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Prevalence and treatment of asthma in the Michigan Medicaid patient population younger than 45 years, 1980–1986
Original
articles
Prevalence and treatment of asthma in the Michigan Medicaid patient population younger than 45 years, 1980-1986 B. Burt Gerstman, DVM, MPH, PhD, Lynn A. Bosco, MD, MPH, Dianne K. Tomita, MPH, Thomas P. Gross, MD, MPH, and Michelle M. Shaw, PharmD Rockville, Md., and Arlington, Va. The prevalence and outpatient treatment of asthma were studied in the Michigan Medicaid patient population by use of computerized physician, hospital, and pharmacy reimbursement data to mark and track asthma-related medical transactions. Asthma cases were defined as patients with evidence of at least two diagnoses and prescription drug transactions consistent with asthma. More than 52,000 cases were thus ident$ed. The period prevalence of asthma was estimated on a year-by-year basis. The prevalence of asthma in the population increased from 2 .O per ,!OO Medicaid patients in 1980 to 2.8 per 100 Medicaid patients in 1986. Prevalence decreased with age until the age of 20 years and increased thereafter, and was higher in male children than in female children. In contrast, asthma was more prevalent in female adults than in male adults. Prevalence was higher in black subjects than in other races and higher in urban residents than in rural residents. The total number of reimbursements for antiasthma medications increased from 60,000 per year to 120,000 per year, and the average number of antiasthma prescriptions per Michigan Medicaid asthma case increased at the rate of 6.6% per year during the study interval. Changes in the preferred types of asthma treatment consistent with changes that have occurred in the general population were observed. These data suggest that the (relative and absolute occurrence of asthma and asthma treatment in the Michigan Medicaid population is increasing. (J ALLERGY CLINIMMUNOL 1989;83:1032-9.)
Asthma is a leading cause of morbidity affecting >8.5 million people in the United States.‘. ’ It is one of the most common chronic diseases of childhood and is a leading cause of disability in subjects younger than the age of 17 years. 24 Despite introduction of new drugs and new drug formulations for the treatment of asthma, asthma morbidity and mortality have not declined either in the United States or abroad.7-‘2 This fact has raised concern about current asthmamanagement practices. 1246
From the Food and Drng Administration, Office of Epidemiology and Biostatistics, Rockville, Md., and Health Information Designs, Inc., Arlington, Va. The views expressed in this manuscript are those of the authors and do not necessarily reflect the opinion or policy of the Food and Drug Administration. Received for publication May 19, 1988. Revised Oct. 24, 1988. Accepted for publication Nov. 8, 1988. Reprint requests: B. Gerstman, DVM, MPH, PhD, Office of Epidemiology and Biostatistics, Food and Drug Administration, 5600 Fishers Lane, Room 15-42, Rockville, MD 20857. 1032
I Abbreviations COMPASS:
NPA: MDI: I
used Computerized On-line Medicaid Pharmaceutical Analysis and Surveillance System National prescription audit Metered-dose inhaler
I
I
Information about treatment of asthma on a population basis is generally lacking. Previous studies have used data obtained from selected outpatient pharmacies to determine trends and patterns of asthma treatment in the population. ‘3“3 ‘K I7 These previous studies suggest that the number of dispensed prescriptions for antiasthma drugs has increased markedly since the late 1970s and that significant changes in the relative frequency in type of drug treatment and route of administration have occurred. I53I7 In these studies, however, it has not been possible to distinguish between use of bronchodilator drugs for the treatment of asthma and other respiratory conditions. It has also been impos-
Asthma
VOLUME 83 NUMBER 6
I. Average
TABLE
yearly
prevalence
by age, sex, race, and resi’dence, Prevalence by sex
Overall Age (yr) 0 to 5 to 15 to 20 to 30to oto
in Michigan
Medicaid
1033
1980-1986
Prevalence
Prevalence residence
by race
by
Cases
COMPASS
4 14 19
6,360 6,01;!
29
2,59ll 3,550 19,977
186,932 199,821 95,668 168,635
1,463
44 44
Prevalences
116,724 767,780
are per 100 Michigan
Medicaid
Prevalence 3.4 3.0 1.5 1.5 3.0 2.6
M
F
Black
White
Other
Urban
Rural
4.2 3.7 1.7
2.5 2.3 1.4
4.9 4.6 2.2
3.0 2.4 1.3
1.7
2.3
1.4
1.6 3.1
3.5 2.3
4.3 3.8
2.8 2.3
3.8 3.4 1.7 1.8 3.5 2.9
2.1 1.7
1.0
1.9 1.7 .9 .8 1.6 1.5
METHODS Data base Data presentedin this article are derived from COMPASS (Health Information Designs, Inc., Arlington, Va.). Briefly, COMPASS is a large computerized data base of Medicaid billing data that has been developed for the postmarketing surveillanceof drugs. COMPASSdata originate from a computerized claims-processingsystem designed for fiscal and administrative control of Medicaid programs. Data are organized into patient records known as “profiles” in which Medicaid-reimbursed health care transactionsare arranged according to the date service was provided. This permits construction of medical service histories over time and enables these data to be used for postmarketing drng surveillance.‘*. I9
and operative
.7 1.7 1.5
recipients.
sible to determine the number and type of subjects treated. The present study reports trends and patterns in asthma diagnosis and treatment in the Michigan Medicaid patient population for the interval 1980 through 1986. Prevalence and frequency of drug use are determined with two different drug classification schemes. Changes in patterns of drug use, number of patients with asthma, and number of antiasthma prescriptions per patient are described.
Study population of asthma
1.0
definition
The study population was defined on a yearly basis and included Michigan Medicaid enrollees younger than 45 years that demonstrated at least one reimbursement for services in their COMPASS profile. The primary manner in which individuals in this age range become eligible for Medicaid benefits is:through the Aid to Families with Dependent Children programs. It is therefore not surprising to find that the study population primarily consistedof children and women of childbearing age (Table I). Our method of case ascertainment relied on physician and hospital billing codes suggestive of asthma diagnoses and treatments. To increasethe accuracyof distinguishing
potential casesfrom noncases, we focused on those individuals who had at least two diagnoses of asthma (International Classification of Disease, 9th revision, Clinical Modification code 493) and at least two pharmacy claims for drugs primarily used to treat asthma within their COMPASS history. With this case definition, a total of 52,231 Medicaid subjects with asthma were identified.
