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The demand for prehospital emergency services in an aging society
PII:
Soc. Sci. Med. Vol. 46, No. 8, pp. 1027±1031, 1998 # 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain S0277-9536(97)10029-6 0277-9536/98 $19.00 + 0.00
THE DEMAND FOR PREHOSPITAL EMERGENCY SERVICES IN AN AGING SOCIETY CHARLES E. MCCONNEL1,2* and ROSEMARY W. WILSON1 Department of Gerontology and Geriatric Services, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, Texas 75235-8875, U.S.A. and 2Department of Family Practice and Community Medicine, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, Texas 75235-8875, U.S.A.
1
AbstractÐThis research examines the implications of an aging society on the demand for prehospital emergency medical services (EMS). Using a large comprehensive set of population-based EMS utilization data (N = 73 874) and population data from the 1990 Census for the City of Dallas, Texas, rates of utilization for eight age groups were computed for total EMS incidents, incidents requiring transport services, and a sub-category of transport services for individuals requiring services for life-threatening conditions. The pattern of utilization associated with age was found to be tri-modal with rates rising geometrically with age for individuals aged 65 and over. Compared to the age group 45 to 64 years of age, rates of utilization for those aged 85 years and older were 3.4 times higher (P < 0.001) for total EMS incidents, 4.5 times higher (P < 0.001) for emergency transports and 5.2 times higher (P < 0.001) for incidents of a life-threatening nature. A broad categorization of all EMS incidents by reason for requiring services indicates that the observed age-associated increase in utilization is due primarily to medical conditions rather than incidents arising from trauma. Finally, gender and racial/ethnic dierences in utilization are brie¯y considered. # 1998 Elsevier Science Ltd. All rights reserved Key wordsÐhealth services, emergency services, utilization, health service planning, aging
Over the next quarter-century the size of the elderly population is projected to increase 59%, rising from 12.7% to 16.5% of the total U.S. population (U.S. Bureau of the Census, 1996). Among the many social and economic implications associated with this rapid aging of the population, perhaps the most worrisome is the uncertainty of its impact on the nation's health care system. Most estimates of the economic impact suggest a relative shift of resources toward the elderly segment of the population, especially as it relates to the treatment and long-term care of the chronically ill (Burner et al., 1992). The literature arising from health services research is replete with studies on the age-associated patterns of health care utilization and expenditures for virtually every sector of the health economy. However, little attention has been given to establishing age-associated dierences in the demand for prehospital emergency medical services (EMS), a component of the health services system that is vital in responding to the most critical acute illness and injury episodes aecting both the elderly and other population groups (Weaver et al., 1986; McSwain, 1990; Emergency Cardiac Care Committee, 1992). For instance, it has been estimated that in the United States in 1990, of the 92 million visits to a hospital emergency department (ED) approximately *Author for correspondence.
12% required transport assistance and care from a provider of EMS (Strange et al., 1992). Research also suggests that a disproportionate amount of hospital resources is utilized by those who require the services of the EMS prior to admission to an ED (Beland et al., 1991; Stern et al., 1991). Thus for many of those who are admitted to a hospital through the emergency room following an acute episode of illness or injury, EMS is a critical ®rst link in the chain of survival (Emergency Cardiac Care Committee, 1992). While the socio-demographic and economic determinants of the demand for EMS have been of some interest to health service researchers since the 1970's, only recently have age-dierences in utilization been a major focus of research (Meador, 1991). For instance, while the early research did not explicitly examine age as an explanatory variable, when the eects of the community's age-structure were examined within an ecological framework, utilization and age were typically found to be positively related (Aldrich et al., 1971; Schuman et al., 1977; Kvalseth and Deems, 1979; Williams and Shavlik, 1979; Cadigan and Bugarin, 1989). Not until the work of Meador (1991), who explicitly considered the full-range of age-associated patterns of utilization, was it tentatively established that rates of EMS utilization were highly variable among the younger age groups through middle-age followed by substantial increases in rates of use from middle-age
1027
1028
C. E. McConnel and R. W. Wilson
through the most advanced age groups. However, in his study and other research that has focused explicitly on the age variable, the data sets have tended to be relatively small (Sosnin et al., 1989; Meador, 1991; Woord et al., 1995) or the analyses limited either in the range of ages examined (Kvalseth and Deems, 1979; Gerson and Skvarch, 1982; Strange et al., 1992; Woord et al., 1995) or by consideration of only a small sub-set of reasons for EMS utilization (Fife et al., 1984; Spaite et al., 1990). The present research extends the previous work in this area by employing a large comprehensive data set to estimate age-associated rates of utilization for the total population of a major U.S. urban area, and examines some of the mechanisms that underlie age group dierences in the utilization of EMS services.
