- Email: [email protected]
Asthma prevalence among Alaska Native and nonnative residents younger than 20 years enrolled in Medicaid
Asthma prevalence among Alaska Native and nonnative residents younger than 20 years enrolled in Medicaid Bradford D. Gessner, MD, MPH
Background: No study of childhood asthma prevalence in Alaska or among Alaska Natives has been conducted. Objective: To determine asthma prevalence among Alaska Medicaid enrollees younger than 20 years, with an emphasis on Alaska Natives, the state’s largest minority and predominant rural citizens. Methods: A master database was obtained that included all children enrolled in Medicaid during July 1998 through June 1999. Physician, pharmacy, and hospital claims files for International Classification of Diseases codes 493.0x to 493.9x were linked to this master database. Asthma was defined as any asthma-related care or medication claim. Results: Asthma prevalence among the study population was 6.9%. Alaska Natives had a lower asthma prevalence than nonnatives (risk ratio [RR], 0.70; 95% confidence interval [CI], 0.66 – 0.75), but among the subgroup of children residing in the state’s major urban center, Alaska Natives had a higher prevalence. Overall, 0.22% of the study population experienced an asthma-related hospitalization, with Alaska Natives having a higher risk of hospitalization than nonnatives (RR, 1.6; 95% CI, 1.2–2.3). Among hospitalized children, Alaska Natives were less likely to have received a long-term control medication (RR, 0.54; 95% CI, 0.33– 0.88). Conclusions: Compared with nonnatives, Alaska Natives have a lower risk of asthma but only among nonurban residents. The increased risk of hospitalization among Alaska Natives may be related to underuse of long-term control medications. Ann Allergy Asthma Immunol. 2003;90:616– 621.
INTRODUCTION Asthma is one of the leading causes of childhood morbidity in the developed world and the most common chronic childhood disease in the United States.1,2 Furthermore, asthma prevalence appears to be increasing.3– 6 Although previous studies have evaluated asthma prevalence among minority populations,7–10 no evaluation has yet examined asthma among Alaska Natives. The current study was undertaken to evaluate asthma prevalence and asthma-related hospitalizations among Alaska Natives and nonnatives younger than 20 years who were enrolled in Medicaid during 1998 to 1999. Secondary evaluations examined the demographic risk factors for asthma and prevalence of long-term control medication use. METHODS Health Care in Alaska During the study period, health care services in Alaska were delivered through a variety of private, public, nonprofit, Native Corporation, and Indian Health Service entities. Alaska Natives constituted the state’s largest racial minority and predominant rural residents and usually received services through Native Corporation and Indian Health Service facilities. For Medicaid-enrolled persons, all in-state facilities
Alaska Division of Public Health, Anchorage, Alaska. Received for publication November 9, 2002. Accepted for publication in revised form March 8, 2002.
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billed Medicaid regardless of where a specific individual obtained care. During the last 4 months of the study period, Alaska had in place Denali KidCare, the state’s Child Health Insurance Program that extended Medicaid coverage to all children younger than 19 years, including Indian Health Service and Native Corporation beneficiaries, at 200% of the federal poverty level. Data Source Multiple data files were obtained from the Alaska Division of Medical Assistance. The master file consisted of all persons younger than 20 years enrolled in Medicaid from July 1, 1998, through June 30, 1999. We could not use earlier data because until 1998 the Indian Health Service submitted Medicaid billing in batches, thus preventing analysis of outcomes by individual. The master file contained a unique identifier for each person and the person’s town or village of residence, race, sex, and date of birth. Not all children were enrolled in Medicaid for the entire study period, either because they lost their eligibility or enrolled after the beginning of the study. Among all children, 38% were continuously enrolled during the entire study period compared with 56% of children with asthma. Among children not continuously enrolled, the average length of enrollment was 5.7 months for all children and 7.6 months for children with asthma. Four files were obtained that contained all provider, inpatient facility, and outpatient hospital claims for International Classification of Diseases, Ninth Revision (ICD-9) codes 493.0x to 493.9x, the standard codes for asthma. A fifth
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subsidiary file was obtained for pharmacy claims paid by Medicaid. This file was limited to approved claims for the following medications manufactured by any company: oral or intravenous theophylline, inhaled or liquid albuterol, and inhaled bitolterol, pirbuterol, salmeterol, beclomethasone, triamcinolone, flunisolide, fluticasone, budesonide, cromolyn, nedocromil, zileuton, zafirlukast, montelukast, and ipratropium bromide. Cromolyn, nedocromil, salmeterol, leukotriene modifiers, methylxanthines, and inhaled steroids were classified as long-term control medications, whereas shortacting inhaled and oral -agonists and ipratropium bromide were classified as quick-relief medications. The pharmacy file had information on filled prescriptions, which reflects a combination of provider prescribing practices and patient prescription filling practices. These five files contained one record for each billing episode. Consequently, individuals might have had more than one record in any one file. Furthermore, these files did not describe mutually exclusive visits, since billing at some facilities included physician fees, whereas at other facilities physicians billed separately. Records for claims that were submitted but denied by Medicaid, usually because an individual was not enrolled at the time the service was provided, were not included in analysis. Case Definitions Asthma was defined as an approved claim for asthma-related medication use or care. Within this group, subgroups were also evaluated, including persons with approved claims for both medication and care and persons with approved claims for asthma-related inpatient care. Persons with asthma who did not receive an ICD-9 code for asthma or an asthmarelated medication during the study year were excluded from this case definition. Analysis The 1 pharmacy and 4 services-related data files were linked to the eligibility file by matching on the unique identifier number. Because asthma prevalence was the primary outcome of interest, all analyses were performed with the individual as the unit of analysis. Consequently, multiple visits or medications for a single person during the study year were ignored. Four major risk factors were available for analysis in the Medicaid database: sex, Alaska Native status, age, and census area of residence. Residence was categorized as Anchorage or non-Anchorage; Anchorage was the only substantial urban center and contained approximately half of the state’s population and 3 of its 4 largest hospitals. Recent data indicate that a substantial proportion of children may benefit from long-term control medication and particularly inhaled steroid use.11 Consequently, a separate analysis was conducted examining medication use. Because not all children with asthma necessarily had a medical indication for long-term control medications, this analysis concentrated on children with an asthma-related hospitalization.