Monitoring
disease and drug use
To estimate the period prevalenceof asthma, profiles of the aforementioned individuals were scannedfor diagnostic and drug transactionssuggestiveof clinically active asthma. Yearly prevalencesfor the interval 1980 through 1986 were determined by age, sex, race, and residence.For the purpose of this article, Metropolitan StatisticalArea residents were considered to be “urban,” and non-Metropolitan Statistical Area residentswere consideredto be “mral.” Prevalencefor each year is reported per 100 Medicaid benefit recipients. Drug use prevalence was estimated as the proportion of subjects with active asthma reimbursed for drugs of predefined classes. The following drug classes were used: MDIs, nebulizer solutions, sodium cromolyn, sustained-releasetbeophyllines, immediate-releasetbeophyllines, fixed-combination products, oral sympathomimetic drugs, systemiccorticosteroids, and inhaled corticosteroids. Drug-use prevalencefor eachyear is reported per 100 asthma cases. In addition, drugs were classifiedaccording to their primary pharmaceuticalmode of action, ignoring route of administration and formulation type. The following mode of action classes were used: xanthines, which included sustained-releasetheophyllines, immediate-releasetheophyllines, and fixed-combination products with at least one theophylline constituent; adrenergic drugs, which included MDIs, nebulizer solutions, oral sympathomimetic drugs, and those fixed-combination products with adrenergiccomponents; and anti-inflammatory drugs, which included systemic corticosteroids, inhaled corticosteroids, and sodium cromolyn. Note that fixed-combination products are double counted as both xanthines and adrenergic drugs according to this scheme. The total and average number of Medicaid reimburse-
1034
Gerstman
et al.
01 O-4
J. ALLERGY CLIN. IMMUNOL. JUNE 1999
!
I
I
/
I
I
I
,
5-9
lo-14
15-19
20-24
25-29
30-34
35-39
40-44
Age
Males
Females -----______
FIG. 1. Average annual prevalence of asthma in subjects younger than 45 years in the Michigan Medicaid population by age and sex for the period 1980-1986.
TABLE II. Number of asthma cases, individuals in the COMPASS system, and prevalence from birth to 44 years, 1980-1986 Year
Cases
COMPASS
1980
14,698
751,231
1981 1982 1983 1984 1985 1986
17,747 20,024 22,641 23,333 21,35’7 20,036
809,467 780,140 833,317 783,308 707,916 709,087
Prevalence
2.0 2.2 2.6 2.7 3.0 3.0 2.8
ments for antiasthma drugs used by caseswas determined. Average rates of change per year were calculated by the following formula: (x,.hoY’” - 1 where %., denoteseither the prevalenceor number of events observed during the rP interval in question and xc,,)denotes the prevalenceor number of events during the first interval in question.” Although this formula may falsely assumea constant rate of change, it can, nonetheless, be useful in providing a summary statisticfor the purpose of describing trends. RESULTS Prevalence
of asthma
Average annual prevalences by age, sex, race, and residence status are listed in Table I. The prevalence
of asthma reaches its minimum at age 20 years. The prevalence of asthma was higher in male subjects younger than 20 years than in female subjects of comparable age, but was higher in female subjects older than 20 years than in male subjects of comparable age (Fig. 1). The overall prevalence was higher in black subjects than in white subjects and other races (3.8 versus 2.3 versus 1S, respectively), and was higher in urban dwellers than in rural dwellers (2.9 versus 1.5, respectively). Table II contains the number of cases, Michigan Medicaid benefit recipients in the COMPASS system, and prevalence of asthma from birth to 44 years for each of the 7 years of the study. During this interval, the prevalence increased from 2.0 to 2.8 per 100 Michigan Medicaid benefit recipients per year. This represents a 40% increase during 7 years of observation. Prevalence
of drug use
Table III contains drug use prevalence estimates by age. Overall, use of sustained-release theophylline increased at an average rate of 17% per year. A concomitant drop in the use of immediate-release theophylline occurred in all ages except from birth to 4 years in which use of this class of drug remained relatively constant. The prevalence of fixedcombination product use decreased dramatically over time, averaging a 22.3% decline per year. The use of
Asthma in Michigan
VOLUME 83 NUMBER 6
TABLE
III. Prevalence
of drug
use per 100 patients
0 to 4 Age group (VI
Drugs used Sustained-release theophylline Immediatereleasetheophylline Fixedcombination Oral sympathomimetic MDIs Nebulizer solutions Sodium cromolyn Inhaled corticosteroids Systemiccorticosteroids
with
5 to 9
1035
by age, 1980 and 1986 20 to 29
15 to 19
10to14
30 to 44
1980
1988
1980
1988
1980
1988
1980
1988
1980
1988
1980
I!388
7
48
23
55
31
60
25
59
24
59
25
63
37
39
27
20
26
10
32
8
39
10
39
11
56
5
51
7
43
8
35
10
35
10
39
16
17
49
20
38
22
29
25
19
27
24
30
27
0 1
2 9
3
19 8
9
1
56 3
19
1
47 6
16
1
1
56 4
21 3
52 6
0
6
3
8
5
7
3
3
2
3
3
3
0
0
3
4
6
7
5
7
7
8
9
11
4
8
7
10
11
13
16
19
22
25
24
30
oral sympathomimetic drugs remained constant in adults and adolescents, but demonstrated more than a doubling in patients younger than 10 years.
