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Socioeconomic Status, Drug Insurance Benefits, and New Prescriptions for Inhaled Corticosteroids in Schoolchildren With Asthma
Anita L. Kozyrskyj, PhD;
Cameron A. Mustard, ScD;
F. Estelle R. Simons, MD
Arch Pediatr Adolesc Med. 2001;155:1219-1224.
ABSTRACT
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Background Low-income children with asthma are less likely to receive inhaled corticosteroid
prescriptions that can prevent asthma morbidity.
Objective To determine whether the receipt of inhaled corticosteroids in children
with asthma is related to household socioeconomic status and type of drug
insurance.
Design Using population-based prescription and health care data from Manitoba,
a cohort study of the determinants of receiving new prescriptions for inhaled
corticosteroids was conducted in children treated with asthma drugs.
Participants School-aged children (n = 12 481) receiving asthma prescriptions
from January 1995 to March 1996 but no inhaled corticosteroid prescriptions
in the initial 6-month period.
Main Outcome Measures Household socioeconomic and drug insurance predictors of the probability
of receiving a new inhaled corticosteroid prescription from July 1995 to March
1998, following adjustment for disease and health care utilization factors.
Results In comparison with higher-income children insured through a provincial
cost-sharing drug plan, the adjusted likelihood ratio for a new inhaled corticosteroid
prescription was 0.88 (95% confidence interval, 0.80-0.97) in low-income children
insured through the same drug plan and 0.82 (95% confidence interval, 0.76-0.88)
in children receiving prescriptions at no charge through provincial income
assistance or First Nations benefits programs (Winnipeg, Manitoba).
Conclusion Independent of asthma severity, type of drug insurance, or health care
utilization patterns, low-income children with asthma are significantly less
likely to receive inhaled corticosteroid prescriptions.
INTRODUCTION
ASTHMA can cause significant disruptions in the daily activities of
schoolchildren when they must miss school or spend time in the hospital or
emergency department.1, 2 Inhaled
corticosteroids are prophylaxis drug therapies that reduce the likelihood
of asthma hospitalization.3, 4, 5, 6
They have become an integral part of asthma treatment guidelines, and their
use in children with asthma has risen during the past 10 years.7, 8, 9, 10
However, there is evidence that not all children who require inhaled corticosteroids
receive them.11, 12 Furthermore,
low-income children are more likely to have greater asthma severity and higher
asthma hospitalization rates.13, 14, 15, 16, 17
It has been increasingly documented that low-income children with asthma
are less likely to receive inhaled corticosteroid drugs, but the reasons for
this are unclear.18, 19, 20, 21, 22, 23
Although less frequent prescription drug utilization among low-income children
has been attributed to a lack of drug insurance coverage,24
less optimal use of prescription drugs has also been observed in low-income
children enrolled in drug insurance programs that provide prescriptions at
no charge.18 This study was undertaken to determine
whether the receipt of inhaled corticosteroid drugs in children with asthma
was related to their socioeconomic environment and drug insurance status.
Our hypothesis was that independent of drug insurance type, low-income children
with asthma would be less likely to receive prescriptions for inhaled corticosteroids
than higher-income children.
PARTICIPANTS AND METHODS
STUDY DESIGN
A cohort study of children with no inhaled corticosteroid prescriptions
in an initial 6-month period was nested within a population of children aged
5 to 15 years who were receiving asthma prescription drugs between January
1995 and March 1996. The rationale for selecting children taking asthma drugs
was to identify a group of asthmatic children experiencing current symptoms
who would be candidates for inhaled corticosteroid therapy.25
Children were evaluated for the receipt of a new inhaled corticosteroid prescription
during the period from July 1995 to March 1998; factors associated with the
probability of receiving an inhaled corticosteroid prescription were examined.
STUDY POPULATION
Data were obtained from 4 population-based electronic databases maintained
by the Manitoba Health Services Insurance Plan (MHSIP), which provides health
insurance for all Manitobans. The databases included (1) registration files;
(2) physician reimbursement claims; (3) hospital discharge abstracts; and
(4) records of prescriptions dispensed in retail pharmacies. The study protocol
was approved by the Human Research Ethics Board of the University of Manitoba
and the Manitoba Health Access and Confidentiality Committee, Winnipeg.
