Trends in Infectious Disease Hospitalizations Among American ... - NCBI

Trends in Infectious Disease Hospitalizations Among American Indians and Alaska Natives

A B S T R A C T Objectives. This study sought to describe trends in hospitalizations associated with infectious diseases among American Indians and Alaska Natives. Methods. Infectious disease hospitalizations and rates among American Indians and Alaska Natives from 1980 through 1994 were examined via Indian Health Service hospital discharge data and compared with published trends for the general US population. Results. Annual hospitalization rates for infectious diseases among American Indians and Alaska Natives decreased by 31.0% between 1980 and 1994. Infectious disease hospitalizations accounted for 16.3% of all hospitalizations in 1980 and 21.2% in 1994, an increase of 30.1%. In 1994, the age-adjusted infectious disease hospitalization rate for American Indians and Alaska Natives was 1863 per 100 000 population, approximately 21% greater than that for the general US population. Conclusions. Hospitalization trends for infectious diseases show that there has been improvement in the health status of American Indians and Alaska Natives but also indicate that this population has a higher infectious disease burden than the general US population. (Am J Public Health. 2001;91:425–431)

March 2001, Vol. 91, No. 3

Robert C. Holman, MS, Aaron T. Curns, MPH, Stephen F. Kaufman, MS, James E. Cheek, MD, MPH, Robert W. Pinner, MD, and Lawrence B. Schonberger, MD, MPH Historically, infectious diseases have adversely affected the health and life expectancy of American Indians and Alaska Natives.1 Despite a decline in infectious disease mortality among American Indians and Alaska Natives over the past several decades, this population continues to have higher risks for infectious disease mortality than other groups.1–4 In most categories of infectious diseases, mortality rates are higher for American Indians and Alaska Natives than for the general US population.2,5 Overall, infectious diseases are the third leading cause of death in the United States.6 Infectious disease mortality within the United States declined markedly during the 20th century, largely because of improved medical care and successful public health interventions. Nevertheless, year-to-year variability and recent increases in deaths attributable to infectious disease have been documented.7,8 A recent study of hospitalizations in the United States from 1980 through 1994 reported that increasing proportions of hospitalizations were due to infectious diseases, even though overall hospitalization rates had declined.9 However, this study did not include hospitalizations among American Indians and Alaska Natives reported through the Indian Health Service (IHS),10 an agency of the US Department of Health and Human Services that provides comprehensive health services to American Indian and Alaska Native populations and maintains records of these services.5 Approximately 1.4 million American Indians and Alaska Natives, about 60% of all American Indians and Alaska Natives, are eligible for medical care from the IHS, which operates and provides funds for a network of inpatient and ambulatory care facilities across the continental United States and Alaska.5,11 To assess the impact of infectious diseases on this population, we examined infectious disease hospitalizations among Ameri-

can Indians and Alaska Natives who had received IHS-reported medical care from 1980 through 1994. We also compared infectious disease trends and annual rates with those for the general US population during the same period.

Methods Hospital discharges reported to the IHS for calendar years 1980 through 1994 were obtained from IHS hospital discharge data.12 The hospital discharge data maintained by the IHS consist of patient discharge records obtained from IHS-operated and tribally operated hospitals and hospitals that have contracted with the IHS or tribes to provide health care services to federally recognized American Indians and Alaska Natives within the United States.5 Of the 12 IHS administrative areas, 10 were included in this study.The California and Portland areas were excluded, because no IHS or tribally operated hospitals are located in these areas and they either do not report contract health service inpatient data by diagnosis (California) Robert C. Holman, Aaron T. Curns, and Lawrence B. Schonberger are with the Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Ga. Stephen F. Kaufman is with the Indian Health Service, Rockville, Md. James E. Cheek is with the Epidemiology Program, Office of Public Health, Indian Health Service, Albuquerque, NM. Robert W. Pinner is with the National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Ga. Requests for reprints should be sent to Robert C. Holman, MS, Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, MS A39, Atlanta, GA 30333. This article was accepted May 20, 2000. Note. The opinions expressed in this article do not necessarily reflect the views of the Indian Health Service.

