BMI and risk of serious upper body injury following motor vehicle crashes: concordance of real-world and computer-simulated observations

Assessing Factors Associated with Non-Fatal Injuries from Road Traffic Accidents among Malaysian Adults: A Cross-Sectional Analysis of the PURE Malaysia Study

Non-fatal injuries (NFIs) due to road traffic accidents (RTAs) are a public health problem worldwide that significantly impacts the population morbidity and healthcare costs. As the demands for vehicles in developing countries, such as Malaysia, is increasing annually, the present study aims to determine the prevalence and factors associated with NFIs due to RTAs among Malaysia’s adult population. Methods: This was a cross-sectional study involving 15,321 participants from the Prospective Urban and Rural Epidemiological (PURE) study conducted in Malaysia. Participants reported whether they had experienced an NFI that limited their normal activities within the past 12 months. Data on risk factors for NFIs were elicited. Multiple logistic regression models were fitted to identify the associated factors. Results: Overall, 863 participants (5.6% of 15,321) reported at least 1 NFI in the past 12 months, with 303 caused by RTAs (35.1%), 270 caused by falls (31.3%) and 290 attributed to other causes (33.6%). The factors associated with higher odds of sustaining an NFI due to an RTA were being male (adjusted odd ratio (AOR) 2.08; 95% CI 1.33–3.26), having a primary (2.52; 1.40–4.55) or secondary (2.64; 1.55–4.49) level of education, being overweight to obese (1.40; 1.01–1.94), being currently employed (2.03; 1.31–3.13) and not practicing a noon nap/siesta (1.38; 1.01–1.89). Conclusions: The occurrence of NFIs due to RTAs is highly preventable with strategic planning aimed at reducing the risk of RTAs among the Malaysian population. Interventions focusing on protecting road users, especially those who drive two-wheelers, with proactive road safety awareness and literacy campaigns, combined with strict enforcement of the existing traffic laws and behavioural modifications, may reduce the risk of NFIs following RTAs.

Influence of a Passenger Position Seating on Recline Seat on a Head Injury during a Frontal Crash

Presently, most passive safety tests are performed with a precisely specified seat position and carefully seated ATD (anthropomorphic test device) dummies. Facing the development of autonomous vehicles, as well as the need for safety verification during crashes with various seat positions such research is even more urgently needed. Apart from the numerical environment, the existing testing equipment is not validated to perform such an investigation. For example, ATDs are not validated for nonstandard seatback positions, and the most accurate method of such research is volunteer tests. The study presented here was performed on a sled test rig utilizing a 50cc Hybrid III dummy according to a full factorial experiment. In addition, input factors were selected in order to verify a safe test condition for surrogate testing. The measured value was head acceleration, which was used for calculation of a head injury criterion. What was found was an optimal seat angle −117°—at which the head injury criteria had the lowest represented value. Moreover, preliminary body dynamics showed a danger of whiplash occurrence for occupants in a fully-reclined seat.

Assessing the Cushion Effect: A Systematic Review and Meta-Analysis of the Role of Obesity in Motor Vehicle Injuries and Fatalities

PURPOSE

A systematic review and meta-analysis were done to evaluate the effect of obesity in injury and mortality due to motor vehicle accidents.

MATERIALS & METHODS

The systematic review consisted of 20 studies meeting the inclusion criteria. The meta-analysis was conducted on these studies to analyze obesity as a risk factor for specific injuries, as well as overall injury and mortality compared to non-obese patients.

RESULTS

The data revealed that obesity was associated with increased lower extremity injuries (odds ratio [OR] = 1.44, 95% confidence interval [CI] = 1.19-1.69, P ≤ 0.05), neck injuries (OR = 3.38, 95% CI = 1.58-5.19, P ≤ 0.05), and overall mortality (OR = 1.51, 95% CI = 1.40-1.61, P ≤ 0.05). When stratified for obesity class with class I as BMI >30.1-34.9, class II BMI 35-39.9, and class III BMI >40, only class II (OR = 1.20, 95% CI = 1.15-1.24, P ≤ 0.05) and class III (OR = 1.49, 95% CI = 1.30-1.68, P ≤ 0.05) were associated with increased mortality risk. No significant differences were seen with head, upper extremity, thoracic, abdominal, or pelvic injuries.

CONCLUSION

Obesity is a risk factor in motor vehicle accidents for fatality and injury, specifically lower extremity and neck injuries.

Restraint systems considering occupant diversity and pre-crash posture

OBJECTIVE

Use volunteer data and parametric finite element (FE) human body models to investigate how restraint systems can be designed to adapt to a diverse population and pre-crash posture changes induced by active safety features.

METHODS

Four FE human models were generated by morphing the midsize male GHBMC simplified model into geometries representing a midsize male, midsize female, short obese female (BMI 40 kg/m²), and large obese male (BMI 40 kg/m²) based on statistical skeleton and body shape geometry models. Each human model was positioned in a generic vehicle driver environment using two occupant pre-crash postures based on volunteer test results including one resulting from 1-g abrupt braking events. Improved restraint designs were manually developed for each occupant model in a 56 km/h frontal crash condition by adding a knee airbag, adjusting the shoulder belt load limit, steering column force, and driver airbag properties (tethers, inflation, and vent size). The improved designs were then tested at both pre-crash postures. Injury risks for the head, neck, chest, and lower extremities were analyzed.