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During univariate analysis, risk ratios and 95% confidence intervals (CIs) were calculated. Multiple logistic regression models were created to evaluate the independent association between outcome variables and Alaska Native status, age, sex, and census area of residence. For all models, all independent variables were entered simultaneously. All analyses were performed with SPSS version 10 statistical software (SPSS Inc, Chicago, IL). RESULTS Univariate Claims Prevalence and Identification of Risk Groups During the 1-year study period, 59,501 in-state residents younger than 20 years were enrolled in Medicaid and 4131 had one or more claims for asthma-related care or medication. The overall asthma prevalence was 6.9%; 6.1% of children received asthma-related medication, 3.2% received asthma-related care, 2.3% received both medication and care, and 0.22% had an asthma-related hospitalization. Among all children with asthma, 3.1% had one or more hospitalizations. The number of children with a first claim for asthma during the study period increased from 839 during the first 4 months of the study to 1,149 and 2,092 during the second and third 4 months of the study, respectively (for some children, the exact date of the first claim was not known). The proportion of children who experienced one of the measured outcomes was higher in males than females, children younger than 5 years than older persons, and persons living in the Anchorage census area than those living in less populated areas (Table 1). Compared with nonnatives, the overall asthma prevalence was lower among Alaska Natives, but the proportion who were hospitalized was higher. Among different census areas (Alaska does not have counties), overall asthma prevalence varied from 0 to 9.8%. The south central and southeast regions of Alaska, where most of the state’s population resided during the study period, had the highest prevalences. In the three most populous census areas, Alaska Natives had asthma prevalences of 11, 8.6, and 10% (in descending order of population) compared with 9.4, 7.2, and 7.9% for nonnatives. In less populous census areas, there was more variation between Alaska Native and nonnative asthma prevalences; much of this variation, however, might be attributed to the small number of cases at this level of stratification. Multivariate Risk Factor Analysis Sex, Alaska Native status, age, and Anchorage residence were all entered simultaneously into a multiple logistic regression model for each of the outcomes of interest. Similar to univariate analyses, male sex, nonnative status, age younger than 5 years, and living in the Anchorage census area were associated with overall asthma prevalence (Table 2). Male sex, Alaska Native status, and age younger than 5 years were risk factors for hospital care. In Alaska, Alaska Natives live predominantly in rural areas and nonnatives live predominantly in urban areas; Anchorage
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Table 1. Medicaid-Enrolled Alaska In-State Residents Younger than 20 Years who Experienced Various Asthma Outcomes, July 1998 through June 1999
Risk group
Race Alaska Native (n ⫽ 23,318) Nonnative (n ⫽ 36,183) Sex Male (n ⫽ 29,991) Female (n ⫽ 29,510) Age group, y 0–4 (n ⫽ 19,977) 5–9 (n ⫽ 16,811) 10–14 (n ⫽ 13,176) 15–19 (n ⫽ 9537) Census area of residence Anchorage (n ⫽ 19,250) Non-Anchorage (n ⫽ 40,251)
Asthma-related medication or care
Asthma-related medication and care
Asthma-related hospitalization
Residents, %
RR (95% CI)
Residents, %
RR (95% CI)
Residents, %
RR (95% CI)
5.5 7.9
0.70 (0.66–0.75) Referent
1.4 2.9
0.46 (0.41–0.53) Referent
0.28 0.17
1.6 (1.2–2.3) Referent
7.5 6.3
1.2 (1.1–1.3) Referent
2.6 2.0
1.3 (1.2–1.5) Referent
0.26 0.18
1.5 (1.0–2.1) Referent
10 5.1 5.2 5.4
1.9 (1.7–2.1) 0.95 (0.85–1.1) 0.97 (0.87–1.1) Referent
3.2 2.0 2.1 1.6
2.0 (1.7–2.4) 1.3 (1.0–1.5) 1.4 (1.1–1.6) Referent
0.40 0.12 0.10 0.17
2.4 (1.4–4.1) 0.71 (0.37–1.4) 0.59 (0.28–1.2) Referent
10 5.5
1.8 (1.7–1.9) Referent
3.2 1.9
1.7 (1.5–1.9) Referent
0.21 0.22
0.94 (0.65–1.4) Referent
Abbreviations: CI, confidence interval; RR, risk ratio.
is the largest city and center for medical care in the state. To more clearly illustrate the risk of asthma associated with Alaska Native status independent of residence, data were stratified into Anchorage and non-Anchorage residence. Then multiple logistic regression analyses were performed with Alaska Native status, male sex, and age younger than 5 years entered simultaneously. Compared with nonnatives, Alaska Native status was associated with an increased odds of asthma among Anchorage residents (odds ratio [OR], 1.2; 95% CI, 1.1–1.3) but a decreased odds of asthma among non-Anchorage residents (OR, 0.65; 95% CI, 0.59 – 0.71). A similar analysis was performed for hospitalizations. Alaska Native status was associated with an increased odds of asthma-related hospitalization among both Anchorage (OR, 2.5; 95% CI, 1.3– 4.7) and non-Anchorage (OR, 1.5; 95% CI, 0.95–2.2) residents. Differences between populations in the proportion of children hospitalized for asthma may reflect differences in the proportion of children with asthma who become hospitalized or differences in the underlying asthma prevalence. To distinguish between these possibilities, the final set of multivariate analyses determined the proportion of children who had
1 or more hospitalizations among the subgroup of children with asthma. Among the subgroup of children with asthma (and similar to results for the entire population of Medicaideligible children), Alaska Native status was associated with an increased odds of asthma-related hospitalization among both Anchorage (OR, 2.2; 95% CI, 1.2– 4.2) and non-Anchorage residents (OR, 2.0; 95% CI, 1.3–3.1). Medication Use Among the 4,131 children with asthma, 86% received at least one quick-relief medication, 18% received at least one longterm control medication, and 10% received at least one inhaled steroid. Among the subgroup of 1,262 children who received both medication and care, 36% received a long-term control medication and 21% received an inhaled steroid. Among the subgroup of 129 hospitalized children, 36% received a long-term control medication and 23% received an inhaled steroid. Among hospitalized children, Alaska Natives, children younger than 5 years, and non-Anchorage residents were less likely than nonnatives, older children, and Anchorage residents to have received long-term control medications or inhaled steroids (Table 3).
