Clinical Trauma Severity of Indoor and Outdoor Injurious Falls Requiring Emergency Medical Service Response

Background: Injurious falls represent a significant public health burden. Research and polices have primarily focused on falls occurring indoors despite evidence that outdoor falls account for 47–58% of all falls requiring some medical attention. This study compared the clinical trauma severity of indoor versus outdoor injurious falls requiring Emergency Medical Services (EMS) response. Methods: Using the 2019 National Emergency Medical Services Information System (NEMSIS) dataset, we identified the location of patients injured from falls that required EMS response. We classified injury severity using 1) the Revised Trauma Score for Triage (T-RTS): ≤ 11 indicated the need for transport to a Trauma Center; 2) Glasgow Coma Scale (GCS): ≤8 and 9–12 indicated moderate and severe neurologic injury; and 3) patient clinical acuity by EMS: Dead, Critical, Emergent, Low. Results: Of 1,854,909 encounters for patients with injurious falls, the vast majority occurred indoors (n=1,596,860) compared to outdoors (n=152,994). The proportions of patients with moderate or severe GCS scores, were comparable between those with indoor falls (3.0%) and with outdoor falls on streets or sidewalks (3.8%), T-RTS scores indicating need for transport to a Trauma Center (5.2% vs 5.9%) and EMS acuity rated as Emergent or Critical (27.7% vs 27.1%).Injurious falls were more severe among male patients compared to females: and males injured by falling on streets or sidewalks had higher percentages for moderate or severe GCS scores (4.8% vs 3.6%) and T-RTS scores indicating the need for transport to a Trauma Center (7.3% vs 6.5%) compared to indoor falls. Young and middle-aged patients whose injurious falls occurred on streets or sidewalks were more likely to have a T-RTS score indicating the need for Trauma Center care compared to indoor falls among this subgroup. Yet older patients injured by falling indoors were more likely to have a T-RTS score indicating the need for Trauma Center than older patients who fell on streets or sidewalks. Conclusions: There was a similar proportion of patients with severe injurious falls that occurred indoors and on streets or sidewalks. These findings suggest the need to determine outdoor environmental risks for outdoor falls to support location-specific interventions.

A primary reason for the lack of evidence to determine environmental risk factors for outdoor falls, and particularly at the populationlevel, is limitations in the surveillance of falls.The three primary public health surveillance systems in the U.S. for fall-related injuries are the CDC's Web-Based Injury Statistics Query and Reporting System (WISQARS), the Behavioral Risk Factor Surveillance System (BRFSS) and the National Health Interview Survey (NHIS) and yet none of these systems routinely provide data on the locations in which falls occur (Moreland et al., 2020;Timsina et al., 2017; WISQARS (Web-Based Injury Statistics Query and Reporting System) | Injury Center | CDC, 2023).While the NHIS has been used to examine outdoor falls, these analyses are 10-25 years old, likely because the location of the fall is determined by intensive coding of unstructured narrative texts, which makes use of these data cumbersome to analyze (Timsina et al., 2017).To improve the surveillance of outdoor falls, Rundle et al. (2023) developed a methodology to identify injurious falls by indoor versus outdoor location using EMS clinical and administrative data from the National Emergency Medical Services Information System (NEMSIS) (Rundle et al., 2023).Among the 1,854,909 injuries from falls that required an EMS response in 2019, 129,408 of these fall injuries were identi ed as occurring outdoors on streets and sidewalks, a number which is 70% higher than the number of pedestrians reportedly injured by automobiles (Li et al., 2006; National Highway Tra c Safety Administration, n.d.; Timsina et al., 2017).While establishing this surveillance method was a critical rst step towards developing interventions to reduce outdoor falls, epidemiological data are needed to improve understanding of the public health and clinical burden of outdoor falls.
There are very few available studies to compare the severity of indoor and outdoor falls, with the focus of these being among the older adult population (Bath & Morgan, 1999 2016) study of older U.S. trauma center patients who sustained outdoor falls had a higher frequency of open wounds and head injuries compared to indoor falls, but no signi cant difference on the injury severity score (ISS) (Chippendale et al., 2017).Kim (2016) found that outdoor falls led to a higher proportion of head and neck injuries than indoor falls among older emergency department patients across 20 hospitals in Korea (Kim, 2016).Jung et al. (2017) determined that the likelihood of severe injury, as determined by level of care, from outdoor falls in older adults was higher in men compared to women (Jung et al., 2018).These studies were limited by examining only individuals admitted to a hospital, and none were of a nationally representative sample.Furthermore, assessment of outcomes and severity of falls varied across these studies.Improved understanding of the clinical severity for fall injuries is critical to determining the short-and long-term burdens of 1) morbidities and disability among individuals (Stewart Williams et al., 2015) and 2) health care utilization needs of different communities (Eliacin et al., 2021;Korley et al., 2016), particularly in light of potential differences across sociodemographic groups (Chun Fat et al., 2019;Sharma et al., 2018).In the immediate setting following an injury, clinical severity scoring tools have been recommended, including the Revised Trauma Score for Triage (T-RTS) and Glasgow Coma Scale (GCS), to help guide on-scene EMS to determine the severity of the injury and optimal care response for the individual (Champion et al., 1989;Newgard et al., 2022).However, there are no population-level studies that have characterized the distribution of such scores in the assessment of severity of indoor versus outdoor injurious falls.
National surveillance data comparing indoor and outdoor injurious falls are critical to the development of person-centered, communityspeci c programs and policies to prevent serious falls.Data from EMS responses on the severity and level of care for indoor and outdoor injurious falls could be particularly informative from a healthcare resource perspective.Here we use 2019 national U.S. EMS data to compare the clinical trauma severity of indoor versus outdoor injurious falls, and further to examine these patterns by patient demographic characteristics.