RESULTS

Human size and shape dominated the occupant injury measures, while the pre-crash-braking induced posture had minimal effects. Some of the safety concerns observed for large occupants include head strike-through the airbag and a conflict between head and chest injuries, which were mitigated by a stiffer restraint system with properly-tuned driver airbag. Chest injuries were a prominent safety concern for female occupants, mitigated by a softer seatbelt and smaller airbag size near the chest. Obese occupants exhibited a higher likelihood of lower extremity injuries indicating a need for a knee airbag. A diverse set of improved restraint designs were effective in lowering injury risks, indicating that restraint adaptability is necessary for accounting for occupant diversity.

CONCLUSIONS

This study investigated the effects of occupant size and shape variability, posture, and restraint design on injury risk for high-speed frontal crashes. More forward initial postures due to active safety features may decrease head, neck, and lower extremity injury risk, but may also increase chest injury risk. Safety concerns observed for large occupants include head strike-through and a conflict between head and chest injuries. Obese occupants had higher knee-thigh-hip injury risk. New restraints that adapt to occupant size and body shape may improve crash safety for all occupants. Further investigation is needed to confirm and extend the findings of this study.

Frontal crash simulations using parametric human models representing a diverse population

Objective: Analyses of crash data have shown that older, obese, and/or female occupants have a higher risk of injury in frontal crashes compared to the rest of the population. The objective of this study was to use parametric finite element (FE) human models to assess the increased injury risks and identify safety concerns for these vulnerable populations. Methods: We sampled 100 occupants based on age, sex, stature, and body mass index (BMI) to span a wide range of the U.S. adult population. The target anatomical geometry for each of the 100 models was predicted by the statistical geometry models for the rib cage, pelvis, femur, tibia, and external body surface developed previously. A regional landmark-based mesh morphing method was used to morph the Global Human Body Models Consortium (GHBMC) M50-OS model into the target geometries. The morphed human models were then positioned in a validated generic vehicle driver compartment model using a statistical driving posture model. Frontal crash simulations based on U.S. New Car Assessment Program (U.S. NCAP) were conducted. Body region injury risks were calculated based on the risk curves used in the US NCAP, except that scaling was used for the neck, chest, and knee-thigh-hip injury risk curves based on the sizes of the bony structures in the corresponding body regions. Age effects were also considered for predicting chest injury risk. Results: The simulations demonstrated that driver stature and body shape affect occupant interactions with the restraints and consequently affect occupant kinematics and injury risks in severe frontal crashes. U-shaped relations between occupant stature/weight and head injury risk were observed. Chest injury risk was strongly affected by age and sex, with older female occupants having the highest risk. A strong correlation was also observed between BMI and knee-thigh-hip injury risk, whereas none of the occupant parameters meaningfully affected neck injury risks. Conclusions: This study is the first to use a large set of diverse FE human models to investigate the combined effects of age, sex, stature, and BMI on injury risks in frontal crashes. The study demonstrated that parametric human models can effectively predict the injury trends for the population and may now be used to optimize restraint systems for people who are not similar in size and shape to the available anthropomorphic test devices (ATDs). New restraints that adapt to occupant age, sex, stature, and body shape may improve crash safety for all occupants.

The impact of body mass index on severity of cervical spine fracture: A retrospective cohort study

Background:

No study has evaluated the relationship between increasing BMI and severity/type of cervical spine injuries.

Aims and Objectives:

The objective of our study was to study the impact of body mass index (BMI) on severity of cervical spine fracture.

Methods:

We performed a retrospective cohort study of patients with traumatic cervical spine fractures at a level I trauma center over a 74-year period. CT scans of the cervical spine were blindly graded according to the AO Spine sub-axial cervical spine classification. The association between BMI and severity of cervical spine fracture was studied by multiple-variable logistic regression.

Results:

A total of 291 patients with an average BMI of 26.1 ± 5.4 kg/m² were studied. Higher BMI was not associated with more severe injury (OR 1.03, 95%, CI: 0.97–1.08). For rollover motor vehicle accident (MVA), the association was trending towards significance (OR 2.55, 95%, CI: 0.98-6.66, P = 0.06).

Conclusions:

Patients with higher BMI may be predisposed to more severe cervical spine fracture in rollover MVA, but not non-rollover MVA or falls.

Prevalence of cardiometabolic risk factors among professional male long-distance bus drivers in Lagos, south-west Nigeria: a cross-sectional study

Background

Professional drivers are known to be at high risk of cardiovascular disease (CVD). This study was carried out to highlight these risk factors and their predictors among male long–distance professional bus drivers in Lagos, southwest Nigeria, with a view to improving health awareness in this group.

Methods

Socio–demographic data, anthropometric indices, blood pressure, fasting plasma blood glucose levels and lipid and physical activity profiles of 293 drivers were measured.

Results

Mean age of the study population was 48 ± 9.7 years; 71.0 and 19.5% of the drivers used alcohol and were smokers, respectively; and 50.9% were physically inactive. The prevalence of overweight and obesity was 41.7 and 21.1%, respectively, while 39.7 and 13.9% were hypertensive and diabetic, respectively. Ninety (31.3%) subjects had impaired fasting glucose levels while 56.3% had dyslipidaemia. Predictors of hypertension were age and body mass index (BMI). BMI only was a predictor of abnormal glucose profile.

Conclusion

Professional male long–distance bus drivers in this study showed a high prevalence of a cluster of risk factors for CVD.