Table 2. Multiple Logistic Regression Analysis for Various Asthma Outcomes among Medicaid-Enrolled Alaska In-State Residents Younger than 20 Years, July 1998 through June 1999 OR (95% CI) Risk group
Alaska Native Male Age ⬍5 y Anchorage resident
Asthma-related medication or care
Asthma-related medication and care
Asthma-related hospitalization
0.81 (0.75–0.87) 1.2 (1.1–1.3) 2.0 (1.9–2.2) 1.8 (1.7–1.9)
0.51 (0.45–0.58) 1.3 (1.2–1.5) 1.6 (1.5–1.8) 1.5 (1.3–1.6)
1.7 (1.2–2.4) 1.4 (1.0–2.0) 3.3 (2.3–4.7) 1.1 (0.71–1.5)
Abbreviations: CI, confidence interval; OR, odds ratio.
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Table 3. Medicaid-Enrolled Alaska In-State Residents Younger than 20 Years who Had Been Hospitalized for Asthma and who Received Any Long-term Control Medication or Inhaled Steroids Alone, July 1998 through June 1999 Long-term medication*
Inhaled steroid
Risk group Race Alaska Native Nonnative Sex Male Female Age group, y 0–4 5–9 10–14 15–19 Census area of residence Anchorage Non-Anchorage
Residents, %
RR (95% CI)
Residents, %
RR (95% CI)
26 48
0.54 (0.33–0.88) Referent
17 29
0.58 (0.30–1.1) Referent
34 40
0.84 (0.53–1.3) Referent
17 31
0.55 (0.29–1.0) Referent
26 55 62 44
0.60 (0.31–1.2) 1.3 (0.64–2.5) 1.4 (0.70–2.8) Referent
11 40 46 38
0.30 (0.12–0.73) 1.1 (0.47–2.4) 1.2 (0.52–2.9) Referent
44 33
1.4 (0.86–2.1) Referent
35 16
2.1 (1.1–4.0) Referent
Abbreviations: CI, confidence interval; RR, risk ratio. * Long-term medications included inhaled steroids, methylxanthines, cromolyn, nedocromil, salmeterol, and leukotriene modifiers.
Inhaled steroid use was examined in more detail. Of the 426 children who filled a prescription for inhaled steroids, 254 (60%) filled a single prescription (range of filled prescriptions, 1–13; median, 2). To determine if children appropriately refilled inhaled steroid prescriptions, the interval between refills was examined for the 172 children who filled at least two prescriptions. For all children, the median length of time between refills was 45 days, with 28% of refills occurring within 30 days and 62% occurring within 60 days. No difference existed between Alaska Natives and nonnatives in the median length of time between prescription refills. DISCUSSION Among the Alaska Medicaid-enrolled population younger than 20 years, asthma prevalence was 6.9% and 0.22% were hospitalized with asthma. Comparisons with other studies are problematic because of differing methods, particularly the case definition of asthma. Several similar studies12–14 of Medicaid populations suggest that overall asthma prevalence in other states is 1.5 to 2 times higher than in Alaska. The occurrence of hospitalization for asthma in Alaska is lower than in Michigan,3 comparable to Connecticut,14 and higher than in Nebraska.13 This is the first study, to our knowledge, to examine Alaska Native asthma prevalence. Overall, Alaska Natives had a lower asthma prevalence than nonnatives; stratified analysis, however, showed that this difference existed only for residents living outside Alaska’s major urban center. Among nonurban residents, Alaska Natives tend to live in smaller communities and to have lived for a longer period in those communities than nonnatives. Consequently, nonurban Natives may have received less exposure than nonnatives to whatever factors have led to the documented increase in asthma prevalence in more urban communities.4,7,8,15,16 In
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rural Alaska, an extensive system of Native Corporation and Indian Health Service health care facilities provides free care to Alaska Natives, whereas no similar health insurance system exists for nonnatives; thus, it is unlikely that poor access to care and underreporting explain the low asthma prevalence among nonurban Alaska Natives. The relatively high risk of asthma among urban Alaska Natives suggests that previously reported genetic differences17,18 also do not explain the observed racial differences in asthma prevalence. Independent of residence in Alaska’s urban center, Alaska Natives with asthma were more likely to have an asthmarelated hospitalization than nonnatives. Some other studies3,16,19 have also found that minority populations are more likely to be hospitalized for asthma, whereas at least one study20 found that American Indians and Alaska Natives grouped together do not have an increased risk of hospitalization. Several potential reasons exist for the findings from the current study. Because provision of care in Alaska is largely stratified by Alaska Native status, differences in therapeutic strategies between care providers might contribute to different hospitalization rates. The only therapy-related outcome available for measurement, long-term control medication use, provided some support for this hypothesis, since hospitalized Alaska Natives were significantly less likely than nonnatives to have received a long-term control medication, including inhaled steroids. Alaska Native children have some of the highest respiratory syncytial virus and pneumococcal pneumonia incidences ever reported.21,22 Although early exposure to environmental toxins may decrease the risk of developing asthma,18 respiratory infections may increase the risk of hospitalizations among children who have asthma.23 Alternatively, the results may reflect a variety of biases, including differences among providers with respect to
