J. Paediatr. Child Health (2004) 40, 189–194
Prevalence and correlates of paediatric asthma and wheezing
in a largely rural USA population
AA Arif,1 TF Borders,1 PJ Patterson,2 JE Rohrer1 and KT Xu1
1Division of Health Services Research, Department of Family and Community Medicine and 2Rural and Community Health Center,
Texas Tech University Health Sciences Center, Lubbock, Texas, USA
are approximately 5 million children with asthma. This cross-sectional survey sought to estimate the prevalence of asthma
and asthma symptoms and potential risk factors among children aged 16 and younger, in a largely rural population in the
This study was a telephone survey of 1500 households in the South Plains/Panhandle region of Texas. Parents
of children were interviewed with a response rate of 64%. Having been diagnosed with asthma by a physician and a report
of wheezing in the last 12 months were used as dependent variables in multivariate logistic regressions with several
sociodemographic and environmental factors as potential confounders.
The age-adjusted prevalence of asthma and wheezing among children were approximately 15 and 18%,
respectively. The prevalence of asthma was highest (20%) among children aged 11–16 (P < 0.001). Living in urban areas
was associated significantly with asthma and wheezing. Non-Hispanic blacks reported significantly increased odds of asthma
in their children (adjusted odds ratio (OR) = 2.04, 95%CI 1.02–4.08), whereas Mexican-Americans reported significantly
reduced odds of asthma (adjusted OR = 0.48, 95%CI 0.29–0.78) and wheezing (adjusted OR = 0.58, 95%CI 0.37–0.89) in
their children. The odds of asthma (adjusted OR = 1.78, 95%CI 1.09–2.92) and wheezing (adjusted OR = 2.45, 95%CI
1.52–3.95) was highest among children in the highest body mass index quartile. No significant association with pet
ownership and exposure to second-hand smoke with asthma and wheezing was observed in this study.
Urban residence, non-Hispanic black and Mexican-American race/ethnicity, and being overweight were
significantly associated with the increased risk of asthma and/or wheezing.
The prevalence of asthma among children has been increasing in the United States and it is estimated that there
asthma epidemiology; asthma; paediatric asthma; Texas.
The prevalence of asthma has been increasing, particularly
among children, in the USA. In the past two decades the
prevalence has increased more than 75%.1 According to
national estimates, the prevalence of asthma among children
ranges from 6 to 7%,2,3 affecting more than 5 million children
and it remains the leading cause of missed school days among
school-going children.4 Several studies have shown dispropor-
tionately higher morbidity and mortality due to asthma among
black children and among urban and inner-city residents.5–7
However, for reasons yet unknown, the prevalence rates are
generally reported to be lower among Mexican-Americans.8
During the 1993–1995 National Health Interview Survey,
annual age-adjusted rates of self-reported asthma were found to
be higher among blacks, those in the 5–14 year age group, and
females. Although the reason for the continually worsening
epidemiological trend of asthma prevalence remains largely
unknown, several environmental and demographic factors have
been identified, including residing in urban areas, black ethnic-
ity, sensitization to allergens, exposure to indoor and outdoor
pollutants, environmental tobacco smoke and obesity.2,5–7,9–11
We conducted a cross-sectional survey in the largely rural
South Plain and Panhandle area of Texas (West Texas), which
comprises 42 counties. The main objectives of this cross-
sectional survey were to: (i) describe prevalence of asthma and
asthma symptoms among children aged 16 years and younger
in West Texas; (ii) compare the prevalence of asthma and
asthma symptoms between urban and rural regions and among
different race/ethnic groups; and (iii) determine potential socio-
demographic and environmental risk factors of asthma among
The study was cross-sectional in design and was conducted in
the autumn of 2001. The South Plains/Pan Handle region of
Texas is sparsely settled, with only three out of 42 of its
counties considered metropolitan or urban (defined as counties
with at least 50 000 persons). Of the remaining rural counties,
18 are considered frontier areas or counties with fewer than
seven persons per square mile, and 19 are rural non-frontier.
The region is also racially diverse, with a relatively high
percentage of Hispanics. According to the 2000 Census, of the
total population in the region, approximately 50% are white,
29% are Hispanic and 17% are black/African-American.
The subjects were children aged 16 years or younger, identi-
fied by screening households in one of the 42 South Plains and
Pan Handle counties. The sample was a list-assisted random
digit-dialling (RDD) telephone sample of the area codes and
telephone exchanges in the defined geographic region. Each
phone number was called using the Sawtooth WinCATI system
(Sawtooth Technologies, Northbrook, IL, USA) until a number
Correspondence: Ahmed A Arif, MD, PhD, Assistant Professor, Texas Tech Health Sciences Center, Department Health Services Research, 3601
4th Street, Rm 1C165A, Lubbock, Texas 79430, USA. Fax: +1 806 743 1292; email: firstname.lastname@example.org
Accepted for publication 14 August 2003.