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or have limited contract health service funds for inpatient care (Portland).13,14 We selected all IHS hospital discharge records with an infectious disease listed as a diagnosis, using a previously described infectious disease classification method9,15 based on the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM).16 Two diagnoses (septic myocarditis and infected abrasion or friction burn [ICD-9-CM codes 422.92 and 910.1, respectively]) were added to the “other infectious diseases” group. Hospitalizations involving a first-listed diagnosis of an infectious disease were analyzed unless otherwise indicated. Hospitalizations with “any-listed” infectious disease were defined as hospitalizations in which an infectious disease diagnosis was listed as any one of the 6 or fewer diagnoses on the IHS patient record. Hospital stays for newborns were excluded. IHS hospital discharge records were examined by age group, sex, geographic region, and infectious disease category. Regions for the IHS areas were defined as follows: East (Nashville), Northern Plains (Aberdeen, Bemidji, and Billings), Alaska, Oklahoma, and Southwest (Albuquerque, Navajo, Phoenix, and Tucson).13 Hospital lengths of stay were compared via the Wilcoxon rank sum test.17 Annual hospitalization rates for American Indians and Alaska Natives were calculated as the number of hospitalizations per 100 000 population. Annual rates were cal-

culated for all causes, first-listed infectious diseases, any-listed infectious diseases, and specific infectious disease group hospitalizations. Risk ratios (RRs) and 95% confidence intervals (CIs) were calculated. Annual hospital fatality rates were also calculated for rate comparisons. We determined yearly population denominators for IHS hospitalizations by using 1996 IHS user population estimates and adjusting for annual changes in the IHS service population (based on March 1997 area estimates), excluding the California and Portland areas.5 The 1996 user population included all registered American Indians and Alaska Natives who resided in an IHS area and had received care in the IHS system during the previous 3 years. The service population was an estimate of the number of American Indians and Alaska Natives eligible for IHS services. We calculated age-adjusted 1994 infectious disease and total hospitalization rates among American Indians and Alaska Natives by the direct method, using the 1994 postcensus population of the United States.18 We compared infectious disease hospitalization trends and rates for American Indians and Alaska Natives with those of the general US population by using previously published estimates for 1980 through 1994.9 In addition, we calculated 1994 US rates and 95% confidence intervals to determine significant differences between American Indian/Alaska Native rates and US rates.10,19

Results Overall Trends From 1980 through 1994, 248 072 firstlisted infectious disease hospitalizations among American Indians and Alaska Natives were reported to the IHS. The annual hospitalization rate for infectious diseases declined from 2338 (1980) to 1613 (1994) per 100000 population, a 31.0% decrease (Table 1 and Figure 1). The total hospitalization rate declined 47.1%, from 14 371 to 7603 per 100 000 population (Table 2). Infectious disease hospitalizations accounted for 16.3% of all hospitalizations in 1980 and 21.2% in 1994, a 30.1% increase; any-listed infectious disease hospitalizations increased by 36.6% (from 23.2% to 31.7%). The infectious disease hospitalization trend for American Indians and Alaska Natives showed a steeper decline than that for the general US population, but the increase in the proportion of hospitalizations attributable to infectious diseases was greater.9 In 1994, the percentage of infectious disease hospitalizations among American Indians and Alaska Natives was 21.2%, as compared with 12% (SD = 0.2%) for the general US population.

Age, Sex, and Region Hospitalization trends for infectious diseases among American Indians and Alaska Natives differed by age group (Table 1 and

TABLE 1—Characteristics of American Indian/Alaska Native Infectious Disease Hospitalizations: Indian Health Service, 1980 and 1994 1980 Characteristic Sex Male Female Age, y