Development and validation of a generic finite element vehicle buck model for the analysis of driver rib fractures in real life nearside oblique frontal crashes

OBJECTIVE

Frontal crashes still account for approximately half of all fatalities in passenger cars, despite several decades of crash-related research. For serious injuries in this crash mode, several authors have listed the thorax as the most important. Computer simulation provides an effective tool to study crashes and evaluate injury mechanisms, and using stochastic input data, whole populations of crashes can be studied. The aim of this study was to develop a generic buck model and to validate this model on a population of real-life frontal crashes in terms of the risk of rib fracture.

METHOD

The study was conducted in four phases. In the first phase, real-life validation data were derived by analyzing NASS/CDS data to find the relationship between injury risk and crash parameters. In addition, available statistical distributions for the parameters were collected. In the second phase, a generic parameterized finite element (FE) model of a vehicle interior was developed based on laser scans from the A2MAC1 database. In the third phase, model parameters that could not be found in the literature were estimated using reverse engineering based on NCAP tests. Finally, in the fourth phase, the stochastic FE model was used to simulate a population of real-life crashes, and the result was compared to the validation data from phase one.

RESULTS

The stochastic FE simulation model overestimates the risk of rib fracture, more for young occupants and less for senior occupants. However, if the effect of underestimation of rib fractures in the NASS/CDS material is accounted for using statistical simulations, the risk of rib fracture based on the stochastic FE model matches the risk based on the NASS/CDS data for senior occupants.

CONCLUSION

The current version of the stochastic model can be used to evaluate new safety measures using a population of frontal crashes for senior occupants.

Body Morphology and Its Associations With Thoracolumbar Trauma Sustained in Motor Vehicle Collisions

OBJECTIVE

This study investigates the relationship between body mass index (BMI) and the patterns of thoracolumbar spinal fractures sustained by patients in motor vehicle collisions (MVCs).

DESIGN

The Crash Injury Research and Engineering Network (CIREN) database was used to analyze prospective data on patients involved in MVCs of moderate severity.

METHODS

Thoracolumbar fractures in 631 subjects were analyzed for patient-, vehicle-, and crash-related factors. Spine injuries were classified according to a modified Denis classification system. Subjects were stratified into BMI subgroups that were then analyzed by injury level, fracture pattern, associated systemic injury, and mortality.

RESULTS

Obesity (BMI ≥ 30.0) was found to be associated with a more cephalad level of injury. Mean BMI was higher in 67 patients with fatal outcomes compared with 557 survivors. Patients who sustained a thoracolumbar fracture and another system injury were more likely to be overweight and obese. Among the various fracture patterns analyzed, BMI was highest in patients with extension injuries.

CONCLUSION

This study characterizes the relationship between body morphology and the thoracolumbar injury patterns associated with MVC to improve understanding of the overall morbidity and mortality of these injuries. These results corroborate research demonstrating the unique relationships between patients who are obese and specific patterns of injury and higher injury severity caused by MVCs and establish a rationale for specifically including thoracolumbar spine parameters in crash safety standards.

U-shaped association of body mass index in early adulthood with unintentional mortality from injuries: a cohort study of Swedish men with 35 years of follow-up

OBJECTIVES

To investigate the dose-response association between body mass index (BMI) in young adulthood and the risk of mortality caused by unintentional injuries.

METHODS

We performed a cohort study including 7 43 398 men identified by linkage of the Multigeneration Register and the Military Service Conscription Register. Cox regression models were used to examine crude and adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) of the relationships between BMI at age 18-20 years and the risk of death from all unintentional injuries as well as from specific unintentional injuries. We then estimated the population attributable fractions (PAFs)-the proportion of unintentional deaths that was attributable to underweight, overweight and obesity in this population-based cohort.

RESULTS

During 35.9 years of follow-up, 6461 deaths occurred from unintentional injuries, including 3064 deaths from road injury, 978 from poisoning, 503 from falls, 243 from fire and 348 from drowning. Underweight subjects had a higher risk of mortality in all unintentional injuries (HR, 1.05; 95% CI, 1.03-1.10) and mortality in burns (HR, 1.65; 95% CI, 1.13-2.40) compared with BMI between 18.5 and 22.5 kg m(-2) (reference group). BMI >25 kg m(-2) was associated with increased risk of death from all unintentional injuries (HR, 1.36; 95% CI, 1.12-1.65) and road accidents (HR, 1.50; 95% CI, 1.14-1.97). Estimates of PAF suggested that 4.4% of the mortality in Swedish men caused by unintentional injuries could have been avoided if BMI values were kept between 18.5 and 22.5 kg m(-2).

CONCLUSIONS

A U-shaped association was observed between BMI and risk of unintentional death. Both underweight and overweight were associated with increased mortality risk for all unintentional injuries and for subtype causes. Our study suggests that BMI might be a significant target for preventive interventions on deaths caused by unintentional injuries.

Seat belt use and fit among drivers aged 75 years and older in their own vehicles

OBJECTIVE

This article aims to describe seat belt wearing patterns and quality of seat belt fit among drivers aged 75 years and older. A secondary aim is to explore associations between body shape, comfort, and seat belt use patterns.

METHODS

This is an observation and survey study of a cohort of 380 drivers aged 75 years and over. During home visits, photographs were taken of the drivers in their vehicles for later analysis of belt fit and a short survey was also administered to collect demographic data and information about seat belt use and comfort. Seat belt fit and use of belt and seat accessories were analyzed from the photographs.