Overall, MD1 use increased at a rate of 22.3% per year. More than half the identified patients with asthma older than 15 years received at least one MD1 prescription in 1986. In addition, it was somewhat surprising to find that the prevalence of MD1 use in children 5 to 9 years increased from 3% in 1980 to 19% in 1986. Nebulizer solutions, inhaled corticosteroids, and sodium cromolyn were used by relatively few subjects with asthma. Systemic corticosteroid use was age related; 30-year-old patients were more than three times as likely to receive systemic steroids than subjects with asthma younger than 10 years. Overall, systemic steroid use among asthma patients increased modestly. Number
asthm.a
Medicaid
of prescriptions
Changes in the total and average number of antiasthma prescriptions per case are illustrated in Fig. 2. The total number of prescriptions doubled from just under 60,000 to nearly 120,000 per year (12.2% rate of increase per year). Simultaneously, the number of cases increased from 14,698 in 1980 to 20,036 in 1986 (Table II). Accordingly, the average number of prescriptions per patient increased from 4.07 in 1980 to 5.98 in 1986 (6.6% rate of increase per year). There was a threefold increase in sustained-release
theophylline use, a twofold increase in oral sympathomimetic prescription use, and a sixfold increase in MD1 use (Fig. 3). There was nearly a twofold decreased in fixed-combination product use and a slight decrease in immediate-release theophylline use. The number of reimbursements for nebulizer solutions, cromolyn sodium, systemic corticosteroids, and corticosteroid inhalers increased slightly. The number of Medicaid reimbursements and percent of market share by the aforementioned broad mode of action categories (see Methods section) are presented in Table IV. The number of reimbursements for xanthines peaked in 1984. There was a :steady increase in the number of adrenergic and anti-inflammatory drugs. Adrenergic and antiinflammatory drugs steadily increased market share. Comparison of Medicaid use estimates
and NPA drug
Previously reported NPA drug-use estimates (IMS America, Ltd., Ambler, Pa.) are used for comparison with Medicaid data. Since NPA data do not assess drug treatment in relation to disease, comparisons are restricted to oral bronchodilator, inhaled bronchodilator, and inhaled anti-inflammatory drug-use estimates. NPA projections suggest that the use of the drug classes in question, irrespective of indication, increased from 37 million prescriptions in 1981 to 5 1
1036
Gerstman
et al.
J. ALLERGY CLIN. IMMUNOL. JUNE 1989
/
5
4 07
4.25
11111 4 26
1980
1981
1382
4.79
5.06
5.2
1983
1954
1985
98
1986
Year PrescrIptions
per
Case
FIG. 2. Total and average number of among subjects with asthma 1980-1986.
Total
Medicaid
TABLE IV. Reimbursed prescriptions and percent year and primary pharmacologic mode of action,
Prescrmpt~ons
reimbursement
for
antiasthma
of market share within 1980 through 1986
a given
Xanthine
prescriptions
year (percent)
Adrenergic
by
Anti-inflam
Year
n
%
n
%
n
%
1980
39,950 48,264 50,726 61,075 63,221 54,461 55,468
48.8 49.1 47.7 46.9 45.8 43.8 42.0
34,153 40,370 44,343 55,129 59,753 55,155 60,298
41.7 41.1 41.7 42.3 43.3 44.3 45.7
7,808 9,580 11,235 14,158 15,124 14,852 16,250
9.5 9.8 10.6 10.9 11.0 11.9 12.3
1981 1982 1983 1984 1985 1986
Anri-infim, anti-inflammatory. Fixed combination products
are counted
as both xanthines
and adrenergic
million prescriptions in 1985.” This represents an 8.4 average annual rate of increase. During this same period, use of these drugs in the identified Medicaid population with asthma increased from 75 5 thousand prescriptions to 111.1 thousand prescriptions. This represents a 10.2% annual rate of increase. Moreover, parallel changes in market share of the considered drug classes are observed (Fig. 4). For example, sustained-release theophylline formulations accounted for 22% of the total number of prescriptions of the considered drug classes in 1981 by both NPA and Medicaid estimates. By 1985, sustained-release
drugs.
theophyllines increased to 38% and 36% of use in NPA and Medicaid estimates, respectively. Other drug classesshifted market share in consort, suggesting that trends in bronchodilator therapy in Medicaid subjects with asthma parallel that of the general population, indication of use notwithstanding. DISCUSSION Prevalence of asthma Comparisons of the asthma-prevalence estimates among various studies are difficult because of dissimilarities in case definitions and case-ascertainment
Asthma
VOLUME 83 NUMBER 6
in Michigan
Medicaid
1037
-s+SRTheo
0‘I
980
1981
1982
1983
1984
1985
-
MDI
-
POSym
-+
IRTheo
-
FComb
+
sysst
+ -.+-4
NebSol Crom InSt
1986
Year FIG. 3. Number of reimbursements for sustained-release theophylline inhalers (MD/), oral sympathomimetic drugs (POSym), immediate-release systemic steroids (SysSt), nebulizer solutions (NebSol), cromolyn products {FComb), and inhaler corticosteroids (/nSt), 1980-1986.
Percent Market Share, 1981
W?Theo), metered-dose theophylline f/RTheo), (Cram), fixed-combination
Percent Market Share, 1985
.36
36
30
30
26
26
20
20
16
16
10
10
6
6
0
SRTheo IRTheo
FComb
POwm
D&g m
Vational
(NPA)
MDI
NabSol
Cram
blst
0
SRTheo
IRTheo
FComb
@
POwm
MDI
NebSol
Croln
Drug Class
Class Medicafd
m
National
FIG. 4. Comparison of national and Medicaid drug estimates. A comparison bution of outpatient prescriptions for a selected group of antiasthma drugs, versus Michigan Medicaid asthma cases, 1981 and 1985.
methods.21.22For example, nationwide (United States) estimates of asthma prevalence, as determined by the National Center for Health Statistics, are often derived by survey questionnaire. In contrast, our method of case ascertainment relied on billing codes from health care providers for asthma-related medical transactions. In our opinion, our method is likely to be less sensitive, but more specific, than questionnaire-
INPA)
@
MedlCaid
of percent distriNPA projections
derived estimates. Therefore, it was not surprising to find that our prevalence estimates were lower than estimates of the National Center for Health Statistics for the United States as a whole.‘.“* 5 However, in spite of differences in methods and possible nonrepresentativeness of the population under study, several important patterns of disease are readily apparent. For example, decreasing prevalence
1038
Gerstman
et al.