The MHSIP registration file contains a record for every individual eligible
to receive insured health services, and records birth date, sex, and geographic
location. Records of physician reimbursement for medical care provided are
submitted through a fee-for-service arrangement and contain information on
patient diagnosis at the 3-digit level of the International
Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) system. Discharge abstracts for hospital services
include information on up to 16 diagnostic codes from the ICD-9-CM, of which the first diagnosis is responsible for the hospital
stay. Prescriptions records are submitted by retail pharmacies for reimbursement
by provincial drug insurance plans and for drug utilization review purposes,
and contain data on the date of prescription dispensing, drug name and identification
number, dosage form, and quantity dispensed. The reliability and validity
of the MHSIP databases has been shown to be high.26, 27
Records linkages among databases were achieved by the use of anonymous personal
identifiers to create longitudinal histories of health care utilization. Information
on physician specialty was derived from a database characterizing Manitoba
physicians.
Children aged 5 to 15 years as of January 1995 were eligible if they
received asthma drug prescriptions between January 1995 and March 1996, according
to the following criteria: (1) at least 1 prescription for an asthma drug
(bronchodilator, inhaled corticosteroid or cromone, oral ketotifen fumarate,
or oral corticosteroid) in the presence of asthma or bronchitis diagnoses
on physician claims or hospital discharge records; or (2) in the absence of
these diagnoses, at least 1 prescription for an inhaled corticosteroid or
cromone, or a bronchodilator concomitant with ketotifen or a second bronchodilator
prescription in the next 2 years. The definition excluded children with a
singular use of bronchodilators and no asthma diagnosis.28
Limiting child age to 5 years and older decreased the likelihood of including
children with transient wheezing syndromes.29
From this population, a cohort of children with no prescriptions for inhaled
corticosteroids between January 1995 and June 1995 was selected.
STUDY MEASURES
New Inhaled Corticosteroid Prescription
The main outcome measure was the receipt of a new prescription for an
inhaled corticosteroid following 6 months of no use in children receiving
asthma drug treatment. Prescriptions included beclomethasone dipropionate,
budesonide, fluticasone propionate, flunisolide, and triamcinolone.30
Household Insurance and Socioeconomic Status
Three mutually exclusive categories of household drug insurance and
socioeconomic status were defined: (1) children insured through the provincial
income assistance or federal treaty First Nations prescription programs ("income/FN
benefits"); (2) children insured through the Pharmacare program (Winnipeg)
and living in the lowest neighborhood income quintile ("low-income"); and
(3) children insured through the Pharmacare program and living in the next
4 neighborhood income quintiles ("higher-income"). Income F/N benefits programs
provided prescription drugs at no charge. Pharmacare, the provincial drug
insurance program, provided prescription drugs on a cost-sharing basis; households
paid 100% of their prescription costs until an income-based deductible payment
had been reached. Pharmacare children were placed into income quintile neighborhoods
according to the 6-digit postal code of their household. Neighborhood income
quintiles were created from the Statistics Canada Census 1996 by aggregating
household income data within the enumeration area. Quintiles were ranked from
the 20% of the population residing in the lowest-income neighborhoods to the
20% residing in the highest-income areas. This method has been used by others
to describe neighborhood income and is a good approximation for household
income.31, 32, 33
Asthma Severity
Children were classified by level of asthma severity using a drug treatment
measure that assigned severity on the basis of the asthma prescription drug
profile and hospitalization history, as recorded in the 1995-1996 health care
data.34 Asthma severity levels were defined
as follows: mild to moderate asthma (bronchodilators with or without inhaled
corticosteroids or cromones), moderate to severe asthma (bronchodilators with
inhaled corticosteroids or cromones and/or asthma hospitalization with high
bronchodilator use [>90% of doses]), and severe asthma (bronchodilators with
inhaled and oral corticosteroids). To diminish misclassification of severity
subsequent to the nonreceipt of prescriptions, children not receiving inhaled
corticosteroids could be classified as having moderate to severe asthma if
they used high doses of bronchodilators and were hospitalized. The severity
measure was found to have good reliability ( = 0.82) and validity through
its association with markers such as hospitalization in an intensive care
unit.35
Physician Specialist Use
To adjust for physician practice style,36, 37, 38
children were classified according to use or nonuse of an asthma specialist
for care from January 1995 to March 1998. An asthma care visit was defined
as a physician visit or hospitalization for a diagnosis of asthma or for bronchitis
coexisting with a secondary diagnosis of asthma. Asthma specialists were defined
as allergists and pulmonologists; all other physicians (ie, family practice
physicians or general pediatricians) were defined as nonasthma specialists.