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assigning a diagnosis of asthma and differences in provider or self-referral patterns for hospitalization. Long-term control medications, particularly inhaled corticosteroids, have become the accepted standard for ongoing management of persistent asthma.11 Use of these medications in the current study population, however, was low, particularly among high-risk children. Although some subpopulations were particularly unlikely to have received long-term control medications, such as Alaska Natives and younger children, long-term control medication use was low among all groups evaluated, a finding documented in other populations as well.24 This result may reflect either failure of providers to prescribe long-term control medications or failure of patients to fill prescriptions. Among children who used inhaled steroids, 40% had an elapsed time between prescription refills of more than 60 days, the maximum length of time a standard 120-dose inhaler would last assuming continuous twice-daily use. These results suggest the need for intervention programs to increase the use of steroid and other longterm control medications, including education programs, improving patient-physician interactions, implementation of National Asthma Education and Prevention Program guidelines for the diagnosis and management of asthma (www. nhlbi.nih.gov/about/naepp/), and possibly provider home visitations for children with more severe asthma. The current study has several limitations. It relies on Medicaid claims data rather than parent or patient surveys as has been performed for the most recent studies of asthma prevalence.25 It also relies on ICD-9 coding, which is unlikely to identify all cases of asthma. For both of these reasons, asthma prevalence, particularly for mild cases, may have been underestimated. Alternatively, we may have overestimated asthma prevalence by including oral -agonist medications, particularly among younger children who may receive these medications for upper respiratory tract illnesses. The data set was restricted to children enrolled in Medicaid during the study year, and these children may have different asthma prevalences than the remaining population of Alaska children.26 Finally, the short study period precluded evaluation of temporal trends. Compared with nonnatives, rural Alaska Native children had a low asthma prevalence, whereas urban Alaska Natives had a high prevalence. Further evaluation of the reasons for this finding may shed light on the mechanisms associated with the recent increase in asthma prevalence throughout the United States. Alaska Natives had a relatively high risk of asthma-related hospitalization, possibly due to underuse of long-term control medications. Although long-term control medication use was low among all populations, intervention programs to improve medication use and adherence27 targeted toward Alaska Natives and their care providers may help decrease the excess hospitalization seen among this population. The ongoing use of the Medicaid database for surveillance could help determine if Alaska is meeting Healthy People 2010 goals for reductions in asthma morbidity, particularly asthma-related hospitalizations.
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REFERENCES 1. Sears MR. Epidemiology of childhood asthma. Lancet. 1997; 350:1015–1020. 2. Newacheck PW, Taylor WR. Childhood chronic illness: prevalence, severity, and impact. Am J Public Health. 1992;82: 364 –371. 3. Gerstman BB, Bosco LA, Tomita DK. Trends in the prevalence of asthma hospitalization in the 5- to 14-year-old Michigan Medicaid population, 1980 to 1986. J Allergy Clin Immunol. 1993;91:838 – 843. 4. Gergen PF, Mullally DI, Evans R. National survey of prevalence of asthma among children in the United States, 1976 to 1980. Pediatrics. 1988;81:1–7. 5. Centers for Disease Control and Prevention. Measuring childhood asthma prevalence before and after the 1997 redesign of the National Health Interview Survey—United States. MMWR Morb Mortal Wkly Rep. 2000;49:908 –911. 6. Farber HJ, Wattigney W, Berenson G. Trends in asthma prevalence: the Bogalusa heart study. Ann Allergy Asthma Immunol. 1997;78:265–269. 7. Aligne CA, Auinger P, Byrd RS, Weitzman M. Risk factors for pediatric asthma: contributions of poverty, race, and urban residence. Am J Respir Crit Care Med. 2000;162:873– 877. 8. Litonjua AA, Carey VJ, Weiss ST, Gold DR. Race, socioeconomic factors, and area of residence are associated with asthma prevalence. Pediatr Pulmonol. 1999;28:394 – 401. 9. Miller JE. The effects of race/ethnicity and income on early childhood asthma prevalence and health care use. Am J Public Health. 2000;90:428 – 430. 10. Crain EF, Weiss KB, Bijur PE, Hersh M, Westbrook L, Stein RE. An estimate of the prevalence of asthma and wheezing among inner-city children. Pediatrics. 1994;94:356 –362. 11. National Heart, Lung, and Blood Institute, National Institutes of Health. Guidelines for the Diagnosis and Management of Asthma. Bethesda, MD: National Institutes of Health; July 1997. NIH publication 97– 4051. 12. Buescher PA, Jones-Vessey K. Using Medicaid data to estimate state- and county-level prevalence of asthma among lowincome children. Matern Child Health J. 1999;3:211–216. 13. Nelson RP, Raymond RA, Leopold R, et al. Asthma in Nebraska 1987–98: Nebraska Epidemiology Report. Lincoln, NE: Office of Epidemiology, Nebraska Health and Human Services System; March 2001. 14. Rowland JG, Garcia J. Asthma in Connecticut. Hartford, CT: Connecticut Dept of Public Health; May 2001. 15. Hartert TV, Peebles RS. Epidemiology of asthma: the year in review. Opin Pulm Med. 2000;6:4 –9. 16. Patino CM, Martinez FD. Interactions between genes and environment in the development of asthma. Allergy. 2001;56: 279 –286. 17. Cantani A. The growing genetic links and the early onset of atopic diseases in children stress the unique role of the atopic march: a meta-analysis. J Invest Allergol Clin Immunol. 1999; 9:314 –320. 18. Sandford A, Weir T, Pare P. The genetics of asthma. Am J Respir Crit Care Med. 1996;153:1749 –1765. 19. Liu LL, Stout JW, Sullivan M, Solet D, Shay DK, Grossman DC. Asthma and bronchiolitis hospitalizations among American Indian children. Arch Pediatr Adolesc Med. 2000;154:991–996.