RESULTS

Data from 367 participants with photographs were analyzed. Whereas 97% reported using a seat belt and 90% reported their seat belt to be comfortable, 21% reported repositioning their seat belt to improve comfort. Good sash and lap belt fit were achieved in 53 and 59% of participants, respectively, but only 35% achieved overall good fit. Both poor sash and lap belt fit were observed in 23% of participants. Drivers who were in the obese category had over twice the odds (95% confidence interval [CI], 1.2-4.1) of having a poor lap belt fit than those in the normal body mass index [BMI] range, and drivers who were overweight had 1.8 times the odds (95% CI, 1.1-2.9) of having poor lap belt fit. Older females also had twice the odds (95% CI, 1.3-3.5) of poor lap belt fit compared to older males, regardless of BMI. Sash belt fit did not vary significantly by BMI, stature, or gender. However older drivers who reported that they had not made any adjustments to the D-ring height had 1.7 times the odds of having poor sash belt fit than those who made adjustments (1.2-2.9). Females were 7.3 times more likely to report comfort problems than males (95% CI, 3.2, 16.3) but there was no association between reported comfort and BMI or seat belt fit. Drivers who reported comfort problems had 6 times the odds (3.2-13.6) of also reporting active repositioning of the belt.

CONCLUSIONS

The results suggest that older drivers face challenges in achieving comfortable and correct seat belt fit. This may have a negative impact on crash protection. Belt fit problems appear to be associated with body shape, particularly high BMI and gender. There is a need for further investigation of comfort accessories; in the interim, older drivers and occupants should be encouraged to use features such as D-ring adjusters to improve sash belt fit.

Effect of weight, height and BMI on injury outcome in side impact crashes without airbag deployment

A comprehensive analysis is performed to evaluate the effect of weight, height and body mass index (BMI) of occupants on side impact injuries at different body regions. The accident dataset for this study is based on the National Automotive Sampling System-Crashworthiness Data System (NASS-CDS) for accident year 2000-08. The mean BMI values for driver and front passenger are estimated from all types of crashes using NASS database, which clearly indicates that mean BMI has been increasing over the years in the USA. To study the effect of BMI in side impact injuries, BMI was split into three groups namely (1) thin (BMI<21), (2) normal (BMI 24-27), (3) obese (BMI>30). For more clear identification of the effect of BMI in side impact injuries, a minimum gap of three BMI is set in between each adjacent BMI groups. Car model years from MY1995-1999 to MY2000-2008 are chosen in order to identify the degree of influence of older and newer generation of cars in side impact injuries. Impact locations particularly side-front (F), side-center (P) and side-distributed (Y) are chosen for this analysis. Direction of force (DOF) considered for both near side and far side occupants are 8 o'clock, 9 o'clock, 10 o'clock and 2 o'clock, 3 o'clock and 4 o'clock respectively. Age <60 years is also one of the constraints imposed on data selection to minimize the effect of bone strength on the occurrence of occupant injuries. AIS2+ and AIS3+ injury risk in all body regions have been plotted for the selected three BMI groups of occupant, delta-V 0-60kmph, two sets (old and new) of car model years. The analysis is carried with three approaches: (a) injury risk percentage based on simple graphical method with respect to a single variable, (b) injury distribution method where the injuries are marked on the respective anatomical locations and (c) logistic regression, a statistical method, considers all the related variables together. Lower extremity injury risk appears to be high for thin BMI group. It is found that BMI does not have much influence on head injuries but it is influenced more by the height of the occupant. Results of logistic analysis suggest that BMI, height and weight may have significant contribution towards side impact injuries across different body regions.

Comparing the effects of age, BMI and gender on severe injury (AIS 3+) in motor-vehicle crashes

BACKGROUND

The effects of age, body mass index (BMI) and gender on motor vehicle crash (MVC) injuries are not well understood and current prevention efforts do not effectively address variability in occupant characteristics.

OBJECTIVES

(1) Characterize the effects of age, BMI and gender on serious-to-fatal MVC injury. (2) Identify the crash modes and body regions where the effects of occupant characteristics on the numbers of occupants with injury is largest, and thereby aid in prioritizing the need for human surrogates that represent different types of occupant characteristics and adaptive restraint systems that consider these characteristics.

METHODS

Multivariate logistic regression was used to model the effects of occupant characteristics (age, BMI, gender), vehicle and crash characteristics on serious-to-fatal injuries (AIS 3+) by body region and crash mode using the 2000-2010 National Automotive Sampling System (NASS-CDS) dataset. Logistic regression models were applied to weighted crash data to estimate the change in the number of annual injured occupants with AIS 3+ injury that would occur if occupant characteristics were limited to their 5th percentiles (age≤17 years old, BMI≤19kg/m(2)) or male gender.