Continuity of Physician Care
Continuous care provided by a physician prior to the receipt of a new
inhaled corticosteroid prescription was defined on the basis of a child's
physician visit pattern by whether at least 90% of visits were to 1 nonasthma
specialist and/or 1 asthma specialist from January 1995 to March 1998 or the
date of the study outcome. Asthma drug treatment has been linked to continuity
of physician care,19, 39 and this
measure has been derived to describe continuity of primary care on the basis
of health care administrative data.40
Frequency of Respiratory Tract Infections
Because the propensity to prescribe inhaled corticosteroids is affected
by the frequency of asthma exacerbation, commonly caused by respiratory tract
infections,9, 41 the frequency
of respiratory tract infections was measured from January 1995 to March 1998
or the date of the study outcome. The measure was based on health care visits
for upper respiratory tract infections, bronchitis, or an antibiotic prescription
within 7 days of a physician visit or hospitalization for asthma. Antibiotic
use as a marker for respiratory tract infections has previously been validated.42 A respiratory tract infection visit rate higher than
the 90th percentile value was classified as a history of frequent respiratory
tract infections.
ANALYSIS
The likelihood ratio of receiving an inhaled corticosteroid prescription
from July 1995 to March 1998, or cancellation of MHSIP benefits for households
that moved out of province, was determined using Poisson regression. Following
assumptions of Poisson distribution, Poisson regression was conducted on grouped
data obtained from stratification of children by household insurance, socioeconomic
status, and other explanatory variables.43
To adjust for varying follow-up time, the rate of a new inhaled corticosteroid
prescription was based on the number of child-days, calculated from July 1995
until the date of the inhaled corticosteroid prescription, cancellation of
MHSIP benefits, or March 31, 1998. In addition to the study measures described,
the following explanatory variables were evaluated: age at study entry,44 hospitalization for asthma from birth to study outcome,45, 46, 47, 48 and
previous health care visits for asthma from birth to study outcome.47, 48 Explanatory variables were retained
in the model by comparing the difference in deviance between the nested models
with the  2 statistic for the difference in df between the 2 models at a 95% confidence interval. Sample size calculations
showed that 723 income/FN benefits children and 578 low-income children were
required to detect a likelihood ratio of 0.85 for a new inhaled corticosteroid
prescription in these children vs higher-income children. Sample size determination
assumptions included a power index of 2.96 (Bonferroni-corrected  =
.017 with a 1-tailed test; ß = .2), an incidence rate of 0.45 for inhaled
corticosteroid prescriptions, and sample size ratios of 0.11 for low- vs higher-income
children and 0.24 for income/FN benefits vs higher-income children.
RESULTS
From a population of 174 208 children aged 5 to 15 years, 16 862
met the asthma drug treatment criteria during the period from January 1995
to March 1996. Among these children, 12 481 did not receive an inhaled
corticosteroid prescription for at least 6 months after study entry. Most
children (74%) lived in higher-income neighborhoods; income/FN benefits children
accounted for 17.4% of the sample, and those living in low-income neighborhoods
represented 8.6%. Income/FN benefits and low-income children were significantly
more likely to have frequent respiratory tract infections and previous asthma
hospitalizations than higher-income children but less likely to have a prior
health care visit for asthma (Table 1).
A new prescription for an inhaled corticosteroid was documented in 40.9% of
children.