Study Design
This cross-sectional study of EMS records from the 2019 National Emergency Medical Services Information System (NEMSIS) Public-Release Research Dataset included 1,854,909 occurrences of falls requiring EMS response across US states and territories (Rundle et al., 2023).

Data Source
NEMSIS is the national system to collect and standardize data from EMS agencies across the US.The National Highway Tra c Safety Administration O ce for Emergency Medical Services provides these NEMSIS data are public release, de-identi ed, and HIPAA exempt data released by the University of Utah, as such further Institutional Review Board (IRB) review was not requested (Dawson, 2006;Ehlers et al., 2023).The use of NEMSIS to identify falls and locations of falls have been previously described and includes a robust approach to identifying overall injurious falls and to identifying falls for which syncope (heat-related and non-heat related syncope) and heat illness were contributing factors.(Rundle et al., 2023).EMS data entry into NEMSIS must abide by the standards set forth by the NHTSA O ce of EMS and outlined in the NEMSIS data dictionary (https://nemsis.org/media/nemsis_v3/release-3.5.0/DataDictionary/PDFHTML/EMSDEMSTATE/index.html)(V3 Data Dictionaries & XSD, n.d.).

Study Variables and Inclusion Criteria
Detailed methods for inclusion criteria and coding of fall locations (indoor, outdoor -not on street or sidewalk, outdoor -on street or sidewalk, indoor/outdoor unclear), patient demographic variables, and on-scene clinical measures (e.g.patient acuity) can be found in Rundle et al (Rundle et al., 2023).Brie y, we used NEMSIS variables ePatient 13, ePatient 15 and eSituation 13 to de ne patient sex (male, female), and age groups (0-20, 21-30, 31-40, 41-50, 51-60, 61-65, 66-70, 71-75, 76-80, 81-85, 86-90 and 91 + years), respectively.Falls with EMS notations of seizures have been removed from the analyses.NEMSIS data includes the patient's clinical acuity, rated by EMS, which is classi ed as: Dead Without Resuscitation Efforts, Critical, Emergent, Low, Unknown.NEMSIS data were also used to calculate the Revised Trauma Score for Triage (T-RTS) and the Glasgow Coma Scale (GCS).The T-RTS, GCS and patient acuity data were used to characterize the severity of the injuries as observed by the EMS clinician on scene.When the tests used to calculate the GCS and the T-RTS were administered multiple times for a patient, the mean of all administrations were used.