with age during late adolescence and early adulthood followed by increasing prevalence with age during the latter half of the third decade onward has been reported.‘, 3-5, 23 The higher prevalence in male children and adolescents compared to female children and adolescents has also been widely reported.” 23-28In addition, the higher prevalence in black subjects compared to white subjects is consistent with previously published studies. *, *’ We found a higher prevalence of asthma in urban residents than in rural residents, suggesting a disparity in either disease occurrence or health care practices. Note that no adjustment has been made for race in these analyses; therefore, the apparent urban excess may partially reflec:t the unequal distribution of race in the Medicaid population, with few black subjects in the rural Medicaid population. Increases in asthma prevalence over time may reflect actual increases in prevalence or trends in diagnostic and treatment practices. In either event, increases in the number of Medicaid patients with asthma must be considered when drug use is interpreted for estimates. Drug use
Sustained-release theophylline and oral sympathomimetic drugs have replaced fixed-combination products as the preferred treatment for asthma in children. Sustained-release theophylline and MDIs have replaced immediate-release theophylline and fixedcombination products as the preferred treatment for asthma in adolescents and adults. In addition, a significant proportion of adults with asthma use systemic steroids during their course of therapy. Increasing use of oral sympathomimetic drugs in young children and use of MDIs in adolescents and adults has resulted in a general trend toward greater reliance on sympathomimetic drugs for asthma treatment (Table IV). The average number of antiasthma drug reimbursement per Michigan Medicaid asthma case increased at the rate of 6.6% lper year during the study interval. This is more than three times the rate of overall Medicaid drug reimburs’ement nationwide. (The U.S. Department of Health and Human Services reported a 2% annual growth of Medicaid drug reimbursements nationwide for the period 1973 through 1983.29) It therefore appears that the rise in antiasthma drug use is not simply an artifact of the reimbursement system. In summary, the relative and absolute occurrence of asthma and asthma treatment in the Michigan Medicaid population appears to be increasing. We expressour graritude for the programming assistance of Ms. Dede Hill, and the epidemiologic advice of Dr. Frank Lundin, Dr. Carlene :Baum, and Dr. Joel Ku&sky.
J. ALLERGY CLIN. IMMUNOL. JUNE 1989
REFERENCES 1. Evans R, Mullally DI, Wilson RW, et al. National trends in the morbidity and mortality of asthma in the U.S.: prevalence, hospitalization, and death from asthma over two decades: 1965 1984. Chest 1987;91(suppl):65S-74s. 2. Stribolt TB. Asthma. In: Bone RC, ed. Medical clinics of North America. Philadelphia: WB Saunders, 1986:909-20. 3. National Center for Health Statistics. Current estimates from the National Health Interview Survey, United States, 1982. DHHS Publication No. (PHS) 85-1578 1985:82-96. 4. Current estimates from the National Health Interview Survey, United States, 1983. Hyattsville, Md.: National Center for Health Statistics, DHHS Publication No. (PHS) 86-1582. 1986:81-96. 5. Gergen PJ, Mullally DI, Evans R. National survey of prevalence of’ asthma among children in the United States, 1976 to 1980. Pediatrics 1988;81:1-7. Fleming DM, Crombie DL. Prevalence of asthma and hay fever in England and Wales. Br Med J 1987;294:279-83. Bumey PG. Asthma mortality in England and Wales: evidence for a further increase, 1974-84. Lancet 1986;2(8502):323-6. Sinclair BL, Clark DW, Sears MR. Use of anti-asthma drugs in New Zealand. Thorax 1987;42(9):670-5. Barger LW, Vollmer WM, Felt RW, Buist AS. Further investigation into the recent increase in asthma death rates: a review of 41 asthma deaths in Oregon in 1982. Ann Allergy 1988;60(1):31-9. 10. Mao Y, Semenciw R, Morrison H, et al. Increased rates of illness and death from asthma in Canada. Can Med Assoc J 1987;137(7):620-4. 11. Jackson RT, Beaglehole R, Rea HH, et al. Mortality from asthma: a new epidemic in New Zealand. Br Med J 1982; 285:771-4. 12. Hay IF, Higenbottam TW. Has the management of asthma improved? Lancet 1987;2(8559):609-11. 13. Barbee RA. The epidemiology of asthma. Monogr allergy 1987;21:21-41. 14. Holland WW. Introduction. Chest 1987;91(suppl):65S. 15. Keating G, Mitchell EA, Jackson R, et al. Trends in sales of drugs for asthma in New Zealand, Australia, and the United Kingdom, 1975-81. Br Med J 1984;289:348-51. 16. Lanes SF, Walker AM. Do pressurized bronchodilator aerosols cause death among asthmatics? Am J Epidemiol 1987;125:75566. 17. Bosco LA, Knapp DE, Gerstman B, et al. Asthma drug therapy trends in the United States, 1972 to 1985 [Workshop]. J ALLERGY CLIN IMMUNOL 1987;80:398-402. 18. Ixssler JT, Harris BSH. Medicaid data as a source for postmarketing surveillance information. Unpublished federal document. U.S. Government Contract 223-82-3021. February 1984. 19. Strom BL, Carson JL, Morse ML, et al. The computerized on-line medicaid pharmaceutical analysis and surveillance system: a new resource for postmarketing drug surveillance. Clin Pharmacol Ther 1985;38:359-64. 20. Computer Associates. SuperCalc4 User’s Guide and Reference Manual. 2nd ed. 1986. 21. Usherwood TP. Factors affecting estimates of prevalence of asthma and wheezing in childhood. Fam Pratt 1987;4:318-321. 22. Bumey P, Detels R, Higgins M, et al. Recommendations for research in the epidemiology of asthma. Chest 1987;91 (suppl): 194S-6s. HR, Bland JM, Pate1 S, et al. The natural history 23. Anderson of asthma in childhood. J Epidemiol Community Health 1986;40(2):121-9.
Asthma in Michigan
VOLUME 83 NUMBER 6
24. Pedersen PA, Weeke ER. Epidemiology of asthma in Denmark. Chest 1987;91(suppl 6):107S-14s. 25. Smith JM. The pmvalence of asthma and wheezing in children. Br J Dis Chest 1976;70:73-7. 26. Peckham C, Butler N. A national study of asthma in childhood. J Epidemiol Community Health 1978;32:79-85. 27. Mak H, Johnston P, Abbey H, et al. Prevalence of asthma and health service utilization of asthmatic children in an inner city. J ALLERGY CLIN IMMUNOL 1982;70(5):367-72.
Medicaid
1039
28. Tuchinda M, Habananada S, Vereenil J, et al. Asthma in Thai children: a study of 2000 cases. AM Allergy 1987;59(3):20711. 29. Ruther M, Pagan-Berlucchi A, Wivell K, et al. Health Care Financing Program Statistics. Medicare and Medicaid data book, 1986, 4CFA Pub. No. 03247. Washington, D.C.: U.S. Government Printing Office, 1987:15-34.