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20. Hisnanick JJ, Coddington DA, Gergen PJ. Trends in asthmarelated admissions among American Indian and Alaskan native children from 1979 to 1989: universal health care in the face of poverty. Arch Pediatr Adolesc Med. 1994;148:357–363. 21. Karron RA, Singleton RJ, Bulkow L, Parkinson A, Kruse D, et al. Severe respiratory syncytial virus disease in Alaska native children. RSV Alaska Study Group. J Infect Dis. 1999;180: 41– 49. 22. Davidson M, Parkinson AJ, Bulkow LR, Fitzgerald MA, Peters HV, Parks DJ. The epidemiology of invasive pneumococcal disease in Alaska, 1986 –1990: ethnic differences and opportunities for prevention. J Infect Dis. 1994;170:368 –376. 23. Glezen WP, Greenberg SB, Atmar RL, Piedra PA, Couch RB. Impact of respiratory virus infections on persons with chronic underlying conditions. J Am Med Assoc. 2000;283:499 –505. 24. Donahue JG, Fuhlbrigge AL, Finkelstein JA, Fagan JA, Livingston JM, et al. The Pediatric Asthma Care Patient Outcomes Research Team. Asthma pharmacotherapy and utilization by children in 3 managed care organizations. J Allergy Clin Immunol. 2000;6:1108 –1114.
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25. Asher MI, Keil U, Anderson HR, Beasley R, Crane J, et al. International Study of Asthma and Allergies in Childhood (ISAAC): rationale and methods. Eur Respir J. 1995;8: 483– 491. 26. Finkelstein JA, Barton MB, Donahue JG, Algatt-Bergstrom P, Markson LE, Platt R. Comparing asthma care for Medicaid and non-Medicaid children in a health maintenance organization. Arch Pediatr Adolesc Med. 2000;154:563–568. 27. Fish L, Lung CL, The Antileukotriene Working Group. Adherence to asthma therapy. Ann Allergy Asthma Immunol. 2001; 86:24 –30. Requests for reprints should be addressed to: Bradford D. Gessner, MD, MPH Alaska Division of Public Health 3601 C St PO Box 240249 Anchorage, AL 99524 E-mail: [email protected]
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Background: No study of childhood asthma prevalence in Alaska or among Alaska Natives has been conducted. Objective: To determine asthma prevalence among Alaska Medicaid enrollees younger than 20 years, with an emphasis on Alaska Natives, the state’s largest minority and predominant rural citizens. Methods: A master database was obtained that included all children enrolled in Medicaid during July 1998 through June 1999. Physician, pharmacy, and hospital claims files for International Classification of Diseases codes 493.0x to 493.9x were linked to this master database. Asthma was defined as any asthma-related care or medication claim. Results: Asthma prevalence among the study population was 6.9%. Alaska Natives had a lower asthma prevalence than nonnatives (risk ratio [RR], 0.70; 95% confidence interval [CI], 0.66 – 0.75), but among the subgroup of children residing in the state’s major urban center, Alaska Natives had a higher prevalence. Overall, 0.22% of the study population experienced an asthma-related hospitalization, with Alaska Natives having a higher risk of hospitalization than nonnatives (RR, 1.6; 95% CI, 1.2–2.3). Among hospitalized children, Alaska Natives were less likely to have received a long-term control medication (RR, 0.54; 95% CI, 0.33– 0.88). Conclusions: Compared with nonnatives, Alaska Natives have a lower risk of asthma but only among nonurban residents. The increased risk of hospitalization among Alaska Natives may be related to underuse of long-term control medications. Ann Allergy Asthma Immunol. 2003;90:616– 621.
INTRODUCTION Asthma is one of the leading causes of childhood morbidity in the developed world and the most common chronic childhood disease in the United States.1,2 Furthermore, asthma prevalence appears to be increasing.3– 6 Although previous studies have evaluated asthma prevalence among minority populations,7–10 no evaluation has yet examined asthma among Alaska Natives. The current study was undertaken to evaluate asthma prevalence and asthma-related hospitalizations among Alaska Natives and nonnatives younger than 20 years who were enrolled in Medicaid during 1998 to 1999. Secondary evaluations examined the demographic risk factors for asthma and prevalence of long-term control medication use. METHODS Health Care in Alaska During the study period, health care services in Alaska were delivered through a variety of private, public, nonprofit, Native Corporation, and Indian Health Service entities. Alaska Natives constituted the state’s largest racial minority and predominant rural residents and usually received services through Native Corporation and Indian Health Service facilities. For Medicaid-enrolled persons, all in-state facilities
Alaska Division of Public Health, Anchorage, Alaska. Received for publication November 9, 2002. Accepted for publication in revised form March 8, 2002.