Measures Utilization rates per 1,000 resident population were computed for each of eight age groups for total EMS incidents, and the sub-categories, transports and life-threatening incidents, the latter de®ned as the highest priorities of transport. In addition, utilization rates for each of the three categories were also computed for gender and racial/ ethnic group, classi®ed as non-Hispanic whites, African Americans, Hispanics and others. For the purpose of examining age-associated dierences in the chief complaint that initiated the use of EMS, utilization was classi®ed into two broad categories, one which identi®ed EMS responses that were initiated by strictly medically related events which did not involve trauma, such as cardiovascular or respiratory problems, and a second category identi®ed in the records as trauma related events. Analysis
METHODS
This study is based on data collected in 1990 by the Emergency Medical Services Division of the Dallas City Fire Department (DFD). By statute, the DFD is the sole provider of EMS for the residents of Dallas, Texas (pop. 1 007 000). Equipped with 22 front-line Mobile Intensive Care Units, 6 peak-demand units, 3 paramedic trucks and 22 ®rstresponder ®re engines, the DFD responded to approximately 109 000 alarms in 1990, 73 895 of which resulted in resident service incidents, i.e., alarms resulting in some form of patient contact and service provision involving an individual identi®ed as a resident of Dallas. Information on all alarms is documented in incident reports by DFD paramedics and entered into a computerized management information system for the purpose of quality assurance and planning. In the case of responses for which services are rendered, the reporting system requires a fairly comprehensive, standard account of the patient's personal characteristics, physical condition, treatment, time to scene and destination, and ®nal disposition of the case. Identi®cation and assignment of patients to one of the racial or ethnic categories, non-Hispanic white, African American, Hispanic, American Indian, Eskimo and Aleut or Asian and Paci®c-Islander, is made on the basis of some combination of language, appearance, surname, neighborhood of incident occurrence, or self-report. Information on age, race/ethnicity and gender could be ascertained for 73 874 out of the 73 895 incidents identi®ed as involving residents of Dallas. Population counts for each of the eight age groups were drawn from the 1990 census (U.S. Bureau of the Census, 1992a) and the four racial/ethnic categories were created according to procedures outlined by del Pinal (1992).
A variety of statistical analyses were performed to test hypotheses regarding age-associated trends in utilization and other socio±demographic dierences. For each of the three broad utilization categories, a chi-squared test for gradient in proportions (Fleiss, 1981) was used to test for an age-associated positive trend in utilization rates. Gender dierences in utilization were examined using a chi-squared test for dierences in proportions and dierences between the four racial/ethnic groups were examined with a Tukey-type test for multiple comparisons of proportions (Zar, 1984). Because of the large sample size, statistical tests for gender and racial/ethnic dierences were conducted at the 0.001 level of signi®cance. Age-associated trends in utilization were likewise tested at the 0.001 level of signi®cance.