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articles
Prevalence and treatment of asthma in the Michigan Medicaid patient population younger than 45 years, 1980-1986 B. Burt Gerstman, DVM, MPH, PhD, Lynn A. Bosco, MD, MPH, Dianne K. Tomita, MPH, Thomas P. Gross, MD, MPH, and Michelle M. Shaw, PharmD Rockville, Md., and Arlington, Va. The prevalence and outpatient treatment of asthma were studied in the Michigan Medicaid patient population by use of computerized physician, hospital, and pharmacy reimbursement data to mark and track asthma-related medical transactions. Asthma cases were defined as patients with evidence of at least two diagnoses and prescription drug transactions consistent with asthma. More than 52,000 cases were thus ident$ed. The period prevalence of asthma was estimated on a year-by-year basis. The prevalence of asthma in the population increased from 2 .O per ,!OO Medicaid patients in 1980 to 2.8 per 100 Medicaid patients in 1986. Prevalence decreased with age until the age of 20 years and increased thereafter, and was higher in male children than in female children. In contrast, asthma was more prevalent in female adults than in male adults. Prevalence was higher in black subjects than in other races and higher in urban residents than in rural residents. The total number of reimbursements for antiasthma medications increased from 60,000 per year to 120,000 per year, and the average number of antiasthma prescriptions per Michigan Medicaid asthma case increased at the rate of 6.6% per year during the study interval. Changes in the preferred types of asthma treatment consistent with changes that have occurred in the general population were observed. These data suggest that the (relative and absolute occurrence of asthma and asthma treatment in the Michigan Medicaid population is increasing. (J ALLERGY CLINIMMUNOL 1989;83:1032-9.)
Asthma is a leading cause of morbidity affecting >8.5 million people in the United States.‘. ’ It is one of the most common chronic diseases of childhood and is a leading cause of disability in subjects younger than the age of 17 years. 24 Despite introduction of new drugs and new drug formulations for the treatment of asthma, asthma morbidity and mortality have not declined either in the United States or abroad.7-‘2 This fact has raised concern about current asthmamanagement practices. 1246
From the Food and Drng Administration, Office of Epidemiology and Biostatistics, Rockville, Md., and Health Information Designs, Inc., Arlington, Va. The views expressed in this manuscript are those of the authors and do not necessarily reflect the opinion or policy of the Food and Drug Administration. Received for publication May 19, 1988. Revised Oct. 24, 1988. Accepted for publication Nov. 8, 1988. Reprint requests: B. Gerstman, DVM, MPH, PhD, Office of Epidemiology and Biostatistics, Food and Drug Administration, 5600 Fishers Lane, Room 15-42, Rockville, MD 20857. 1032
I Abbreviations COMPASS:
NPA: MDI: I
used Computerized On-line Medicaid Pharmaceutical Analysis and Surveillance System National prescription audit Metered-dose inhaler
I
I
Information about treatment of asthma on a population basis is generally lacking. Previous studies have used data obtained from selected outpatient pharmacies to determine trends and patterns of asthma treatment in the population. ‘3“3 ‘K I7 These previous studies suggest that the number of dispensed prescriptions for antiasthma drugs has increased markedly since the late 1970s and that significant changes in the relative frequency in type of drug treatment and route of administration have occurred. I53I7 In these studies, however, it has not been possible to distinguish between use of bronchodilator drugs for the treatment of asthma and other respiratory conditions. It has also been impos-
Asthma
VOLUME 83 NUMBER 6
I. Average
TABLE
yearly
prevalence
by age, sex, race, and resi’dence, Prevalence by sex
Overall Age (yr) 0 to 5 to 15 to 20 to 30to oto
in Michigan
Medicaid
1033
1980-1986
Prevalence
Prevalence residence
by race
by
Cases
COMPASS
4 14 19
6,360 6,01;!
29
2,59ll 3,550 19,977
186,932 199,821 95,668 168,635
1,463
44 44
Prevalences
116,724 767,780
are per 100 Michigan
Medicaid
Prevalence 3.4 3.0 1.5 1.5 3.0 2.6
M
F
Black
White
Other
Urban
Rural
4.2 3.7 1.7
2.5 2.3 1.4
4.9 4.6 2.2
3.0 2.4 1.3
1.7
2.3
1.4
1.6 3.1
3.5 2.3
4.3 3.8
2.8 2.3
3.8 3.4 1.7 1.8 3.5 2.9
2.1 1.7
1.0
1.9 1.7 .9 .8 1.6 1.5
METHODS Data base Data presentedin this article are derived from COMPASS (Health Information Designs, Inc., Arlington, Va.). Briefly, COMPASS is a large computerized data base of Medicaid billing data that has been developed for the postmarketing surveillanceof drugs. COMPASSdata originate from a computerized claims-processingsystem designed for fiscal and administrative control of Medicaid programs. Data are organized into patient records known as “profiles” in which Medicaid-reimbursed health care transactionsare arranged according to the date service was provided. This permits construction of medical service histories over time and enables these data to be used for postmarketing drng surveillance.‘*. I9
and operative
.7 1.7 1.5
recipients.
sible to determine the number and type of subjects treated. The present study reports trends and patterns in asthma diagnosis and treatment in the Michigan Medicaid patient population for the interval 1980 through 1986. Prevalence and frequency of drug use are determined with two different drug classification schemes. Changes in patterns of drug use, number of patients with asthma, and number of antiasthma prescriptions per patient are described.
Study population of asthma
1.0
definition
The study population was defined on a yearly basis and included Michigan Medicaid enrollees younger than 45 years that demonstrated at least one reimbursement for services in their COMPASS profile. The primary manner in which individuals in this age range become eligible for Medicaid benefits is:through the Aid to Families with Dependent Children programs. It is therefore not surprising to find that the study population primarily consistedof children and women of childbearing age (Table I). Our method of case ascertainment relied on physician and hospital billing codes suggestive of asthma diagnoses and treatments. To increasethe accuracyof distinguishing
potential casesfrom noncases, we focused on those individuals who had at least two diagnoses of asthma (International Classification of Disease, 9th revision, Clinical Modification code 493) and at least two pharmacy claims for drugs primarily used to treat asthma within their COMPASS history. With this case definition, a total of 52,231 Medicaid subjects with asthma were identified.