RESULTS

Limiting age was associated with a decrease in the total number of occupants with head [8396, 95% CI 6871-9070] and thorax injuries [17,961, 95% CI 15,960-18,859] across all crash modes, decreased occupants with spine [3843, 95% CI 3065-4242] and upper extremity [3578, 95% CI 1402-4439] injuries in frontal and rollover crashes and decreased abdominal [1368, 95% CI 1062-1417] and lower extremity [4584, 95% CI 4012-4995] injuries in frontal impacts. The age effect was modulated by gender with older females more likely to have thorax and upper extremity injuries than older males. Limiting BMI was associated with 2069 [95% CI 1107-2775] fewer thorax injuries in nearside crashes, and 5304 [95% CI 4279-5688] fewer lower extremity injuries in frontal crashes. Setting gender to male resulted in fewer occupants with head injuries in farside crashes [1999, 95% CI 844-2685] and fewer thorax [5618, 95% CI 4212-6272], upper [3804, 95% CI 1781-4803] and lower extremity [2791, 95% CI 2216-3256] injuries in frontal crashes. Results indicate that age provides the greater relative contribution to injury when compared to gender and BMI, especially for thorax and head injuries.

CONCLUSIONS

Restraint systems that account for the differential injury risks associated with age, BMI and gender could have a meaningful effect on injury in motor-vehicle crashes. Computational models of humans that represent older, high BMI, and female occupants are needed for use in simulations of particular types of crashes to develop these restraint systems.

Does Obesity Increase the Risk of Injury or Mortality in Motor Vehicle Crashes? A Systematic Review and Meta-Analysis

The objective of this review was to assess the risk of obesity in injuries and fatalities resulting from motor vehicle crash (MVC), as compared with individuals with a normal-range body mass index. A systematic review of the literature was conducted yielding 824 potential studies. Nine of these studies met our inclusion criteria. Meta-analyses examining obesity as a risk factor for various injury types and risk of fatality were conducted using data from these studies. Obesity was associated with higher fatality risk (odds ratio [OR] = 1.89, 95% confidence interval [CI] = 1.51-2.37, P = .0001; pooled estimate from 6 studies), and increased risk of lower extremity fractures (OR = 1.39, 95% CI = 1.18-1.65, P = .0001; pooled estimate from 2 studies). No significant differences were observed when considering abdominal injuries or pelvic fractures. Interestingly, for head injuries obesity was a protective factor (OR = 0.67, 95% CI = 0.46-0.97, P = .0001; pooled data from 3 studies). Evidence strongly supports the association of obesity with higher fatality and fractures of the lower extremities in MVCs. Contrary to our hypothesis, 3 studies showed that obesity was a protective factor in reducing head injuries. Furthermore, the review shows that obesity was not a risk factor of MVC-related pelvic fractures and abdominal injuries.

Risk of thoracic injury from direct steering wheel impact in frontal crashes

BACKGROUND

The combination of airbag and seat belt is considered to be the most effective vehicle safety system. However, despite the widespread availability of airbags and a belt use rate of more than 85%, US drivers involved in crashes continue to be at risk of serious thoracic injury. The objective of this study was to determine the influence of steering wheel deformation on driver injury risk in frontal automobile crash.

METHODS

The analysis is based on cases extracted from the National Automotive Sampling System Crashworthiness Data System database for case years 1993 to 2011. The approach was to compare the adjusted odds of frontal crash injury experienced by drivers in vehicles with and without steering wheel deformation.

RESULTS

Among frontal crash cases with belted drivers, observable steering wheel deformation occurred in less than 4% of all cases but accounted for 30% of belted drivers with serious (Abbreviated Injury Scale [AIS] score, 3+) thoracic injuries. Similarly, steering wheel deformation occurred in approximately 13% of unbelted drivers but accounted for 60% of unbelted drivers with serious thoracic injuries. Belted drivers in frontal crashes with steering wheel deformation were found to have two times greater odds of serious thoracic injury. Unbelted drivers were found to have four times greater odds of serious thoracic injury in crashes with steering wheel deformation. In frontal crashes, steering wheel deformation was more likely to occur in unbelted drivers than belted drivers, as well as higher severity crashes and with heavier drivers.

CONCLUSION

The results of the present study show that airbag deployment and seat belt restraint do not completely eliminate the possibility of steering wheel contact. Even with the most advanced restraint systems, there remains an opportunity for further reduction in thoracic injury by continued enhancement to the seat belt and airbag systems. Furthermore, the results showed that steering wheel deformation is an indicator of potential serious thoracic injury and can be useful to prehospital personnel in improving the diagnosis of serious injuries.

LEVEL OF EVIDENCE

Prognostic study, level III.

A statistical human rib cage geometry model accounting for variations by age, sex, stature and body mass index

In this study, we developed a statistical rib cage geometry model accounting for variations by age, sex, stature and body mass index (BMI). Thorax CT scans were obtained from 89 subjects approximately evenly distributed among 8 age groups and both sexes. Threshold-based CT image segmentation was performed to extract the rib geometries, and a total of 464 landmarks on the left side of each subject׳s ribcage were collected to describe the size and shape of the rib cage as well as the cross-sectional geometry of each rib. Principal component analysis and multivariate regression analysis were conducted to predict rib cage geometry as a function of age, sex, stature, and BMI, all of which showed strong effects on rib cage geometry. Except for BMI, all parameters also showed significant effects on rib cross-sectional area using a linear mixed model. This statistical rib cage geometry model can serve as a geometric basis for developing a parametric human thorax finite element model for quantifying effects from different human attributes on thoracic injury risks.

Body mass index and the risk of injury in adults: a cross-sectional study

OBJECTIVES

To investigate the association between body mass index (BMI) and the risk of nonfatal body injury.

METHODS

We analyzed data from 113,203 adults who participated in the Canadian Community Health Survey conducted in 2009-2010. Log-binomial models were used to estimate crude and adjusted relative risks of the association between BMI and the risk of body injury for men and women.