RESULTS
Summary statistics for the Dallas EMS system in 1990 are presented in Table 1. Frequency and rate of utilization per 1,000 population are shown for total EMS incidents, emergency transports and transports for life-threatening events. For each of the three categories, utilization rates with respect to age are shown to be relatively high in the youngest age group and the 15±24 year old age group. Rates rise monotonically with age and continue to increase through the most advanced age group beginning with the 45±64 year old age group when total EMS incidents are considered and in the 25± 44 year old age group for the two categorizations of transport services. Arbitrarily adopting the age group 45±64 years of age as a reference group, rates of utilization for those aged 85 years and older were 3.4 times higher (P < 0.001) for total EMS incidents, 4.5 times higher (P < 0.001) for transports
Demand for prehospital emergency services
1029
Table 1. Number of prehospital emergency medical service (EMS) incidents and rates per 1,000 population by age, gender and racial/ethnic group for Dallas, Texas, 1990 Total EMS incidents Characteristics
number
rate
All ages <5 5±14 15±24 25±44 45±64 65±74 75±84 85+
73874 4645 3491 14447 27215 11264 5644 4779 2389
73.4 57.3 26.3 92.4 72.6 68.9 99.4 154.4 235.8
Male Female
35449 38425
71.6 75.1
Non-Hispanic white African American Hispanic Other
24047
50.1
39274 9740 813
132.2 47.9 25.3
Transports number Age Group 39402 1691 1432 7197 13211 6483 4052 3544 1792 Gender 18819 20583 Race/ethnicity 14114 19576 5251 461
and 5.2 times higher (P < 0.001) for incidents of a life-threatening nature. With respect to racial/ethnic dierences, for each of the three incident categories, African Americans were found to be twice as likely to require services than non-Hispanic whites and Hispanics (P < 0.001) and nearly ®ve times as likely as the ``other'' racial/ethnic groups (P < 0.001). Substantial gender dierences were also observed, with females considerably more likely than males to
Life-threatening incidents rate
number
rate
39.1 20.8 10.8 46.0 35.2 39.6 71.3 114.5 176.9
6824 306 179 987 1913 1285 928 808 418
6.8 3.8 1.3 6.3 5.1 7.9 16.3 26.1 41.3
38.0 40.2
3914 2910
7.9 5.7
29.4
2765
5.8
65.9 25.8 14.4
2998 991 70
10.1 4.9 2.3
require some form of emergency service and slightly more likely to require transport services (P < 0.001) but much less likely to require services for life-threatening conditions (5.7/1000 vs. 7.9/ 1000; P < 0.001). In an attempt to examine some of the underlying determinants of the age-associated pattern of utilization at a fairly general level of analysis, total EMS incidents were broadly classi®ed into two categories by either chief complaint or reason for utilization.
Fig. 1. EMS incidents per 1,000 population due to trauma and medical conditions by age group, Dallas, Texas, 1990.
1030
C. E. McConnel and R. W. Wilson
The ®rst category, incidents related to trauma, was constructed from the entries on the DFD individual incident reports where trauma is coded as a separate category. The second category, medically related incidents, was constructed as a residual category by subtracting from total EMS incidents all trauma related incidents and incidents identi®ed as resulting from other external causes, e.g., suicide attempts, poisonings, violent events and drownings. Figure 1 presents rates of utilization per 1,000 population for the two categories, directly standardized on the Dallas population for gender and racial/ethnic group dierences. With respect to age, rates of utilization due to trauma are shown to be tri-modal but vary in a relatively narrow range across age groups with a negative slope that was not found to be statistically signi®cant (P > 0.45). Medically related incident rates, however, while also tri-modal with respect to age, increase exponentially with age beginning in the 25±44 year old age group. For the 5±14, 15±24 and 25±44 year old age groups, there were no statistically signi®cant dierences between utilization rates due to trauma and medically related incidents; however, in the age group 85 years old and over, the rate of utilization for medically related events as the precipitating cause was four times higher than the rate of utilization due to trauma (P < 0.001). Clearly, the age-associated pattern of increasing rates of EMS utilization with age is principally due to the high prevalence of medical conditions and high incidence of acute episodes aicting the elderly population. DISCUSSION
The problems of generalizing geographically restricted urban patterns of health service provision and utilization to other areas or the nation as a whole are well known. Generalization of EMS utilization experiences in urban areas to the nation as a whole is confounded by geo-demographic variations in the relative frequency of service needs suggested by highly variable patterns in cause-speci®c mortality rates (U.S. National Center for Health Statistics, 1992). Moreover, only 31.3% of the U.S. population in 1990 was located inside central cities such as Dallas and only 77.5% in metropolitan areas (U.S. Bureau of the Census, 1992b). Nonetheless, considering the ®ndings of other geographically restricted studies, especially those that limit their focus to the age-associated utilization patterns within the elderly population (Kvalseth and Deems, 1979; Gerson and Skvarch, 1982; Strange et al., 1992; Woord et al., 1995), the present study, based on a substantially larger and more socio-demographically varied data set, extends the reach of the previous work with strong support for the view that for the population beyond middle age, the demand for EMS increases exponentially with age.