616
billed Medicaid regardless of where a specific individual obtained care. During the last 4 months of the study period, Alaska had in place Denali KidCare, the state’s Child Health Insurance Program that extended Medicaid coverage to all children younger than 19 years, including Indian Health Service and Native Corporation beneficiaries, at 200% of the federal poverty level. Data Source Multiple data files were obtained from the Alaska Division of Medical Assistance. The master file consisted of all persons younger than 20 years enrolled in Medicaid from July 1, 1998, through June 30, 1999. We could not use earlier data because until 1998 the Indian Health Service submitted Medicaid billing in batches, thus preventing analysis of outcomes by individual. The master file contained a unique identifier for each person and the person’s town or village of residence, race, sex, and date of birth. Not all children were enrolled in Medicaid for the entire study period, either because they lost their eligibility or enrolled after the beginning of the study. Among all children, 38% were continuously enrolled during the entire study period compared with 56% of children with asthma. Among children not continuously enrolled, the average length of enrollment was 5.7 months for all children and 7.6 months for children with asthma. Four files were obtained that contained all provider, inpatient facility, and outpatient hospital claims for International Classification of Diseases, Ninth Revision (ICD-9) codes 493.0x to 493.9x, the standard codes for asthma. A fifth
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subsidiary file was obtained for pharmacy claims paid by Medicaid. This file was limited to approved claims for the following medications manufactured by any company: oral or intravenous theophylline, inhaled or liquid albuterol, and inhaled bitolterol, pirbuterol, salmeterol, beclomethasone, triamcinolone, flunisolide, fluticasone, budesonide, cromolyn, nedocromil, zileuton, zafirlukast, montelukast, and ipratropium bromide. Cromolyn, nedocromil, salmeterol, leukotriene modifiers, methylxanthines, and inhaled steroids were classified as long-term control medications, whereas shortacting inhaled and oral -agonists and ipratropium bromide were classified as quick-relief medications. The pharmacy file had information on filled prescriptions, which reflects a combination of provider prescribing practices and patient prescription filling practices. These five files contained one record for each billing episode. Consequently, individuals might have had more than one record in any one file. Furthermore, these files did not describe mutually exclusive visits, since billing at some facilities included physician fees, whereas at other facilities physicians billed separately. Records for claims that were submitted but denied by Medicaid, usually because an individual was not enrolled at the time the service was provided, were not included in analysis. Case Definitions Asthma was defined as an approved claim for asthma-related medication use or care. Within this group, subgroups were also evaluated, including persons with approved claims for both medication and care and persons with approved claims for asthma-related inpatient care. Persons with asthma who did not receive an ICD-9 code for asthma or an asthmarelated medication during the study year were excluded from this case definition. Analysis The 1 pharmacy and 4 services-related data files were linked to the eligibility file by matching on the unique identifier number. Because asthma prevalence was the primary outcome of interest, all analyses were performed with the individual as the unit of analysis. Consequently, multiple visits or medications for a single person during the study year were ignored. Four major risk factors were available for analysis in the Medicaid database: sex, Alaska Native status, age, and census area of residence. Residence was categorized as Anchorage or non-Anchorage; Anchorage was the only substantial urban center and contained approximately half of the state’s population and 3 of its 4 largest hospitals. Recent data indicate that a substantial proportion of children may benefit from long-term control medication and particularly inhaled steroid use.11 Consequently, a separate analysis was conducted examining medication use. Because not all children with asthma necessarily had a medical indication for long-term control medications, this analysis concentrated on children with an asthma-related hospitalization.
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During univariate analysis, risk ratios and 95% confidence intervals (CIs) were calculated. Multiple logistic regression models were created to evaluate the independent association between outcome variables and Alaska Native status, age, sex, and census area of residence. For all models, all independent variables were entered simultaneously. All analyses were performed with SPSS version 10 statistical software (SPSS Inc, Chicago, IL). RESULTS Univariate Claims Prevalence and Identification of Risk Groups During the 1-year study period, 59,501 in-state residents younger than 20 years were enrolled in Medicaid and 4131 had one or more claims for asthma-related care or medication. The overall asthma prevalence was 6.9%; 6.1% of children received asthma-related medication, 3.2% received asthma-related care, 2.3% received both medication and care, and 0.22% had an asthma-related hospitalization. Among all children with asthma, 3.1% had one or more hospitalizations. The number of children with a first claim for asthma during the study period increased from 839 during the first 4 months of the study to 1,149 and 2,092 during the second and third 4 months of the study, respectively (for some children, the exact date of the first claim was not known). The proportion of children who experienced one of the measured outcomes was higher in males than females, children younger than 5 years than older persons, and persons living in the Anchorage census area than those living in less populated areas (Table 1). Compared with nonnatives, the overall asthma prevalence was lower among Alaska Natives, but the proportion who were hospitalized was higher. Among different census areas (Alaska does not have counties), overall asthma prevalence varied from 0 to 9.8%. The south central and southeast regions of Alaska, where most of the state’s population resided during the study period, had the highest prevalences. In the three most populous census areas, Alaska Natives had asthma prevalences of 11, 8.6, and 10% (in descending order of population) compared with 9.4, 7.2, and 7.9% for nonnatives. In less populous census areas, there was more variation between Alaska Native and nonnative asthma prevalences; much of this variation, however, might be attributed to the small number of cases at this level of stratification. Multivariate Risk Factor Analysis Sex, Alaska Native status, age, and Anchorage residence were all entered simultaneously into a multiple logistic regression model for each of the outcomes of interest. Similar to univariate analyses, male sex, nonnative status, age younger than 5 years, and living in the Anchorage census area were associated with overall asthma prevalence (Table 2). Male sex, Alaska Native status, and age younger than 5 years were risk factors for hospital care. In Alaska, Alaska Natives live predominantly in rural areas and nonnatives live predominantly in urban areas; Anchorage
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Table 1. Medicaid-Enrolled Alaska In-State Residents Younger than 20 Years who Experienced Various Asthma Outcomes, July 1998 through June 1999
Risk group
Race Alaska Native (n ⫽ 23,318) Nonnative (n ⫽ 36,183) Sex Male (n ⫽ 29,991) Female (n ⫽ 29,510) Age group, y 0–4 (n ⫽ 19,977) 5–9 (n ⫽ 16,811) 10–14 (n ⫽ 13,176) 15–19 (n ⫽ 9537) Census area of residence Anchorage (n ⫽ 19,250) Non-Anchorage (n ⫽ 40,251)
Asthma-related medication or care
Asthma-related medication and care
Asthma-related hospitalization
Residents, %
RR (95% CI)
Residents, %
RR (95% CI)
Residents, %
RR (95% CI)
5.5 7.9
0.70 (0.66–0.75) Referent
1.4 2.9
0.46 (0.41–0.53) Referent
0.28 0.17
1.6 (1.2–2.3) Referent
7.5 6.3
1.2 (1.1–1.3) Referent
2.6 2.0
1.3 (1.2–1.5) Referent
0.26 0.18
1.5 (1.0–2.1) Referent
10 5.1 5.2 5.4
1.9 (1.7–2.1) 0.95 (0.85–1.1) 0.97 (0.87–1.1) Referent
3.2 2.0 2.1 1.6
2.0 (1.7–2.4) 1.3 (1.0–1.5) 1.4 (1.1–1.6) Referent
0.40 0.12 0.10 0.17
2.4 (1.4–4.1) 0.71 (0.37–1.4) 0.59 (0.28–1.2) Referent
10 5.5
1.8 (1.7–1.9) Referent
3.2 1.9
1.7 (1.5–1.9) Referent
0.21 0.22
0.94 (0.65–1.4) Referent
Abbreviations: CI, confidence interval; RR, risk ratio.