190 AA Arif et al.
had been tried at least five times or until a final disposition had
After determining age eligibility and obtaining an informed
consent, parents were interviewed in either English or Spanish
depending on subject preferences. The survey asked questions
about asthma, respiratory symptoms, general health and possi-
ble risk factors of asthma in their child. Parents also responded
to questions related to their sociodemographics, use of health
services, satisfaction with care and treatment participation.
The final sample included 1500 households at a response
rate of 64% among households known to have age-eligible
children. The study was approved by the Institutional board
The questionnaire used in this study included questions relating
to asthma and respiratory symptoms used in the questionnaire
of the International Study of Asthma and Allergies in childhood
(ISAAC).12 It was translated into Spanish, and both Spanish
and English versions were pretested before it was administered.
Demographic and socioeconomic variables included: child’s
age, child’s gender, parent’s marital status, parent’s employ-
ment status, household income, parent’s ethnicity (white,
Hispanic, black, other ethnicities), urban/rural (urban county:
population size >50 000), smoker in house, owning a pet,
homeowner (vs renter), number of people in household, par-
ent’s highest education (less than high school, high school
graduate/equivalent, 1–3 years of college, college graduate or
more), living in a house (vs mobile homes, apartment, duplex
or condominium), living within city limits and living on a farm
or ranch. The responding parents were asked about their
children’s height and weight and the body mass index (BMI)
was calculated as (weight in kg)/(height in m2). For the purpose
of this study two outcome variables were defined: (i) parent-
reported physician-diagnosed asthma (asthma); and (ii) parent-
reported wheezing or whistling in chest in the previous
12 months (wheezing). Both asthma and wheezing were used
as dependent variables in logistic models using demographic,
socioeconomic and other predictors in order to identify groups
at risk for asthma and wheezing.
Simple descriptive statistics were used to describe the study
population and compared for urban and rural groups. Preva-
lence of asthma, respiratory symptoms and potential risk
factors were computed for the total sample and for urban and
rural groups. The prevalence of asthma and wheezing were
age-adjusted to the USA projected 2000 standard population.
Stratified analyses were carried out to compare prevalence of
asthma and asthma symptoms among white, non-Hispanic
black, Mexican-Americans, Hispanics and other race/ethnic
groups of children in urban and rural settings. To compare
prevalence in different age groups, children were grouped into
three age categories: < 6 years, 6–10 years and 11–16 years.
Univariate and multiple logistic regression analysis were
used to calculate odds ratios (OR) and their 95% confidence
intervals and to explore the association between independent
variables and the outcome variable. All variables significant at
P < 0.2 in the univariate analysis were considered for inclusion
in the final model to estimate adjusted OR. Multiple logistic
regression analysis was used to adjust simultaneously for the
various independent variables. A likelihood ratio test was used
to exclude variables from the model. The Hosmer and Lame-
show goodness of fit test of the final model was assessed and an
adequate fit was obtained for the final model reported in this
paper. No significant colinearity between the various independ-
ent variables was found. All analyses were carried out using
STATA statistical software package version 7.0 (StataCorp,
College Station, TX, USA).
The characteristics of the study sample are shown in Table 1.
Of the 1500 individuals who participated in the study, 818
(54.5%) lived in urban areas and 682 (45.5%) lived in rural
areas. There were 61% non-Hispanic white, 32% Hispanic and
4% non-Hispanic black individuals who participated in the
study. The majority of Hispanics lived in rural areas, whereas
non-Hispanic blacks mostly lived in urban settings.
The prevalence rates for asthma and asthma symptoms are
shown in Table 2. The prevalence of asthma, wheezing and
exercise wheezing was significantly higher among those living
in the urban areas. When stratified by race/ethnicity, non-
Hispanic blacks in the urban areas reported a significantly
(P < 0.05) higher prevalence of asthma, exercise wheezing and
severe nocturnal wheezing (>1 night/week) as compared to
other race/ethnic groups.
Table 3 presents results of prevalence rates of asthma and
wheezing and multivariate logistic regression analyses among
children. Asthma and wheezing was significantly associated
with urban residence. Children living in urban areas had 47
and 37% increased odds of asthma and wheezing, respectively.
The prevalence of asthma was highest among children aged
11–16 years, followed by 6–10 years and <6 years (P < 0.001).
Non-Hispanic blacks reported more than two-fold increased
odds of asthma (adjusted OR = 2.04, 95%CI 1.02–4.08) in their
children as compared to non-Hispanic whites. Mexican-
Americans, however, showed significantly reduced odds of
asthma (adjusted OR = 0.48, 95%CI 0.29–0.78) and wheezing
(adjusted OR = 0.58, 95%CI 0.37–0.89). Parents with less than
a high school education reported the lowest prevalence of
asthma and wheezing in their children. However, when strati-
fied by race/ethnicity, the low asthma prevalence was observed
primarily among Mexican-American parents with less than
high school education (5.6%, P = 0.05). Non-Hispanic whites
with less than high school education reported the highest
prevalence of asthma in their children (21.7%, P = 0.002).