Revised Trauma Score for Triage (T-RTS)
The Revised Trauma score for Triage to a Trauma Center (T-RTS) is a modi ed version of the original Trauma Score, that is more reliable and excludes capillary re ll and respiratory expansion which are more di cult to assess in the eld by EMS (Champion et al., 1989).The T-RTS can be used by EMS to make decisions on trauma care based on the severity of patient injuries (Lichtveld et al., 2008).For each patient, we calculated the mean T-RTS by summing the average value for GCS, systolic blood pressure, and respiratory rate.Champion and colleagues evaluated T-RTS cut-points based upon survival probabilities to create decision rules for patients to be triaged to a trauma center (Champion et al., 1989).Decision Rule 2 was used for the present study to categorize the T-RTS score into: ≤11, indicated need for immediate transport to a Trauma Center designated hospital; >11 does not.As blood pressure may be arti cially lowered by anti-hypertensive medications, the use of which differs by age group, the validity of the T-RTS may vary by age.Therefore, assessment of the GCS alone offers a second measure of injury severity that is independent of blood pressure.

Glasgow Coma Scale (GCS)
The Glasgow Coma Scale (GCS) is a well-established measure of neurological status used for risk strati cation in acute neurosurgical or traumatic injuries; the scale ranges from 3 to 15 and is calculated by summing the values for eye opening, verbal response, and motor response for each patient. 11In contemporary clinical practice, the GCS is used to determine the risks of mortality and morbidity, and more urgently to guide acute clinical management.We calculated the mean Glasgow Coma Scale (GCS) by summing the average value for eye opening, verbal response, and motor response for each patient.GCS ranges from 3 to 15, and for this analysis, GCS we use the widely used classi cations for injury severity: as severe, ≤ 8; moderate, 9-12; and minor, ≥ 13 (Jain & Iverson, 2024).

Statistical Analyses
We conducted descriptive analyses for all EMS encounters for injurious falls by comparing the T-RTS, GCS, and patient acuity classi cations by fall location, and further described these analyses by patient demographics.Due to the large size of this dataset, we did not include measures of statistical signi cance and instead allow the readers to make interpretations based on practical relevance in the differences.We conducted all analyses in R statistical software (v4.3.1;R Core Team 2023).

Results
In total 1,854,909 injuries from falls that required an EMS response were identi ed in the 2019 NEMSIS data.As reported previously (Rundle et al., 2023) and here in Table 1, of these falls the majority, 1,596,860, occurred indoors, 152,994 falls occurred outdoors, of which 129,408 occurred on streets and sidewalks.For 53,700 falls, the indoor versus outdoor status of the fall location could not be ascertained from the coded data, and for 51,355 the location data were not reported.Overall, 28% of fall patients injured by a fall had an EMS acuity rating of Critical or Emergent and 0.1% Dead at Scene (see Table 1).There were a minority of injured fall patients (n = 51,422; 3.0%) who had moderate or severe GCS scores and a minority of patients (n = 84,220; 5.2%) who had a T-RTS score indicating the need for transport to a Trauma Center.The proportion of patients injured by falling indoors who had an Emergent or Critical acuity rating was similar to the proportion of patients injured by falls occurring outdoors on streets or sidewalks (27.7% vs. 27.1%).Similarly, the proportion of patients injured by falling indoors and having moderate or severe GCS scores was comparable to the proportion of patients with moderate or severe GCS scores injured by falling on a street or sidewalk (3.0% vs. 3.8%).Likewise, the proportion of injured patients who fell indoors and who had a T-RTS score indicating the need for transport to a Trauma Center was comparable to the proportion of injured patients who had a T-RTS score indicating the need for transport to a Trauma Center and fell outdoors on a street or sidewalk (5.2% vs 5.9%).Patients injured by falling outdoors not on a street or sidewalk had a lower percentage for moderate or severe GCS scores (2.2% vs. 3.8%) and for T-RTS scores indicating the need for transport to a Trauma Center (4.4% vs 5.9%) compared to percentages for those injured by falling outdoors on streets or sidewalks, but the reverse pattern was true for patients injured by falls with an Emergent or Critical patient acuity (31.1% vs 27.1%).