Monitoring
disease and drug use
To estimate the period prevalenceof asthma, profiles of the aforementioned individuals were scannedfor diagnostic and drug transactionssuggestiveof clinically active asthma. Yearly prevalencesfor the interval 1980 through 1986 were determined by age, sex, race, and residence.For the purpose of this article, Metropolitan StatisticalArea residents were considered to be “urban,” and non-Metropolitan Statistical Area residentswere consideredto be “mral.” Prevalencefor each year is reported per 100 Medicaid benefit recipients. Drug use prevalence was estimated as the proportion of subjects with active asthma reimbursed for drugs of predefined classes. The following drug classes were used: MDIs, nebulizer solutions, sodium cromolyn, sustained-releasetbeophyllines, immediate-releasetbeophyllines, fixed-combination products, oral sympathomimetic drugs, systemiccorticosteroids, and inhaled corticosteroids. Drug-use prevalencefor eachyear is reported per 100 asthma cases. In addition, drugs were classifiedaccording to their primary pharmaceuticalmode of action, ignoring route of administration and formulation type. The following mode of action classes were used: xanthines, which included sustained-releasetheophyllines, immediate-releasetheophyllines, and fixed-combination products with at least one theophylline constituent; adrenergic drugs, which included MDIs, nebulizer solutions, oral sympathomimetic drugs, and those fixed-combination products with adrenergiccomponents; and anti-inflammatory drugs, which included systemic corticosteroids, inhaled corticosteroids, and sodium cromolyn. Note that fixed-combination products are double counted as both xanthines and adrenergic drugs according to this scheme. The total and average number of Medicaid reimburse-
1034
Gerstman
et al.
01 O-4
J. ALLERGY CLIN. IMMUNOL. JUNE 1999
!
I
I
/
I
I
I
,
5-9
lo-14
15-19
20-24
25-29
30-34
35-39
40-44
Age
Males
Females -----______
FIG. 1. Average annual prevalence of asthma in subjects younger than 45 years in the Michigan Medicaid population by age and sex for the period 1980-1986.
TABLE II. Number of asthma cases, individuals in the COMPASS system, and prevalence from birth to 44 years, 1980-1986 Year
Cases
COMPASS
1980
14,698
751,231
1981 1982 1983 1984 1985 1986
17,747 20,024 22,641 23,333 21,35’7 20,036
809,467 780,140 833,317 783,308 707,916 709,087
Prevalence
2.0 2.2 2.6 2.7 3.0 3.0 2.8
ments for antiasthma drugs used by caseswas determined. Average rates of change per year were calculated by the following formula: (x,.hoY’” - 1 where %., denoteseither the prevalenceor number of events observed during the rP interval in question and xc,,)denotes the prevalenceor number of events during the first interval in question.” Although this formula may falsely assumea constant rate of change, it can, nonetheless, be useful in providing a summary statisticfor the purpose of describing trends. RESULTS Prevalence
of asthma
Average annual prevalences by age, sex, race, and residence status are listed in Table I. The prevalence
of asthma reaches its minimum at age 20 years. The prevalence of asthma was higher in male subjects younger than 20 years than in female subjects of comparable age, but was higher in female subjects older than 20 years than in male subjects of comparable age (Fig. 1). The overall prevalence was higher in black subjects than in white subjects and other races (3.8 versus 2.3 versus 1S, respectively), and was higher in urban dwellers than in rural dwellers (2.9 versus 1.5, respectively). Table II contains the number of cases, Michigan Medicaid benefit recipients in the COMPASS system, and prevalence of asthma from birth to 44 years for each of the 7 years of the study. During this interval, the prevalence increased from 2.0 to 2.8 per 100 Michigan Medicaid benefit recipients per year. This represents a 40% increase during 7 years of observation. Prevalence
of drug use
Table III contains drug use prevalence estimates by age. Overall, use of sustained-release theophylline increased at an average rate of 17% per year. A concomitant drop in the use of immediate-release theophylline occurred in all ages except from birth to 4 years in which use of this class of drug remained relatively constant. The prevalence of fixedcombination product use decreased dramatically over time, averaging a 22.3% decline per year. The use of
Asthma in Michigan
VOLUME 83 NUMBER 6
TABLE
III. Prevalence
of drug
use per 100 patients
0 to 4 Age group (VI
Drugs used Sustained-release theophylline Immediatereleasetheophylline Fixedcombination Oral sympathomimetic MDIs Nebulizer solutions Sodium cromolyn Inhaled corticosteroids Systemiccorticosteroids
with
5 to 9
1035
by age, 1980 and 1986 20 to 29
15 to 19
10to14
30 to 44
1980
1988
1980
1988
1980
1988
1980
1988
1980
1988
1980
I!388
7
48
23
55
31
60
25
59
24
59
25
63
37
39
27
20
26
10
32
8
39
10
39
11
56
5
51
7
43
8
35
10
35
10
39
16
17
49
20
38
22
29
25
19
27
24
30
27
0 1
2 9
3
19 8
9
1
56 3
19
1
47 6
16
1
1
56 4
21 3
52 6
0
6
3
8
5
7
3
3
2
3
3
3
0
0
3
4
6
7
5
7
7
8
9
11
4
8
7
10
11
13
16
19
22
25
24
30
oral sympathomimetic drugs remained constant in adults and adolescents, but demonstrated more than a doubling in patients younger than 10 years.