RESULTS

Of 113,203 adult participants, 15,194 had self-reported body injuries during the past 12 months, with a 12-month cumulative incidence of 13.7% (weighted to Canadian population). There was a significant interaction between gender and BMI in relation to the risk of body injury, and therefore, analyses were stratified by gender. For women, we found a significant association between BMI and an increased risk of body injury. Women with an increased BMI had a significant increased risk of body injuries as compared with those with normal weight (adjusted relative risk: 1.13, 95% confidence interval (CI)=1.02-1.25 for BMI 30.0-34.9 kg m(-)(2); 1.17, 95% CI=1.00-1.37 for BMI 35.0-39.9 kg m(-)(2); 1.41, 95% CI=1.16-1.69 for BMI ⩾ 40 kg m(-)(2)). A reduced risk of injury was observed in underweight women. There was no significant association between BMI and the risk of body injury for men. Obese persons of both gender were more likely to suffer injuries to the knee and lower leg, and in less demanding activities such as household chores or using the stairs.

CONCLUSIONS

We therefore conclude that increased BMI may be a risk factor for body injury in women, but not in men.

Complex Interaction between Obesity and Trauma

Trauma and obesity are large-scale epidemics that can be associated with significant morbidity and mortality. In few studies, it has noted that there is the ‘obesity paradox’ (obesity has been found to be protective against mortality) due to certain causes, i.e. heart failure or cardiovascular disease. Subcutaneous fat can show great variability between individuals and increased subcutaneous fat may be protective against injuries by cushioning the internal abdominal organs against injurious forces in road traffic accidents. Many factors including the body fat distribution, body shape, and center of gravity may play an important role in the different injury patterns and severity of injury between men and women. A better understanding of how obesity influences trauma related injuries not only will help to improve the outcome but also foster the development of interventions to address the most salient and modifiable risk factors to reduce obesity related morbidity and mortality. In present article, we review the relevant literature with special considerations to understand the interactions of obesity and trauma with their impact on patient management and outcomes.

How to cite this article

Agrawal A. Complex Interaction between Obesity and Trauma. Panam J Trauma Crit Care Emerg Surg 2014;3(3):109-113.

Characterization of vertebral angle and torso depth by gender and age groups with a focus on occupant safety

OBJECTIVE

The human body changes as it becomes older. The automotive safety community has been interested in understanding the effect of age on restraint performance. Focus has been placed on characterizing the body's structural changes associated with age and gender. In this study, spine alignment and torso depth were assessed, because both variables have been shown to affect injury risk.

METHODS

The data was obtained from computed tomography (CT) scans of more than 24,000 patients aged 16 and older. The data consisted of thoracic and lumbar vertebral angles relative to a fixed plane, as well as vertebra-to-front skin and spine-to-back skin distances. Angle measurements were taken in the sagittal plane at each vertebra level from T1 to L5; distance measurements were taken from T6 to L5. The data were analyzed as a function of gender and age with the young group defined as 16 to 29 years old and the older group as 75 and up.

RESULTS

Vertebral angles were different depending on location. They varied from -24.5 ± 8.9° at T2 to 12.2 ± 5.6° at L1. The vertebral angles also varied with age. Angles in the older male group were 1.74 times larger at T1 and 2.03 times larger at T7 than in the young male group. Similar findings were observed for females. The effect of age and gender was modeled with forward/backward selection using a regression model. The vertebra-to-front skin distance also differed depending on vertebral level. It was highest at T10 at 162.5 ± 30.9 mm and lowest at L4 at 125.3 ± 37.3 mm for the entire study population. On average, males had larger distances than females. The spine-to-back distances were greatest in the lumbar area. The spine-to-back distance increased with lower vertebral level, regardless of age. The vertebral angle and distance data were analyzed for a male subgroup approximating the height and weight of a 50th percentile male dummy. The results showed that the vertebra-to-front skin distance increased with age. There was not a clear trend for the spine-to-back skin distance and L1 vertebral angle.

CONCLUSIONS

The changes in the vertebral angles, as well as the anterior and posterior spine-to-skin distances along the sagittal plane, were determined as a function of age and gender. The effect was greatest in the mid-thoracic area. Spine alignment and body shape differences need to be considered in human mathematical models used to develop safety countermeasures for the older population, because they may affect the loading path and lead to different seating postures or belt positioning. Supplemental materials are available for this article. Go to the publisher's online edition of Traffic Injury Prevention to view the supplemental file.

Prediction of thoracic injury severity in frontal impacts by selected anatomical morphomic variables through model-averaged logistic regression approach