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Table 1. Proportion of Children With Characteristics Important to Receipt
of Inhaled Corticosteroids by Household Socioeconomic and Drug Insurance Status*
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Unadjusted likelihood ratios indicated that new inhaled corticosteroid
prescriptions were significantly more likely to be received by children with
more severe asthma, asthma specialist care, previous health care visits or
hospitalizations for asthma, and frequent respiratory tract infections (Table 2). Income/FN benefits children (but
not low-income children) were significantly less likely than higher-income
children to receive a new prescription for an inhaled corticosteroid. Children
with continuous physician care were less likely to receive a new inhaled corticosteroid
prescription than those without continuous care.
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Table 2. Likelihood of a New Prescription for an Inhaled Corticosteroid
by Socioeconomic and Drug Insurance Status, Asthma Severity, and Other Health
Care Utilization Factors, July 1995-March 1998*
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The likelihood ratio of a new inhaled corticosteroid prescription, adjusted
for asthma severity and asthma specialist use, was 90% for low-income or income/FN
benefits children in comparison with higher-income children (model A). The
model that best explained factors associated with the new use of an inhaled
corticosteroid contained measures of socioeconomic and drug insurance status,
asthma severity, asthma specialist use, prior asthma hospitalization or health
care, and frequency of respiratory tract infections (model B). The likelihood
of a new inhaled corticosteroid prescription was further reduced in income/FN
benefits and low-income children after adjustment for these explanatory variables.
COMMENT
Ten percent of Manitoba schoolchildren received a prescription for an
asthma drug in 1995 and 1996. Asthma practice guidelines advocate the prescribing
of inhaled corticosteroids to prevent asthma symptoms and exacerbation.7, 8 We found that 41% of the schoolchildren
treated with asthma drugs received a prescription for an inhaled corticosteroid
following a 6-month period of no use, similar to the prescribing of new courses
of inhaled corticosteroids in other populations of schoolchildren with universal
access to drug insurance.49 The extent of new
use of inhaled corticosteroids was not evenly distributed among children but
varied by household socioeconomic status and type of drug insurance. In comparison
with higher-income children, low-income and income/FN benefits children were
10% to 20% less likely to receive a new prescription for an inhaled corticosteroid.
Less frequent use of inhaled corticosteroids has been reported in low-income
children with and without access to drug insurance. Our findings in income/FN
benefits children are comparable with the observations that US children receiving
prescriptions at no charge from Medicaid are less likely than children with
private insurance to receive inhaled corticosteroid prescriptions.18, 23 However, few studies adjust for known
determinants of inhaled corticosteroid use, such as asthma severity and specialist
use20, 36, 37, 38, 50
or duration of health care for asthma and frequency of asthma triggers.9, 45, 46, 47, 48, 51, 52
As we observed, these factors were not equally distributed according to household
socioeconomic status,13, 14, 15, 16, 17, 53
and in the multivariate model, new use of inhaled corticosteroids was significantly
more likely in their presence.
Income/FN benefits households represent the lowest-income families in
Canada.54, 55 The observation that
a new prescription for an inhaled corticosteroid was less likely in income/FN
benefits children receiving prescription drugs at no charge suggests the influence
of household socioeconomic factors unrelated to issues of cost. Infrequent
use of the health care system by low-income children may result in fewer opportunities
for the prescription of inhaled corticosteroids.17, 19
Although continuous physician care was not associated with a greater likelihood
of receiving inhaled corticosteroids in our study, this may be related to
conceptual differences between a health care utilization measure and survey
measures that categorize the source of medical care as physician office vs
emergency department.39, 52 Whereas
no differences in the prescribing rate of inhaled corticosteroids have been
reported between children receiving Medicaid and non-Medicaid children, inhaled
corticosteroids are less likely to be dispensed to those receiving Medicaid.18 New receipt of an inhaled corticosteroid prescription
in our study may represent incidental use or the delayed refill of an existing
prescription. Either way, nonreceipt of inhaled corticosteroid prescriptions
may be related to parental disbelief in the effectiveness of asthma medication
in preventing symptoms, which has been associated with recurrent emergency
department use by low-income children.56, 57
Consideration of patient belief systems should be an essential component of
asthma education provided by health care professionals.58
Parental inability to pay for prescriptions remains a reason for a lower
use of inhaled corticosteroids among low-income children insured through Pharmacare.19, 59, 60, 61 This
drug insurance program is administered through an income-based deductible
payment. The payment is 2% of the annual income for households with incomes
less than $15 000 and 3% for households with higher incomes; once the
deductible level is reached, families receive their prescriptions at no charge.62 Despite access to drug insurance, deductible levels
in some low-income families may require considerable out-of-pocket payment
for expensive drugs. If asthma morbidity is to be improved, drug insurance
programs need to adjust levels of cost sharing by lowering annual deductibles
or providing 100% reimbursement for children living in low-income households.