Overall, MD1 use increased at a rate of 22.3% per year. More than half the identified patients with asthma older than 15 years received at least one MD1 prescription in 1986. In addition, it was somewhat surprising to find that the prevalence of MD1 use in children 5 to 9 years increased from 3% in 1980 to 19% in 1986. Nebulizer solutions, inhaled corticosteroids, and sodium cromolyn were used by relatively few subjects with asthma. Systemic corticosteroid use was age related; 30-year-old patients were more than three times as likely to receive systemic steroids than subjects with asthma younger than 10 years. Overall, systemic steroid use among asthma patients increased modestly. Number
asthm.a
Medicaid
of prescriptions
Changes in the total and average number of antiasthma prescriptions per case are illustrated in Fig. 2. The total number of prescriptions doubled from just under 60,000 to nearly 120,000 per year (12.2% rate of increase per year). Simultaneously, the number of cases increased from 14,698 in 1980 to 20,036 in 1986 (Table II). Accordingly, the average number of prescriptions per patient increased from 4.07 in 1980 to 5.98 in 1986 (6.6% rate of increase per year). There was a threefold increase in sustained-release
theophylline use, a twofold increase in oral sympathomimetic prescription use, and a sixfold increase in MD1 use (Fig. 3). There was nearly a twofold decreased in fixed-combination product use and a slight decrease in immediate-release theophylline use. The number of reimbursements for nebulizer solutions, cromolyn sodium, systemic corticosteroids, and corticosteroid inhalers increased slightly. The number of Medicaid reimbursements and percent of market share by the aforementioned broad mode of action categories (see Methods section) are presented in Table IV. The number of reimbursements for xanthines peaked in 1984. There was a :steady increase in the number of adrenergic and anti-inflammatory drugs. Adrenergic and antiinflammatory drugs steadily increased market share. Comparison of Medicaid use estimates
and NPA drug
Previously reported NPA drug-use estimates (IMS America, Ltd., Ambler, Pa.) are used for comparison with Medicaid data. Since NPA data do not assess drug treatment in relation to disease, comparisons are restricted to oral bronchodilator, inhaled bronchodilator, and inhaled anti-inflammatory drug-use estimates. NPA projections suggest that the use of the drug classes in question, irrespective of indication, increased from 37 million prescriptions in 1981 to 5 1
1036
Gerstman
et al.
J. ALLERGY CLIN. IMMUNOL. JUNE 1989
/
5
4 07
4.25
11111 4 26
1980
1981
1382
4.79
5.06
5.2
1983
1954
1985
98
1986
Year PrescrIptions
per
Case
FIG. 2. Total and average number of among subjects with asthma 1980-1986.
Total
Medicaid
TABLE IV. Reimbursed prescriptions and percent year and primary pharmacologic mode of action,
Prescrmpt~ons
reimbursement
for
antiasthma
of market share within 1980 through 1986
a given
Xanthine
prescriptions
year (percent)
Adrenergic
by
Anti-inflam
Year
n
%
n
%
n
%
1980
39,950 48,264 50,726 61,075 63,221 54,461 55,468
48.8 49.1 47.7 46.9 45.8 43.8 42.0
34,153 40,370 44,343 55,129 59,753 55,155 60,298
41.7 41.1 41.7 42.3 43.3 44.3 45.7
7,808 9,580 11,235 14,158 15,124 14,852 16,250
9.5 9.8 10.6 10.9 11.0 11.9 12.3
1981 1982 1983 1984 1985 1986
Anri-infim, anti-inflammatory. Fixed combination products
are counted
as both xanthines
and adrenergic
million prescriptions in 1985.” This represents an 8.4 average annual rate of increase. During this same period, use of these drugs in the identified Medicaid population with asthma increased from 75 5 thousand prescriptions to 111.1 thousand prescriptions. This represents a 10.2% annual rate of increase. Moreover, parallel changes in market share of the considered drug classes are observed (Fig. 4). For example, sustained-release theophylline formulations accounted for 22% of the total number of prescriptions of the considered drug classes in 1981 by both NPA and Medicaid estimates. By 1985, sustained-release
drugs.
theophyllines increased to 38% and 36% of use in NPA and Medicaid estimates, respectively. Other drug classesshifted market share in consort, suggesting that trends in bronchodilator therapy in Medicaid subjects with asthma parallel that of the general population, indication of use notwithstanding. DISCUSSION Prevalence of asthma Comparisons of the asthma-prevalence estimates among various studies are difficult because of dissimilarities in case definitions and case-ascertainment
Asthma
VOLUME 83 NUMBER 6
in Michigan
Medicaid
1037
-s+SRTheo
0‘I
980
1981
1982
1983
1984
1985
-
MDI
-
POSym
-+
IRTheo
-
FComb
+
sysst
+ -.+-4
NebSol Crom InSt
1986
Year FIG. 3. Number of reimbursements for sustained-release theophylline inhalers (MD/), oral sympathomimetic drugs (POSym), immediate-release systemic steroids (SysSt), nebulizer solutions (NebSol), cromolyn products {FComb), and inhaler corticosteroids (/nSt), 1980-1986.
Percent Market Share, 1981
W?Theo), metered-dose theophylline f/RTheo), (Cram), fixed-combination
Percent Market Share, 1985
.36
36
30
30
26
26
20
20
16
16
10
10
6
6
0
SRTheo IRTheo
FComb
POwm
D&g m
Vational
(NPA)
MDI
NabSol
Cram
blst
0
SRTheo
IRTheo
FComb
@
POwm
MDI
NebSol
Croln
Drug Class
Class Medicafd
m
National
FIG. 4. Comparison of national and Medicaid drug estimates. A comparison bution of outpatient prescriptions for a selected group of antiasthma drugs, versus Michigan Medicaid asthma cases, 1981 and 1985.
methods.21.22For example, nationwide (United States) estimates of asthma prevalence, as determined by the National Center for Health Statistics, are often derived by survey questionnaire. In contrast, our method of case ascertainment relied on billing codes from health care providers for asthma-related medical transactions. In our opinion, our method is likely to be less sensitive, but more specific, than questionnaire-
INPA)
@
MedlCaid
of percent distriNPA projections
derived estimates. Therefore, it was not surprising to find that our prevalence estimates were lower than estimates of the National Center for Health Statistics for the United States as a whole.‘.“* 5 However, in spite of differences in methods and possible nonrepresentativeness of the population under study, several important patterns of disease are readily apparent. For example, decreasing prevalence
1038
Gerstman
et al.