This study resulted in a model-averaging methodology that predicts crash injury risk using vehicle, demographic, and morphomic variables and assesses the importance of individual predictors. The effectiveness of this methodology was illustrated through analysis of occupant chest injuries in frontal vehicle crashes. The crash data were obtained from the International Center for Automotive Medicine (ICAM) database for calendar year 1996 to 2012. The morphomic data are quantitative measurements of variations in human body 3-dimensional anatomy. Morphomics are obtained from imaging records. In this study, morphomics were obtained from chest, abdomen, and spine CT using novel patented algorithms. A NASS-trained crash investigator with over thirty years of experience collected the in-depth crash data. There were 226 cases available with occupants involved in frontal crashes and morphomic measurements. Only cases with complete recorded data were retained for statistical analysis. Logistic regression models were fitted using all possible configurations of vehicle, demographic, and morphomic variables. Different models were ranked by the Akaike Information Criteria (AIC). An averaged logistic regression model approach was used due to the limited sample size relative to the number of variables. This approach is helpful when addressing variable selection, building prediction models, and assessing the importance of individual variables. The final predictive results were developed using this approach, based on the top 100 models in the AIC ranking. Model-averaging minimized model uncertainty, decreased the overall prediction variance, and provided an approach to evaluating the importance of individual variables. There were 17 variables investigated: four vehicle, four demographic, and nine morphomic. More than 130,000 logistic models were investigated in total. The models were characterized into four scenarios to assess individual variable contribution to injury risk. Scenario 1 used vehicle variables; Scenario 2, vehicle and demographic variables; Scenario 3, vehicle and morphomic variables; and Scenario 4 used all variables. AIC was used to rank the models and to address over-fitting. In each scenario, the results based on the top three models and the averages of the top 100 models were presented. The AIC and the area under the receiver operating characteristic curve (AUC) were reported in each model. The models were re-fitted after removing each variable one at a time. The increases of AIC and the decreases of AUC were then assessed to measure the contribution and importance of the individual variables in each model. The importance of the individual variables was also determined by their weighted frequencies of appearance in the top 100 selected models. Overall, the AUC was 0.58 in Scenario 1, 0.78 in Scenario 2, 0.76 in Scenario 3 and 0.82 in Scenario 4. The results showed that morphomic variables are as accurate at predicting injury risk as demographic variables. The results of this study emphasize the importance of including morphomic variables when assessing injury risk. The results also highlight the need for morphomic data in the development of human mathematical models when assessing restraint performance in frontal crashes, since morphomic variables are more "tangible" measurements compared to demographic variables such as age and gender.

Effectiveness of booster seats compared with no restraint or seat belt alone for crash injury prevention

OBJECTIVES

The objective was to evaluate the effectiveness of belt-positioning booster seats, compared with no restraint use and with seat belt use only, during motor vehicle crashes among U.S. children.

METHODS

This was a retrospective matched cohort study with data from the 1998 through 2009 National Automotive Sampling System (NASS) Crashworthiness Data System (CDS). The study sample consisted of children aged 0 to 10 years who were not seated in the front seat of the vehicle. We used Cox proportional hazards models to estimate the risk of overall, fatal, and regional body injury.

RESULTS

Children using seat belts in belt-positioning booster seats experienced less overall injury (Injury Severity Score [ISS] > 0, adjusted risk ratio [RR] = 0.73, 95% confidence interval [CI] = 0.55 to 0.96; Abbreviated Injury Scale [AIS] score of 2 or higher, adjusted RR = 0.30, 95% CI = 0.16 to 0.58; ISS > 8, adjusted RR = 0.19, 95% CI = 0.06 to 0.56), and less injury in most body regions except the neck (adjusted RR = 4.79, 95% CI = 1.43 to 16.00) than did children with no restraint use. Children using seat belts in belt-positioning booster seats had an equal risk of injury but higher risks of neck (adjusted RR = 1.86, 95% CI = 1.02 to 3.40) and thorax (adjusted RR = 2.86, 95% CI = 1.33 to 6.15) injury than did children restrained by seat belts only.

CONCLUSIONS

Children using belt-positioning booster seats appear to experience a higher risk of AIS > 0 injury to the neck and thorax than do children using seat belts only. Future research should examine whether the observed increase in neck and thorax injuries can be attributed to improper use of booster seats.

Effects of BMI on the risk and frequency of AIS 3+ injuries in motor-vehicle crashes

OBJECTIVE

Determine the effects of BMI on the risk of serious-to-fatal injury (Abbreviated Injury Scale ≥ 3 or AIS 3+) to different body regions for adults in frontal, nearside, farside, and rollover crashes.

DESIGN AND METHODS

Multivariate logistic regression analysis was applied to a probability sample of adult occupants involved in crashes generated by combining the National Automotive Sampling System (NASS-CDS) with a pseudoweighted version of the Crash Injury Research and Engineering Network database. Logistic regression models were applied to weighted data to estimate the change in the number of occupants with AIS 3+ injuries if no occupants were obese.

RESULTS

Increasing BMI increased risk of lower-extremity injury in frontal crashes, decreased risk of lower-extremity injury in nearside impacts, increased risk of upper-extremity injury in frontal and nearside crashes, and increased risk of spine injury in frontal crashes. Several of these findings were affected by interactions with gender and vehicle type. If no occupants in frontal crashes were obese, 7% fewer occupants would sustain AIS 3+ upper-extremity injuries, 8% fewer occupants would sustain AIS 3+ lower-extremity injuries, and 28% fewer occupants would sustain AIS 3+ spine injuries.

CONCLUSIONS

Results of this study have implications on the design and evaluation of vehicle safety systems.