To the extent that the projections in this research represent a reasonably plausible picture of the impact of an aging society on the demand for EMS, two important implications must be addressed. First, the disproportionate increase in resources that will be required to deliver state-of-the-art prehospital emergency care suggests that municipalities and other governmental entities will be confronted with ever more dicult decisions regarding the control and subsidy of facilities and equipment. In spite of previous research indicating that investment in EMS is potentially one of the most productive public expenditures in the health care area (Schwing, 1979), the response of local governments in the past is not terribly encouraging (Stout, 1989; Smith, 1990). Moreover, local governments are likely to ®nd the eects of future demographic change especially burdensome because of the more resource intensive needs of a substantially larger number of the oldest-old residing in the community. The second issue involves the increased need for geriatric and gerontologic training of prehospital emergency personnel who will be required to treat a larger number of older and presumably sicker patients. Much like the current status of geriatrics in the medical curriculum, the incorporation of information on the unique problems of assessing and treating the elderly patient into EMS training programs has been minimal (Keller, 1992; Koin and Eie, 1992). As a consequence of the lack of emergency training oriented to problems common to the elderly patient, it is quite possible that stereotypical perceptions will unwittingly interfere with the most appropriate regime of care (Woord et al., 1993). Without a proper appreciation of gerontological and geriatric issues, decisions regarding how aggressively the severely ill elderly should be treated might be made on the basis of an informal system of rationing in accordance with concerns for cost-containment. AcknowledgementsÐThe authors gratefully acknowledge the contributions of Dr. James Atkins, Professor of Internal Medicine, UT Southwestern Medical Center at Dallas and Medical Director of the Dallas Fire Department. REFERENCES
Aldrich, C. A., Hisserich, J. C. and Lave, L. (1971) An analysis of the demand for emergency ambulance service in an urban area. American Journal of Public Health 61, 1156±1169. Beland, F., Lemay, A., Philibert, L., Maheux, B. and Gravel, G. (1991) Elderly patients' use of hospital-based emergency services. Medical Care 29, 408±418. Burner, S. T., Waldo, D. R. and McKusick, D. R. (1992) National health expenditures projections through 2030. Health Care Financing Review 14, 1±29. Cadigan, R. T. and Bugarin, C. E. (1989) Predicting the demand for emergency ambulance service. Annals of Emergency Medicine 18, 618±621.
Demand for prehospital emergency services del Pinal, J. H. (1992) Exploring alternative race±ethnic comparison groups in current population surveys. U.S. Bureau of Census, Current Population Reports, Series P23-182. U.S. Government Printing Oce, Washington, DC. Emergency Cardiac Care Committee (1992) Guidelines on cardiopulmonary resuscitation and emergency care. Part IX. Ensuring eectiveness of community-wide emergency cardiac care. Journal of the American Medical Association 288, 2289±2298. Fife, D., Barancik, J. I. and Chatterjee, B. F. (1984) Northeastern Ohio trauma study: II. Injury rates by age, sex and cause. American Journal of Public Health 74, 473±478. Fleiss, J. L. (1981) Statistical Methods for Rates and Proportions 2nd ed. John Wiley and Sons, New York. Gerson, L. W. and Skvarch, L. (1982) Emergency medical service utilization by the elderly. Annals of emergency Medicine 11, 610±612. Keller, E. H. (1992) The spectrum of prehospital care for the elderly. In Geriatric Emergency Medicine, eds. G. Bosker, G. R. Schwartz, J. S. Jones, M. Sequira, pp. 591±596. Mosby Year Book, St. Louis. Koin, D., Eie, K. (1992) Prehospital geriatric emergency care. In: Geriatric Emergency Medicine, eds. G. Bosker, G. R. Schwartz, J. S. Jones, M. Sequira, pp. 585±590. Mosby Year Book, St. Louis. Kvalseth, T. O. and Deems, J. M. (1979) Statistical models of the demand for emergency medical services in an urban area. American Journal of Public Health 69, 250± 255. McSwain, N. E. (1990) Controversies in prehospital care. In: Emergency Medicine Clinics of North America, Vol. 8, eds. W. R. Roush and P. B. Fontanarosa, pp. 145± 154. W. B. Saunders Company, Philadelphia. Meador, S. A. (1991) Age-related utilization of advanced life support services. Prehospital and Disaster Medicine 6, 9±14. Schuman, L. J., Wolfe, H. and Sepulveda, J. (1977) Estimating demands for emergency transportation. Medical Care 15, 738±749. Schwing, R. C. (1979) Longevity bene®ts and costs of reducing various risks. Technological Forecasting and Technical Change 13, 333±345. Smith, J. E. (1990) Financial considerations in emergency medical service systems. In: Emergency Medicine Clinics of North America, Vol. 8, eds. W. R. Roush and P. B. Fontanarosa, pp. 155±161. W. B. Saunders Company, Philadelphia. Sosnin, M., Young, D. and Dunt, D. R. (1989) A study of emergency ambulance utilization. Australian Family Physician 18, 233±238.