By reporting the new receipt of prescriptions, which was unaffected
by previous prescribing practices, our objective was to represent physician
intent to prescribe inhaled corticosteroids.49
A recent study found that the prescribing of inhaled corticosteroids by physicians
in a health maintenance organization did not vary by drug insurance status
of the child.18 The prescription database contains
prescriptions dispensed, not written, and we were unable to determine whether
the nonreceipt of inhaled corticosteroid prescriptions was the outcome of
physician nonprescribing or the nonfilling of prescriptions. As others have
reported, we found that children seeing asthma specialists were more likely
to receive inhaled corticosteroid prescriptions. In comparison with general
practice physicians, the outcome of receiving care from asthma specialists
is fewer emergency department visits and hospitalizations.36, 38
These observations identify the need to educate family physicians and pediatricians
on optimal asthma drug management, an intervention that has improved outcomes
in patients with asthma.63
In conclusion, we found that independent of many influential factors,
the new receipt of inhaled corticosteroid prescriptions was less likely in
low-income children living in 2 types of households: those receiving prescriptions
at no charge and those receiving prescriptions on a cost-sharing basis. These
findings are an important contribution to the knowledge regarding the effects
of socioeconomic status on the use of asthma prophylaxis drugs in a population
with universal access to health care and drug insurance.18, 19, 20, 21, 22
The potential outcomes of lower inhaled corticosteroid use are the increased
hospitalization of low-income children,13, 14, 15, 16, 17
its associated diminished quality of life,1, 2
and higher health care costs.64, 65
In describing the role of cost and noncost dimensions of socioeconomic status,
our study has identified opportunities for intervention by drug insurance
programs as well as health care professionals.
AUTHOR INFORMATION
Accepted for publication June 7, 2001.
This research was supported by a PhD Fellowship Award from the National
Health Research and Development Program, Health Canada, Ottawa, Ontario.
What This Study Adds
Low-income children with asthma are less likely to receive prescriptions
for inhaled corticosteroids, which may or may not be attributed to cost barriers
to the acquisition of these drugs. This study was undertaken to determine
whether the receipt of inhaled corticosteroid prescriptions in asthmatic children
with access to universal health insurance was related to socioeconomic status
in households receiving prescriptions at no charge or on a cost-sharing basis.
In comparison with higher-income children, the likelihood of receiving
new inhaled corticosteroid prescriptions was reduced in low-income children
insured through a similar cost-sharing drug plan and further reduced in low-income
children receiving prescriptions at no charge. This study contributes information
on the effects of prescription cost sharing, as well as the influence of socioeconomic
factors outside of prescription cost issues on the use of inhaled corticosteroids
in low-income children with asthma.
From the Department of Community Health Sciences, Manitoba Centre for
Health Policy and Evaluation (Dr Kozyrskyj), Winnipeg; the Department of Public
Health Sciences, University of Toronto (Dr Mustard), Toronto, Ontario; and
the Department of Pediatrics and Child Health, University of Manitoba (Dr
Simons), Winnipeg.
Corresponding author and reprints: Anita L. Kozyrskyj, PhD, Department
of Community Health Sciences, Manitoba Centre for Health Policy and Evaluation,
Faculty of Medicine, University of Manitoba, S101-750 Bannatyne Ave, Winnipeg,
Manitoba R3E 0W3 (e-mail: kozyrsk{at}cc.umanitoba.ca).
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