is the largest city and center for medical care in the state. To more clearly illustrate the risk of asthma associated with Alaska Native status independent of residence, data were stratified into Anchorage and non-Anchorage residence. Then multiple logistic regression analyses were performed with Alaska Native status, male sex, and age younger than 5 years entered simultaneously. Compared with nonnatives, Alaska Native status was associated with an increased odds of asthma among Anchorage residents (odds ratio [OR], 1.2; 95% CI, 1.1–1.3) but a decreased odds of asthma among non-Anchorage residents (OR, 0.65; 95% CI, 0.59 – 0.71). A similar analysis was performed for hospitalizations. Alaska Native status was associated with an increased odds of asthma-related hospitalization among both Anchorage (OR, 2.5; 95% CI, 1.3– 4.7) and non-Anchorage (OR, 1.5; 95% CI, 0.95–2.2) residents. Differences between populations in the proportion of children hospitalized for asthma may reflect differences in the proportion of children with asthma who become hospitalized or differences in the underlying asthma prevalence. To distinguish between these possibilities, the final set of multivariate analyses determined the proportion of children who had
1 or more hospitalizations among the subgroup of children with asthma. Among the subgroup of children with asthma (and similar to results for the entire population of Medicaideligible children), Alaska Native status was associated with an increased odds of asthma-related hospitalization among both Anchorage (OR, 2.2; 95% CI, 1.2– 4.2) and non-Anchorage residents (OR, 2.0; 95% CI, 1.3–3.1). Medication Use Among the 4,131 children with asthma, 86% received at least one quick-relief medication, 18% received at least one longterm control medication, and 10% received at least one inhaled steroid. Among the subgroup of 1,262 children who received both medication and care, 36% received a long-term control medication and 21% received an inhaled steroid. Among the subgroup of 129 hospitalized children, 36% received a long-term control medication and 23% received an inhaled steroid. Among hospitalized children, Alaska Natives, children younger than 5 years, and non-Anchorage residents were less likely than nonnatives, older children, and Anchorage residents to have received long-term control medications or inhaled steroids (Table 3).
Table 2. Multiple Logistic Regression Analysis for Various Asthma Outcomes among Medicaid-Enrolled Alaska In-State Residents Younger than 20 Years, July 1998 through June 1999 OR (95% CI) Risk group
Alaska Native Male Age ⬍5 y Anchorage resident
Asthma-related medication or care
Asthma-related medication and care
Asthma-related hospitalization
0.81 (0.75–0.87) 1.2 (1.1–1.3) 2.0 (1.9–2.2) 1.8 (1.7–1.9)
0.51 (0.45–0.58) 1.3 (1.2–1.5) 1.6 (1.5–1.8) 1.5 (1.3–1.6)
1.7 (1.2–2.4) 1.4 (1.0–2.0) 3.3 (2.3–4.7) 1.1 (0.71–1.5)
Abbreviations: CI, confidence interval; OR, odds ratio.
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Table 3. Medicaid-Enrolled Alaska In-State Residents Younger than 20 Years who Had Been Hospitalized for Asthma and who Received Any Long-term Control Medication or Inhaled Steroids Alone, July 1998 through June 1999 Long-term medication*
Inhaled steroid
Risk group Race Alaska Native Nonnative Sex Male Female Age group, y 0–4 5–9 10–14 15–19 Census area of residence Anchorage Non-Anchorage
Residents, %
RR (95% CI)
Residents, %
RR (95% CI)
26 48
0.54 (0.33–0.88) Referent
17 29
0.58 (0.30–1.1) Referent
34 40
0.84 (0.53–1.3) Referent
17 31
0.55 (0.29–1.0) Referent
26 55 62 44
0.60 (0.31–1.2) 1.3 (0.64–2.5) 1.4 (0.70–2.8) Referent
11 40 46 38
0.30 (0.12–0.73) 1.1 (0.47–2.4) 1.2 (0.52–2.9) Referent
44 33
1.4 (0.86–2.1) Referent
35 16
2.1 (1.1–4.0) Referent
Abbreviations: CI, confidence interval; RR, risk ratio. * Long-term medications included inhaled steroids, methylxanthines, cromolyn, nedocromil, salmeterol, and leukotriene modifiers.