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Spaite, D. W., Criss, E. A., Valenzuela, T. D., Meislin, H. W. and Ross, J. (1990) Geriatric injury: an analysis of prehospital demographics, mechanisms and patterns. Annals of Emergency Medicine 19, 1418±1421. Stern, R. S., Weissman, J. S. and Epstein, A. M. (1991) The emergency department as a pathway to admission for poor and high-cost patients. Journal of the American Medical Association 266, 2238±2274. Stout, J. (1989) Wrestling with the big three policy issues. Journal of Emergency Medical Services 14, 79±81. Strange, G. R., Chen, E. H. and Sanders, A. B. (1992) Use of emergency departments by elderly patients: projections for a multicenter data base. Annals of Emergency Medicine 21, 819±824. U.S. Bureau of the Census (1992a) 1990 Census of the Population, General Population Characteristics, United States. U.S. Government Printing Oce, Washington, DC. U.S. Bureau of the Census (1992b) 1990 Census of Population, General Population Characteristics. Metropolitan Areas. U.S. Government Printing Oce, Washington, DC. U.S. Bureau of the Census (1996) Population Projections of the United States by age, sex, race and Hispanic origin: 1995 to 2050. Current Population Reports, series, P 25, No. 1130. U.S. Government Printing Oce, Washington, DC. U.S. National Center for Health Statistics (1992) Vital Statistics of the United States: 1989, Vol. II Ð Mortality, Part B. U.S. Government Printing Oce, Washington, DC. Weaver, W. D., Cobb, L. A., Hallstrom, A. P., Fahrenbruch, C., Copass, M. K. and Ray, R. (1986) Factors in¯uencing survival after out-of-hospital cardiac arrest. Journal of the American College of Cardiology 7, 752±757. Williams, P. M. and Shavlik, G. (1979) Geographic patterns and demographic correlates of paramedic runs in San Bernadino, 1977. Social Science and Medicine 13D, 273±279. Woord, J. L., Schwartz, E. and Byrum, J. E. (1993) The role of emergency services in health care for the elderly: a review. Journal of Emergency Medicine 11, 317±326. Woord, J. L., Moran, W. P., Heuser, M. D., Schwartz, E., Velez, R. and Mitelmark, M. B. (1995) Emergency medical transport of the elderly: a population-based study. American Journal of Emergency Medicine 13, 297±300. Zar, J. H. (1984) Biostatistical Analysis, 2nd ed. PrenticeHall, Inc., Englewood Clis, New Jersey.
Soc. Sci. Med. Vol. 46, No. 8, pp. 1027±1031, 1998 # 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain S0277-9536(97)10029-6 0277-9536/98 $19.00 + 0.00
THE DEMAND FOR PREHOSPITAL EMERGENCY SERVICES IN AN AGING SOCIETY CHARLES E. MCCONNEL1,2* and ROSEMARY W. WILSON1 Department of Gerontology and Geriatric Services, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, Texas 75235-8875, U.S.A. and 2Department of Family Practice and Community Medicine, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, Texas 75235-8875, U.S.A.
