characterized. Therefore, we aimed to characterize outcomes after burn injury across the BMI continuum. We hypothesized that 'normal' BMI (18.5-24.9) would have the lowest mortality and complication rates. The US National Trauma Data Bank (NTDB) was queried for adult burn-injured patients from 2007-2015. Admission BMI was calculated and grouped according to World Health Organization (WHO) classification. The primary outcome was in-hospital mortality. Secondary outcomes of time to wound closure, length of stay (LOS), and inpatient complications were similarly assessed. Of the 116,008 burn patient encounters that were identified, 7,243 underwent at least one operation for wound closure. Mortality was lowest in the overweight (p=0.039) and obese I cohorts (BMI 25-29.9, 30.0-34.9) at 2.9% and increased in both directions of the BMI continuum to 4.1% in the underweight (p=0.032) and 5.1% in the morbidly obese (class III) group (p=0.042). Time to final wound closure was longest in the two BMI extremes. BMI >40 was associated with increased ICU days, ventilator days, renal and cardiac complications. BMI <18.5 had increased hospital days and rates of sepsis. Aberrations in metabolism associated with both increases and decreases of body weight may cause pathophysiologic changes that lead to worsened outcomes in burn-injured patients. In addition to morbidly obese patients, underweight patients also experience increased burn-related death and complications. In contrast, overweight BMI patients may have greater physiologic reserves without the burden of obesity or sarcopenia.

Association of Body Mass Index on Injuries and Outcomes After Ground-Level Falls

BACKGROUND

The impact of body mass index (BMI) on trauma severity after ground-level falls (GLF) is currently unclear. This study aimed to examine the associations between BMI, injuries, and outcomes after GLF.

STUDY DESIGN

All patients ≥16 years of age injured by GLF were queried from the TQIP database (2013-2017). Exclusions were transfers, emergency department death, AIS 6 in any region, and missing data. Body mass index defined study groups: Underweight (BMI<18.5), Normal (BMI 18.5-24.9), Overweight (25.0-29.9), and Obese (≥30).

RESULTS

After exclusions, 131 570 patients remained for analysis. Most patients had a normal BMI (n = 58 503, 44%). Median ISS was 9 [IQR 9-10] in all groups. The Obese group had significantly lower rates of fractures than the Normal group, particularly femur fractures (53% vs. 64%, P < .001), but required orthopedic surgical intervention more frequently (45% vs. 41%, P < .001). On multivariate analysis, being overweight was protective against mortality (OR .881, P = .005), while obesity was not associated with mortality (OR 1.012, P = .821).

CONCLUSION

Increasing BMI may be protective against both fracture risk and mortality after GLF. However, obese patients require operative fixation more frequently. Particularly as fracture diagnosis may be more challenging in the obese, special care should be taken during their tertiary surveys after GLF to ensure injuries are not missed.