with age during late adolescence and early adulthood followed by increasing prevalence with age during the latter half of the third decade onward has been reported.‘, 3-5, 23 The higher prevalence in male children and adolescents compared to female children and adolescents has also been widely reported.” 23-28In addition, the higher prevalence in black subjects compared to white subjects is consistent with previously published studies. *, *’ We found a higher prevalence of asthma in urban residents than in rural residents, suggesting a disparity in either disease occurrence or health care practices. Note that no adjustment has been made for race in these analyses; therefore, the apparent urban excess may partially reflec:t the unequal distribution of race in the Medicaid population, with few black subjects in the rural Medicaid population. Increases in asthma prevalence over time may reflect actual increases in prevalence or trends in diagnostic and treatment practices. In either event, increases in the number of Medicaid patients with asthma must be considered when drug use is interpreted for estimates. Drug use
Sustained-release theophylline and oral sympathomimetic drugs have replaced fixed-combination products as the preferred treatment for asthma in children. Sustained-release theophylline and MDIs have replaced immediate-release theophylline and fixedcombination products as the preferred treatment for asthma in adolescents and adults. In addition, a significant proportion of adults with asthma use systemic steroids during their course of therapy. Increasing use of oral sympathomimetic drugs in young children and use of MDIs in adolescents and adults has resulted in a general trend toward greater reliance on sympathomimetic drugs for asthma treatment (Table IV). The average number of antiasthma drug reimbursement per Michigan Medicaid asthma case increased at the rate of 6.6% lper year during the study interval. This is more than three times the rate of overall Medicaid drug reimburs’ement nationwide. (The U.S. Department of Health and Human Services reported a 2% annual growth of Medicaid drug reimbursements nationwide for the period 1973 through 1983.29) It therefore appears that the rise in antiasthma drug use is not simply an artifact of the reimbursement system. In summary, the relative and absolute occurrence of asthma and asthma treatment in the Michigan Medicaid population appears to be increasing. We expressour graritude for the programming assistance of Ms. Dede Hill, and the epidemiologic advice of Dr. Frank Lundin, Dr. Carlene :Baum, and Dr. Joel Ku&sky.
J. ALLERGY CLIN. IMMUNOL. JUNE 1989
REFERENCES 1. Evans R, Mullally DI, Wilson RW, et al. National trends in the morbidity and mortality of asthma in the U.S.: prevalence, hospitalization, and death from asthma over two decades: 1965 1984. Chest 1987;91(suppl):65S-74s. 2. Stribolt TB. Asthma. In: Bone RC, ed. Medical clinics of North America. Philadelphia: WB Saunders, 1986:909-20. 3. National Center for Health Statistics. Current estimates from the National Health Interview Survey, United States, 1982. DHHS Publication No. (PHS) 85-1578 1985:82-96. 4. Current estimates from the National Health Interview Survey, United States, 1983. Hyattsville, Md.: National Center for Health Statistics, DHHS Publication No. (PHS) 86-1582. 1986:81-96. 5. Gergen PJ, Mullally DI, Evans R. National survey of prevalence of’ asthma among children in the United States, 1976 to 1980. Pediatrics 1988;81:1-7. Fleming DM, Crombie DL. Prevalence of asthma and hay fever in England and Wales. Br Med J 1987;294:279-83. Bumey PG. Asthma mortality in England and Wales: evidence for a further increase, 1974-84. Lancet 1986;2(8502):323-6. Sinclair BL, Clark DW, Sears MR. Use of anti-asthma drugs in New Zealand. Thorax 1987;42(9):670-5. Barger LW, Vollmer WM, Felt RW, Buist AS. Further investigation into the recent increase in asthma death rates: a review of 41 asthma deaths in Oregon in 1982. Ann Allergy 1988;60(1):31-9. 10. Mao Y, Semenciw R, Morrison H, et al. Increased rates of illness and death from asthma in Canada. Can Med Assoc J 1987;137(7):620-4. 11. Jackson RT, Beaglehole R, Rea HH, et al. Mortality from asthma: a new epidemic in New Zealand. Br Med J 1982; 285:771-4. 12. Hay IF, Higenbottam TW. Has the management of asthma improved? Lancet 1987;2(8559):609-11. 13. Barbee RA. The epidemiology of asthma. Monogr allergy 1987;21:21-41. 14. Holland WW. Introduction. Chest 1987;91(suppl):65S. 15. Keating G, Mitchell EA, Jackson R, et al. Trends in sales of drugs for asthma in New Zealand, Australia, and the United Kingdom, 1975-81. Br Med J 1984;289:348-51. 16. Lanes SF, Walker AM. Do pressurized bronchodilator aerosols cause death among asthmatics? Am J Epidemiol 1987;125:75566. 17. Bosco LA, Knapp DE, Gerstman B, et al. Asthma drug therapy trends in the United States, 1972 to 1985 [Workshop]. J ALLERGY CLIN IMMUNOL 1987;80:398-402. 18. Ixssler JT, Harris BSH. Medicaid data as a source for postmarketing surveillance information. Unpublished federal document. U.S. Government Contract 223-82-3021. February 1984. 19. Strom BL, Carson JL, Morse ML, et al. The computerized on-line medicaid pharmaceutical analysis and surveillance system: a new resource for postmarketing drug surveillance. Clin Pharmacol Ther 1985;38:359-64. 20. Computer Associates. SuperCalc4 User’s Guide and Reference Manual. 2nd ed. 1986. 21. Usherwood TP. Factors affecting estimates of prevalence of asthma and wheezing in childhood. Fam Pratt 1987;4:318-321. 22. Bumey P, Detels R, Higgins M, et al. Recommendations for research in the epidemiology of asthma. Chest 1987;91 (suppl): 194S-6s. HR, Bland JM, Pate1 S, et al. The natural history 23. Anderson of asthma in childhood. J Epidemiol Community Health 1986;40(2):121-9.
Asthma in Michigan
VOLUME 83 NUMBER 6
24. Pedersen PA, Weeke ER. Epidemiology of asthma in Denmark. Chest 1987;91(suppl 6):107S-14s. 25. Smith JM. The pmvalence of asthma and wheezing in children. Br J Dis Chest 1976;70:73-7. 26. Peckham C, Butler N. A national study of asthma in childhood. J Epidemiol Community Health 1978;32:79-85. 27. Mak H, Johnston P, Abbey H, et al. Prevalence of asthma and health service utilization of asthmatic children in an inner city. J ALLERGY CLIN IMMUNOL 1982;70(5):367-72.
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28. Tuchinda M, Habananada S, Vereenil J, et al. Asthma in Thai children: a study of 2000 cases. AM Allergy 1987;59(3):20711. 29. Ruther M, Pagan-Berlucchi A, Wivell K, et al. Health Care Financing Program Statistics. Medicare and Medicaid data book, 1986, 4CFA Pub. No. 03247. Washington, D.C.: U.S. Government Printing Office, 1987:15-34.
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