1
AbstractÐThis research examines the implications of an aging society on the demand for prehospital emergency medical services (EMS). Using a large comprehensive set of population-based EMS utilization data (N = 73 874) and population data from the 1990 Census for the City of Dallas, Texas, rates of utilization for eight age groups were computed for total EMS incidents, incidents requiring transport services, and a sub-category of transport services for individuals requiring services for life-threatening conditions. The pattern of utilization associated with age was found to be tri-modal with rates rising geometrically with age for individuals aged 65 and over. Compared to the age group 45 to 64 years of age, rates of utilization for those aged 85 years and older were 3.4 times higher (P < 0.001) for total EMS incidents, 4.5 times higher (P < 0.001) for emergency transports and 5.2 times higher (P < 0.001) for incidents of a life-threatening nature. A broad categorization of all EMS incidents by reason for requiring services indicates that the observed age-associated increase in utilization is due primarily to medical conditions rather than incidents arising from trauma. Finally, gender and racial/ethnic dierences in utilization are brie¯y considered. # 1998 Elsevier Science Ltd. All rights reserved Key wordsÐhealth services, emergency services, utilization, health service planning, aging
Over the next quarter-century the size of the elderly population is projected to increase 59%, rising from 12.7% to 16.5% of the total U.S. population (U.S. Bureau of the Census, 1996). Among the many social and economic implications associated with this rapid aging of the population, perhaps the most worrisome is the uncertainty of its impact on the nation's health care system. Most estimates of the economic impact suggest a relative shift of resources toward the elderly segment of the population, especially as it relates to the treatment and long-term care of the chronically ill (Burner et al., 1992). The literature arising from health services research is replete with studies on the age-associated patterns of health care utilization and expenditures for virtually every sector of the health economy. However, little attention has been given to establishing age-associated dierences in the demand for prehospital emergency medical services (EMS), a component of the health services system that is vital in responding to the most critical acute illness and injury episodes aecting both the elderly and other population groups (Weaver et al., 1986; McSwain, 1990; Emergency Cardiac Care Committee, 1992). For instance, it has been estimated that in the United States in 1990, of the 92 million visits to a hospital emergency department (ED) approximately *Author for correspondence.
12% required transport assistance and care from a provider of EMS (Strange et al., 1992). Research also suggests that a disproportionate amount of hospital resources is utilized by those who require the services of the EMS prior to admission to an ED (Beland et al., 1991; Stern et al., 1991). Thus for many of those who are admitted to a hospital through the emergency room following an acute episode of illness or injury, EMS is a critical ®rst link in the chain of survival (Emergency Cardiac Care Committee, 1992). While the socio-demographic and economic determinants of the demand for EMS have been of some interest to health service researchers since the 1970's, only recently have age-dierences in utilization been a major focus of research (Meador, 1991). For instance, while the early research did not explicitly examine age as an explanatory variable, when the eects of the community's age-structure were examined within an ecological framework, utilization and age were typically found to be positively related (Aldrich et al., 1971; Schuman et al., 1977; Kvalseth and Deems, 1979; Williams and Shavlik, 1979; Cadigan and Bugarin, 1989). Not until the work of Meador (1991), who explicitly considered the full-range of age-associated patterns of utilization, was it tentatively established that rates of EMS utilization were highly variable among the younger age groups through middle-age followed by substantial increases in rates of use from middle-age
1027
1028
C. E. McConnel and R. W. Wilson
through the most advanced age groups. However, in his study and other research that has focused explicitly on the age variable, the data sets have tended to be relatively small (Sosnin et al., 1989; Meador, 1991; Woord et al., 1995) or the analyses limited either in the range of ages examined (Kvalseth and Deems, 1979; Gerson and Skvarch, 1982; Strange et al., 1992; Woord et al., 1995) or by consideration of only a small sub-set of reasons for EMS utilization (Fife et al., 1984; Spaite et al., 1990). The present research extends the previous work in this area by employing a large comprehensive data set to estimate age-associated rates of utilization for the total population of a major U.S. urban area, and examines some of the mechanisms that underlie age group dierences in the utilization of EMS services.