Discussion
The majority of fall injuries to which EMS responded in 2019 occurred indoors, with the second largest category occurring outdoors on streets or sidewalks.However, the proportions for patients who had fall injuries rated as Emergent or Critical, having moderate or severe GCS scores and having a T-RTS score indicating the need for transport to a Trauma Center were similar across indoor and outdoor locations of falls.Given the large numbers of falls that occur indoors and among older persons, it is appropriate that falls prevention guidelines and recommendations have focused on these falls ("Guideline for the Prevention of Falls in Older Persons. American Geriatrics Society, British Geriatrics Society, and American Academy of Orthopaedic Surgeons Panel on Falls Prevention," 2001; Panel on Prevention of Falls in Older Persons, American Geriatrics Society and British Geriatrics Society, 2011).However, the comparable trauma severity of outdoor injurious falls to those that occur indoors and the greater severity of falls on streets and sidewalks among young and middle-aged patients suggests that additional public health attention is needed to identify modi able outdoor environmental risk factors to prevent outdoor falls.
This study found that the proportion of severe outdoor falls on streets and sidewalks was higher among men compared to women.
This nding may be explained by differences in the age and physical activity status for men and women falling outside versus inside (Duckham et al., 2013;Kelsey et al., 2012;Timsina et al., 2017).Timsina and colleagues (2017) found that young and middle-age men were more likely to fall outside, whereas older females are were more likely to fall inside (Timsina et al., 2017).Young men were also most likely to fall while engaging in vigorous activity, and thus the potentially higher speed and impact of the activities at the time of falling may result in more serious fall injuries for this subgroup.An additional explanation is that men of all ages tend to consume more alcohol than women, and acute alcohol consumption is associated with greater risk of injurious falls by impacting balance control and cognition (Taylor et al., 2010).One study found that alcohol-related fall injury presentations to emergency departments (ED) were more prevalent among men and younger patients, and were more severe based on triage scale ratings and admissions to the ED compared to non-alcohol-related injuries (Woods et al., 2019).An additional study of outdoor falls similarly found that the proportion of men and the rate of alcohol consumption were higher in severe outdoor falls compared to non-severe falls (Jung et al., 2018).Future work in this area should examine the role of alcohol in the severity of injurious falls by location to support place-based intervention strategies and policies.Falls that occur on streets and sidewalks that involve alcohol may be in close proximity to businesses that serve alcohol, which is consistent with a higher density of alcohol serving establishments being linked to increased alcohol consumption and increased pedestrian injury from motor vehicles (Gruenewald et al., 1993).However, the association between injurious falls on streets and sidewalks and proximity to alcohol serving establishment has yet to be examined and is an area ripe for We also found that outdoor falls on streets or sidewalks were more likely to result in severe injury among young and middle-aged individuals compared to indoor falls among this age subgroup, but this pattern was reversed for older adults.This nding may also be explained by the evidence showing a higher proportion of alcohol involved falls among younger adults and greater severity of these falls, which may be occurring on streets or sidewalks near alcohol serving establishments or nightlife districts (Woods et al., 2019).
Indoor falls may appear to be more frequently severe among older adults due to a form of selection bias.The population of older adults that fall indoors may be more likely to be frail, while those who fall while outdoors may be in better overall health (Kelsey et al., 2012).This is consistent with ndings that suggest that outdoor falls are experienced more by healthy and activity individuals, compared to greater risk of falling indoors for individuals in poorer health who may experience worse injury outcomes.(Kelsey et al., 2010;Li et al., 2006).There may also be differences in the types of surfaces (e.g., wooden oor, grass) or oor characteristics adults are falling on indoors compared to outdoors which could in uence injury severity; however, studies are lacking in this area of research (Jung et al., 2018).
This analysis suggests that outdoor falls, particularly on streets and sidewalks, present a signi cant medical and public health burden.Current fall prevention guidelines did not explicitly examine the impact of outdoor environments falls (Montero-Odasso et al., 2022; Panel on Prevention of Falls in Older Persons, American Geriatrics Society and British Geriatrics Society, 2011) and pedestrian safety policies are largely centered around pedestrian injuries from motor vehicles with minimal attention to outdoor falls, even though these two injury types occur in the same or adjacent physical environments (Evenson et al., 2018).This may be due to the limited empirical evidence available to determine modi able environmental risk factors for outdoor falls (Schepers et al., 2017).Li et al. (2006) found that among a sample of U.S. adults, participants subjectively reported that most (73%) of outdoor falls were due to environmental factors such as the condition of the walking surface, and usually occurred on sidewalks, curbs and streets (Li et al., 2006).Yet, rigorous epidemiological studies are needed to identify potential environmental hazards on sidewalks and streets such as street trees that may cause buckling or damage to sidewalks and increase fall risk (Bentley, 1998;Bentley & Haslam, 2001;David & Freedman, 1990;Fothergill et al., 1995;Hunt et al., 1991).This evidence would inform policy interventions to prevent outdoor fall injuries that we show are comparably severe to indoor fall injuries.
The primary strength of this study is the use of NEMSIS data, which provides a well-documented national census of health encounters requiring an EMS response.The data include pertinent sociodemographic and clinical information, and variables that can be used to code the location of the encounter, eliminating the need to incorporate additional data sources.The severity outcomes used in this analysis relied on data recorded in the EMS notes with varying degrees of missingness.We were unable to calculate GCS for 7.5% of patients and T-RTS for 13.0% of patients, and 25.9% of patients did not have an acuity measure reported.This study is also limited by missing data on fall location.The coding schema used to classify fall location does not make use of narratives and text notes created by EMS personnel, and therefore may result in misclassi cation of fall location.Machine learning for natural language processing applied to EMS narrative notes could supplement the ICD 10-based case-nding algorithm used in this study and increase the sensitivity of identifying fall location from EMS data (Mayampurath et al., 2021;Zhao et al., 2021).Lastly, the quality of data provided to NEMSIS may vary by region, EMS service and third-party data management systems.Combined these limitations may have caused underestimates of the numbers of falls occurring outdoors and the severity of falls by location.