A computational study of injury severity and pattern sustained by overweight drivers in frontal motor vehicle crashes

The objective of this study was to examine the role of body mass and subcutaneous fat in injury severity and pattern sustained by overweight drivers. Finite element models were created to represent the geometry and properties of subcutaneous adipose tissue in the torso with data obtained from reconstructed magnetic resonance imaging data-sets. The torso adipose tissue models were then integrated into the standard multibody dummy models together with increased inertial parameters and sizes of the limbs to represent overweight occupants. Frontal crash simulations were carried out considering a variety of occupant restraint systems and regional body injuries were measured. The results revealed that differences in body mass and fat distribution have an impact on injury severity and pattern. Even though the torso adipose tissue of overweight subjects contributed to reduce abdominal injury, the momentum effect of a greater body mass of overweight subjects was more dominant over the cushion effect of the adipose tissue, increasing risk of other regional body injuries except abdomen. Through statistical analysis of the results, strong correlations (p < 0.01) were found between body mass index and regional body injuries except neck injury. The analysis also revealed that a greater momentum of overweight males leads to greater forward torso and pelvic excursions that account for higher risks (p < 0.001) of head, thorax and lower extremity injury than observed in non-overweight males. The findings have important implications for improving the vehicle and occupant safety systems designed for the increasing global obese population.

General characteristics and risk factors of cardiovascular disease among interstate bus drivers

Workers in the transportation industry are at greater risk of an incorrect diet and sedentary behavior. The aim of our study was to characterize a population of professional bus drivers with regard to clinical and demographic variables, lipid profile, and the presence of cardiovascular risk factors. Data from 659 interstate bus drivers collected retrospectively, including anthropometric characteristics, systolic and diastolic blood pressure, lipid profile, fasting blood glucose, meatoscopy, and audiometry. All participants were male, with a mean age of 41.7 ± 6.9 years, weight of 81.4 ± 3.3 kg, and BMI 27.2 ± 3.3 Kg/m²; the mean abdominal and neck circumferences were 94.4 ± 8.6 cm and 38.9 ± 2.2  cm; 38.2% of the sample was considered hypertensive; mean HDL cholesterol was 47.9 ± 9.5 mg/dL, mean triglyceride level was 146.3 ± 87.9 mg/dL, and fasting glucose was above 100 mg/dL in 249 subjects (39.1%). Drivers exhibited reduced audiometric hearing at 4-8 kHz, being all sensorineural hearing loss. The clinical characterization of a young male population of interstate bus drivers revealed a high frequency of cardiovascular risk factors, as obesity, hypertension, hyperlipidemia, and hyperglycemia, as well as contributing functional characteristics, such as a low-intensity activity, sedentary behavior, long duration in a sitting position, and high-calorie diet, which lead to excessive weight gain and associated comorbidities.

Obesity in trauma patients: correlations of body mass index with outcomes, injury patterns, and complications

Current understanding of the effects of obesity on trauma patients is incomplete. We hypothesized that among older trauma patients, obese patients differ from nonobese patients in injury patterns, complications, and mortality. Patients older than 45 years old presenting to a Level I trauma center were included in this retrospective database analysis (n = 461). Body mass index (BMI) groups were defined as underweight less than 18.5 kg/m(2), normal 18.5 to 24.9 kg/m(2), overweight 25.0 to 29.9 kg/m(2), or obese greater than 30 kg/m(2). Injury patterns, complications, and outcomes were analyzed using univariate analyses, multivariate logistic regression, and Kaplan-Meier survival analysis. Higher BMI is associated with a higher incidence of torso injury and proximal upper extremity injuries in blunt trauma (n = 410). All other injury patterns and complications (except anemia) were similar between BMI groups. The underweight (BMI less than 18.5 kg/m(2)) group had significantly lower 90-day survival than other groups (P < 0.05). BMI is not a predictor of morbidity or mortality in multivariate analysis. Among older blunt trauma patients, increasing BMI is associated with higher rates of torso and proximal upper extremity injuries. Our study suggests that obesity is not an independent risk factor for complications or mortality after trauma in older patients. Conversely, underweight trauma patients had a lower 90-day survival.

Obesity and non-fatal motor vehicle crash injuries: sex difference effects

Background

Obesity and motor vehicle crash (MVC) injuries are two parallel epidemics in the United States. An important unanswered question is if there are sex differences in the associations between the presence of obesity and non-fatal MVC injuries.

Objectives

To further understand the association between obesity and non-fatal motor vehicle crash injuries, particularly the sex differences in these relations.

Methods

We examined this question by analyzing data from the 2003 to 2007 National Automotive Sampling System Crashworthiness Data System (NASS CDS). A total of 10, 962 drivers who were aged 18 years or older and who survived frontal collision crashes were eligible for study.

Results

Male drivers experienced a lower rate of overall non-fatal MVC injuries than did female drivers (38.1% vs. 52.2%) but a higher rate of severe injuries (0.7% vs. 0.2%). After adjusting for change in velocity (ΔV) during the crashes, obese male drivers showed a much higher risk [logistic coefficients of BMI for moderate, serious, and severe injury are 0.0766, 0.1470, and 0.1792, respectively; all p<0.05] of non-fatal injuries than did non-obese male drivers and these risks increased with injury severity. Non-fatal injury risks were not found to be increased in obese female drivers. The association between obesity and risk of non-fatal injury was much stronger for male drivers than for female drivers.

Conclusion

The higher risk of non-fatal MVC injuries in obese male drivers might result from their different body shape and fat distribution compared with obese female drivers. Our findings should be considered for obesity reduction, traffic safety evaluation and vehicle design for obese male drivers and provide testable hypotheses for future studies.

Preventing road deaths--time for data

In this month's editorial, the PLoS Medicine Editors call for better data to support policy changes that could reduce the huge global burden of death and injury from road traffic crashes.