Measures Utilization rates per 1,000 resident population were computed for each of eight age groups for total EMS incidents, and the sub-categories, transports and life-threatening incidents, the latter de®ned as the highest priorities of transport. In addition, utilization rates for each of the three categories were also computed for gender and racial/ ethnic group, classi®ed as non-Hispanic whites, African Americans, Hispanics and others. For the purpose of examining age-associated dierences in the chief complaint that initiated the use of EMS, utilization was classi®ed into two broad categories, one which identi®ed EMS responses that were initiated by strictly medically related events which did not involve trauma, such as cardiovascular or respiratory problems, and a second category identi®ed in the records as trauma related events. Analysis
METHODS
This study is based on data collected in 1990 by the Emergency Medical Services Division of the Dallas City Fire Department (DFD). By statute, the DFD is the sole provider of EMS for the residents of Dallas, Texas (pop. 1 007 000). Equipped with 22 front-line Mobile Intensive Care Units, 6 peak-demand units, 3 paramedic trucks and 22 ®rstresponder ®re engines, the DFD responded to approximately 109 000 alarms in 1990, 73 895 of which resulted in resident service incidents, i.e., alarms resulting in some form of patient contact and service provision involving an individual identi®ed as a resident of Dallas. Information on all alarms is documented in incident reports by DFD paramedics and entered into a computerized management information system for the purpose of quality assurance and planning. In the case of responses for which services are rendered, the reporting system requires a fairly comprehensive, standard account of the patient's personal characteristics, physical condition, treatment, time to scene and destination, and ®nal disposition of the case. Identi®cation and assignment of patients to one of the racial or ethnic categories, non-Hispanic white, African American, Hispanic, American Indian, Eskimo and Aleut or Asian and Paci®c-Islander, is made on the basis of some combination of language, appearance, surname, neighborhood of incident occurrence, or self-report. Information on age, race/ethnicity and gender could be ascertained for 73 874 out of the 73 895 incidents identi®ed as involving residents of Dallas. Population counts for each of the eight age groups were drawn from the 1990 census (U.S. Bureau of the Census, 1992a) and the four racial/ethnic categories were created according to procedures outlined by del Pinal (1992).
A variety of statistical analyses were performed to test hypotheses regarding age-associated trends in utilization and other socio±demographic dierences. For each of the three broad utilization categories, a chi-squared test for gradient in proportions (Fleiss, 1981) was used to test for an age-associated positive trend in utilization rates. Gender dierences in utilization were examined using a chi-squared test for dierences in proportions and dierences between the four racial/ethnic groups were examined with a Tukey-type test for multiple comparisons of proportions (Zar, 1984). Because of the large sample size, statistical tests for gender and racial/ethnic dierences were conducted at the 0.001 level of signi®cance. Age-associated trends in utilization were likewise tested at the 0.001 level of signi®cance.
RESULTS
Summary statistics for the Dallas EMS system in 1990 are presented in Table 1. Frequency and rate of utilization per 1,000 population are shown for total EMS incidents, emergency transports and transports for life-threatening events. For each of the three categories, utilization rates with respect to age are shown to be relatively high in the youngest age group and the 15±24 year old age group. Rates rise monotonically with age and continue to increase through the most advanced age group beginning with the 45±64 year old age group when total EMS incidents are considered and in the 25± 44 year old age group for the two categorizations of transport services. Arbitrarily adopting the age group 45±64 years of age as a reference group, rates of utilization for those aged 85 years and older were 3.4 times higher (P < 0.001) for total EMS incidents, 4.5 times higher (P < 0.001) for transports
Demand for prehospital emergency services
1029
Table 1. Number of prehospital emergency medical service (EMS) incidents and rates per 1,000 population by age, gender and racial/ethnic group for Dallas, Texas, 1990 Total EMS incidents Characteristics
number
rate
All ages <5 5±14 15±24 25±44 45±64 65±74 75±84 85+
73874 4645 3491 14447 27215 11264 5644 4779 2389
73.4 57.3 26.3 92.4 72.6 68.9 99.4 154.4 235.8
Male Female
35449 38425
71.6 75.1
Non-Hispanic white African American Hispanic Other
24047
50.1
39274 9740 813
132.2 47.9 25.3
Transports number Age Group 39402 1691 1432 7197 13211 6483 4052 3544 1792 Gender 18819 20583 Race/ethnicity 14114 19576 5251 461
and 5.2 times higher (P < 0.001) for incidents of a life-threatening nature. With respect to racial/ethnic dierences, for each of the three incident categories, African Americans were found to be twice as likely to require services than non-Hispanic whites and Hispanics (P < 0.001) and nearly ®ve times as likely as the ``other'' racial/ethnic groups (P < 0.001). Substantial gender dierences were also observed, with females considerably more likely than males to
Life-threatening incidents rate
number
rate
39.1 20.8 10.8 46.0 35.2 39.6 71.3 114.5 176.9
6824 306 179 987 1913 1285 928 808 418
6.8 3.8 1.3 6.3 5.1 7.9 16.3 26.1 41.3
38.0 40.2
3914 2910
7.9 5.7
29.4
2765
5.8
65.9 25.8 14.4
2998 991 70
10.1 4.9 2.3
require some form of emergency service and slightly more likely to require transport services (P < 0.001) but much less likely to require services for life-threatening conditions (5.7/1000 vs. 7.9/ 1000; P < 0.001). In an attempt to examine some of the underlying determinants of the age-associated pattern of utilization at a fairly general level of analysis, total EMS incidents were broadly classi®ed into two categories by either chief complaint or reason for utilization.