Inhaled steroid use was examined in more detail. Of the 426 children who filled a prescription for inhaled steroids, 254 (60%) filled a single prescription (range of filled prescriptions, 1–13; median, 2). To determine if children appropriately refilled inhaled steroid prescriptions, the interval between refills was examined for the 172 children who filled at least two prescriptions. For all children, the median length of time between refills was 45 days, with 28% of refills occurring within 30 days and 62% occurring within 60 days. No difference existed between Alaska Natives and nonnatives in the median length of time between prescription refills. DISCUSSION Among the Alaska Medicaid-enrolled population younger than 20 years, asthma prevalence was 6.9% and 0.22% were hospitalized with asthma. Comparisons with other studies are problematic because of differing methods, particularly the case definition of asthma. Several similar studies12–14 of Medicaid populations suggest that overall asthma prevalence in other states is 1.5 to 2 times higher than in Alaska. The occurrence of hospitalization for asthma in Alaska is lower than in Michigan,3 comparable to Connecticut,14 and higher than in Nebraska.13 This is the first study, to our knowledge, to examine Alaska Native asthma prevalence. Overall, Alaska Natives had a lower asthma prevalence than nonnatives; stratified analysis, however, showed that this difference existed only for residents living outside Alaska’s major urban center. Among nonurban residents, Alaska Natives tend to live in smaller communities and to have lived for a longer period in those communities than nonnatives. Consequently, nonurban Natives may have received less exposure than nonnatives to whatever factors have led to the documented increase in asthma prevalence in more urban communities.4,7,8,15,16 In
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rural Alaska, an extensive system of Native Corporation and Indian Health Service health care facilities provides free care to Alaska Natives, whereas no similar health insurance system exists for nonnatives; thus, it is unlikely that poor access to care and underreporting explain the low asthma prevalence among nonurban Alaska Natives. The relatively high risk of asthma among urban Alaska Natives suggests that previously reported genetic differences17,18 also do not explain the observed racial differences in asthma prevalence. Independent of residence in Alaska’s urban center, Alaska Natives with asthma were more likely to have an asthmarelated hospitalization than nonnatives. Some other studies3,16,19 have also found that minority populations are more likely to be hospitalized for asthma, whereas at least one study20 found that American Indians and Alaska Natives grouped together do not have an increased risk of hospitalization. Several potential reasons exist for the findings from the current study. Because provision of care in Alaska is largely stratified by Alaska Native status, differences in therapeutic strategies between care providers might contribute to different hospitalization rates. The only therapy-related outcome available for measurement, long-term control medication use, provided some support for this hypothesis, since hospitalized Alaska Natives were significantly less likely than nonnatives to have received a long-term control medication, including inhaled steroids. Alaska Native children have some of the highest respiratory syncytial virus and pneumococcal pneumonia incidences ever reported.21,22 Although early exposure to environmental toxins may decrease the risk of developing asthma,18 respiratory infections may increase the risk of hospitalizations among children who have asthma.23 Alternatively, the results may reflect a variety of biases, including differences among providers with respect to
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assigning a diagnosis of asthma and differences in provider or self-referral patterns for hospitalization. Long-term control medications, particularly inhaled corticosteroids, have become the accepted standard for ongoing management of persistent asthma.11 Use of these medications in the current study population, however, was low, particularly among high-risk children. Although some subpopulations were particularly unlikely to have received long-term control medications, such as Alaska Natives and younger children, long-term control medication use was low among all groups evaluated, a finding documented in other populations as well.24 This result may reflect either failure of providers to prescribe long-term control medications or failure of patients to fill prescriptions. Among children who used inhaled steroids, 40% had an elapsed time between prescription refills of more than 60 days, the maximum length of time a standard 120-dose inhaler would last assuming continuous twice-daily use. These results suggest the need for intervention programs to increase the use of steroid and other longterm control medications, including education programs, improving patient-physician interactions, implementation of National Asthma Education and Prevention Program guidelines for the diagnosis and management of asthma (www. nhlbi.nih.gov/about/naepp/), and possibly provider home visitations for children with more severe asthma. The current study has several limitations. It relies on Medicaid claims data rather than parent or patient surveys as has been performed for the most recent studies of asthma prevalence.25 It also relies on ICD-9 coding, which is unlikely to identify all cases of asthma. For both of these reasons, asthma prevalence, particularly for mild cases, may have been underestimated. Alternatively, we may have overestimated asthma prevalence by including oral -agonist medications, particularly among younger children who may receive these medications for upper respiratory tract illnesses. The data set was restricted to children enrolled in Medicaid during the study year, and these children may have different asthma prevalences than the remaining population of Alaska children.26 Finally, the short study period precluded evaluation of temporal trends. Compared with nonnatives, rural Alaska Native children had a low asthma prevalence, whereas urban Alaska Natives had a high prevalence. Further evaluation of the reasons for this finding may shed light on the mechanisms associated with the recent increase in asthma prevalence throughout the United States. Alaska Natives had a relatively high risk of asthma-related hospitalization, possibly due to underuse of long-term control medications. Although long-term control medication use was low among all populations, intervention programs to improve medication use and adherence27 targeted toward Alaska Natives and their care providers may help decrease the excess hospitalization seen among this population. The ongoing use of the Medicaid database for surveillance could help determine if Alaska is meeting Healthy People 2010 goals for reductions in asthma morbidity, particularly asthma-related hospitalizations.
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20. Hisnanick JJ, Coddington DA, Gergen PJ. Trends in asthmarelated admissions among American Indian and Alaskan native children from 1979 to 1989: universal health care in the face of poverty. Arch Pediatr Adolesc Med. 1994;148:357–363. 21. Karron RA, Singleton RJ, Bulkow L, Parkinson A, Kruse D, et al. Severe respiratory syncytial virus disease in Alaska native children. RSV Alaska Study Group. J Infect Dis. 1999;180: 41– 49. 22. Davidson M, Parkinson AJ, Bulkow LR, Fitzgerald MA, Peters HV, Parks DJ. The epidemiology of invasive pneumococcal disease in Alaska, 1986 –1990: ethnic differences and opportunities for prevention. J Infect Dis. 1994;170:368 –376. 23. Glezen WP, Greenberg SB, Atmar RL, Piedra PA, Couch RB. Impact of respiratory virus infections on persons with chronic underlying conditions. J Am Med Assoc. 2000;283:499 –505. 24. Donahue JG, Fuhlbrigge AL, Finkelstein JA, Fagan JA, Livingston JM, et al. The Pediatric Asthma Care Patient Outcomes Research Team. Asthma pharmacotherapy and utilization by children in 3 managed care organizations. J Allergy Clin Immunol. 2000;6:1108 –1114.
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25. Asher MI, Keil U, Anderson HR, Beasley R, Crane J, et al. International Study of Asthma and Allergies in Childhood (ISAAC): rationale and methods. Eur Respir J. 1995;8: 483– 491. 26. Finkelstein JA, Barton MB, Donahue JG, Algatt-Bergstrom P, Markson LE, Platt R. Comparing asthma care for Medicaid and non-Medicaid children in a health maintenance organization. Arch Pediatr Adolesc Med. 2000;154:563–568. 27. Fish L, Lung CL, The Antileukotriene Working Group. Adherence to asthma therapy. Ann Allergy Asthma Immunol. 2001; 86:24 –30. Requests for reprints should be addressed to: Bradford D. Gessner, MD, MPH Alaska Division of Public Health 3601 C St PO Box 240249 Anchorage, AL 99524 E-mail: [email protected]
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