Conclusion
In conclusion, these data show that there is a signi cant clinical burden associated with outdoor falls, and that the proportion of severe life-threatening injuries from falls that occur outdoors is comparably substantial to that for falls that occur indoors.These ndings represent a major public concern as the aging population projects an expected growth of persons 65 years and older by 22% by 2040, and the number of injurious falls and associated healthcare costs will simultaneously increase (2021 Pro le of Older Americans, 2022).Indeed, recent data already shows this rising incidence of falls of 1.5% per year from 2016-2019 (Hoffman et al., 2022).These concerns emphasize the need to address outdoor falls in current fall prevention guidelines, and to improve surveillance tools for monitoring outdoor falls and associated risk factors and outcomes.

Table 1
Descriptive statistics for EMS Encounters for Reported Location of Fall Injuries by Patient Acuity, GCS and T-RTS scores.1 1 GCS, Glasgow Comma Scale; T-RTS, Revised Trauma Score for TriageMale patients injured by falls were more likely to have an acuity rated as Critical or Emergent (29.4% vs. sidewalks and indoors locations.The proportions for injurious falls for which patient acuity was rated Critical or Emergent were similar for falls occurring on streets or sidewalks and for falls occurring indoors among both male (28.2% vs 29.4%) and female patients (25.4% vs 26.5%).

Table 2 Descriptive
Statistics for EMS Encounters for Reported Location of Fall Injuries by Patient Acuity, GCS and T-RTS Scores, Categorized by Sex.1 GCS, Glasgow Comma Scale; T-RTS, Revised Trauma Score for Triage Tables 3-5 report on the injury severity measures by location of fall and by patient age.Young and middle-aged patients (≤ 60 years) who were injured by falls on streets and sidewalks were more likely to have a T-RTS score indicating the need for transport to a Trauma Center compared to young and middle-aged patients injured by falls occurring indoors.However, older patients (> 60 years) who were injured by falls indoors were more likely to have a T-RTS score indicating the need for transport to a Trauma Center than older adults who fell on streets or sidewalks.Similar patterns were observed for patients injured by falls who had moderate or severe GCS scores. 1

Table 3 Descriptive
Statistics for EMS Encounters for Reported Location of Fall Injuries by GCS, Categorized by Age.1

Table 4 Descriptive
Statistics for EMS Encounters for Reported Location of Fall Injuries by Patient Acuity, Categorized by Age.

Table 5 Descriptive
Statistics for EMS Encounters for Reported Location of Fall Injuries by Need for Triage to a Trauma Center, Categorized by Age.1