Fig. 1. EMS incidents per 1,000 population due to trauma and medical conditions by age group, Dallas, Texas, 1990.
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The ®rst category, incidents related to trauma, was constructed from the entries on the DFD individual incident reports where trauma is coded as a separate category. The second category, medically related incidents, was constructed as a residual category by subtracting from total EMS incidents all trauma related incidents and incidents identi®ed as resulting from other external causes, e.g., suicide attempts, poisonings, violent events and drownings. Figure 1 presents rates of utilization per 1,000 population for the two categories, directly standardized on the Dallas population for gender and racial/ethnic group dierences. With respect to age, rates of utilization due to trauma are shown to be tri-modal but vary in a relatively narrow range across age groups with a negative slope that was not found to be statistically signi®cant (P > 0.45). Medically related incident rates, however, while also tri-modal with respect to age, increase exponentially with age beginning in the 25±44 year old age group. For the 5±14, 15±24 and 25±44 year old age groups, there were no statistically signi®cant dierences between utilization rates due to trauma and medically related incidents; however, in the age group 85 years old and over, the rate of utilization for medically related events as the precipitating cause was four times higher than the rate of utilization due to trauma (P < 0.001). Clearly, the age-associated pattern of increasing rates of EMS utilization with age is principally due to the high prevalence of medical conditions and high incidence of acute episodes aicting the elderly population. DISCUSSION
The problems of generalizing geographically restricted urban patterns of health service provision and utilization to other areas or the nation as a whole are well known. Generalization of EMS utilization experiences in urban areas to the nation as a whole is confounded by geo-demographic variations in the relative frequency of service needs suggested by highly variable patterns in cause-speci®c mortality rates (U.S. National Center for Health Statistics, 1992). Moreover, only 31.3% of the U.S. population in 1990 was located inside central cities such as Dallas and only 77.5% in metropolitan areas (U.S. Bureau of the Census, 1992b). Nonetheless, considering the ®ndings of other geographically restricted studies, especially those that limit their focus to the age-associated utilization patterns within the elderly population (Kvalseth and Deems, 1979; Gerson and Skvarch, 1982; Strange et al., 1992; Woord et al., 1995), the present study, based on a substantially larger and more socio-demographically varied data set, extends the reach of the previous work with strong support for the view that for the population beyond middle age, the demand for EMS increases exponentially with age.
To the extent that the projections in this research represent a reasonably plausible picture of the impact of an aging society on the demand for EMS, two important implications must be addressed. First, the disproportionate increase in resources that will be required to deliver state-of-the-art prehospital emergency care suggests that municipalities and other governmental entities will be confronted with ever more dicult decisions regarding the control and subsidy of facilities and equipment. In spite of previous research indicating that investment in EMS is potentially one of the most productive public expenditures in the health care area (Schwing, 1979), the response of local governments in the past is not terribly encouraging (Stout, 1989; Smith, 1990). Moreover, local governments are likely to ®nd the eects of future demographic change especially burdensome because of the more resource intensive needs of a substantially larger number of the oldest-old residing in the community. The second issue involves the increased need for geriatric and gerontologic training of prehospital emergency personnel who will be required to treat a larger number of older and presumably sicker patients. Much like the current status of geriatrics in the medical curriculum, the incorporation of information on the unique problems of assessing and treating the elderly patient into EMS training programs has been minimal (Keller, 1992; Koin and Eie, 1992). As a consequence of the lack of emergency training oriented to problems common to the elderly patient, it is quite possible that stereotypical perceptions will unwittingly interfere with the most appropriate regime of care (Woord et al., 1993). Without a proper appreciation of gerontological and geriatric issues, decisions regarding how aggressively the severely ill elderly should be treated might be made on the basis of an informal system of rationing in accordance with concerns for cost-containment. AcknowledgementsÐThe authors gratefully acknowledge the contributions of Dr. James Atkins, Professor of Internal Medicine, UT Southwestern Medical Center at Dallas and Medical Director of the Dallas Fire Department. REFERENCES
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