Overall, Mexican-Americans formed the largest group with less
than high school education; 43% compared to 35% of other
Hispanics, 5% non-Hispanic whites, 12% non-Hispanic blacks
and 16% other race/ethnic groups (P < 0.001). Interaction
between parent education level (less than high school vs high
school or more) and race/ethnicity, however, was non-significant
using a test of homogeneity (P > 0.1). Parents living in mobile
homes also reported increased odds of asthma in their children;
however, this association did not achieve statistical signifi-
cance. The presence of a cat or a dog and an exposure to
second-hand smoke (ETS) was associated with increased odds
of asthma in the univariate analysis only. The association
became non-significant after simultaneously adjusting for other
confounders in the multiple logistic regression analysis.
Approximately 18% of respondents reported the presence of
one or more smokers in the house. Blacks reported a higher
prevalence of smokers in the house (33.9%) than did whites
(18.5%), Hispanics (12.9%) and other race/ethnic groups
(15.9%, P < 0.001). A strong association of BMI with wheez-
ing was observed for both underweight (1st quartile) and
Paediatric asthma in rural USA 191
Characteristics of the study population stratified by urban/rural status
Characteristic Total % (n = 1500) Urban % (n = 818) Rural % (n = 682)
Mean ± SD
Less than high school
1–3 years of college
No. people living in house (other than reference child)
3 or more
Parent marital status
Widowed/separated or divorced
Single, never married or other
Smoker in house
Dog/cat in house
Less than $30 000
$30 000 or more
Type of home
Body mass index (child)
1st quartile (2.8–16.1)†
2nd quartile (16.1–18.9)
3rd quartile (18.9–22.5)
4th quartile (22.5–58.6)
7.60 ± 4.88
7.33 ± 4.85
7.93 ± 4.90
13.8 ± 2.4
17.6 ± 0.8
20.6 ± 1.1
29.1 ± 6.8
13.9 ± 2.4
17.5 ± 0.8
20.6 ± 1.1
29.3 ± 6.7
13.8 ± 2.3
17.6 ± 0.8
20.6 ± 1.1
28.9 ± 6.9
†Range of mean body mass index values in the respective quartiles. GED, general equivalency diploma.
Prevalence of asthma and asthma-like symptoms by urban/rural status
Symptom Total % (n = 1500) Urban % (n = 816) Rural % (n = 684)
Severe wheeze affecting speech
Dry nocturnal cough apart from cold
†Age-adjusted to the USA projected 2000 standard population.
192AA Arif et al.
overweight (4th quartile) children. However, a moderate asso-
ciation with asthma was observed for overweight (4th quartile)
This study provides the first opportunity to examine the preva-
lence of asthma and asthma symptoms in the relatively under-
studied population of West Texas. The results of the present
study show that the age-adjusted prevalence of asthma and
wheezing are approximately 15 and 18%, respectively, among
children in West Texas. The prevalence was highest in the
older age group. There is great variation in reported asthma
prevalence rates, which have ranged from less than 3% to as
high as 30% in some developed countries.13 In the United
States, the prevalence of asthma among children has increased
an average of 4.3% per year from 1980 to 1996.6 Rodriguez
et al.,2 in their analysis of the NHANES III data, reported
asthma prevalence of 6.7% among children 16 years and
younger, whereas Akinbami et al.3 reported an asthma preva-
lence of 7.4% among children aged 3–17 years in the USA.
Lanphear et al.,9 in their analysis of the NHANES III data,
reported an asthma prevalence of 6% among children <6 years
old, and 11.4% among older children.7 The prevalence of
wheezing also varies across countries and has been reported to
be as high as 30% in some countries.13 Our estimates of asthma
and wheeze prevalence are on the higher end of those reported
in the USA but within the wide range reported in other
There is widespread recognition that asthma among children
is more common in urban and inner-city areas and is more
pronounced in black children.5–7 In this study we found signif-
icantly higher prevalence of asthma and wheeze in urban areas,
especially among urban non-Hispanic black children. Several
studies have demonstrated that black children generally have
increased morbidity, increased asthma hospitalizations and
higher prevalence of asthma.2,6,14 Schwartz et al.15 reported
higher prevalence of asthma (7.2% vs 3.0%) and wheeze (9.3%
vs 6.2%) among black children as compared to white children.
Similarly, Rodriguez et al.2 reported higher asthma prevalence
among black children compared to white and Mexican-
American children. Outdoor environmental factors, which
include higher levels of nitrogen dioxide (NO2), sulphur dioxide
(SO2), and other particulate matter, may play an important role
in the increasing prevalence of asthma in urban areas.10 Several
of the established risk factors, including cockroaches and house
dust mites, are also more prevalent in urban residences.16
Hispanic Mexican-American parents reported the lowest
prevalence and significantly reduced odds of asthma and
Prevalence rates and multivariate logistic regression analysis of risk factors for asthma and wheezing in children
P-value Adjusted OR
(95% CI) for asthma
P-value Adjusted OR
(95% CI) for wheezing
Less than high school
1–3 years of college
Type of home
Dog/cat in house
Smoker in house
Body mass index (child)
0.003 1.31 (0.68–2.52)
<0.001 0.41 (0.21–0.79)
0.003 2.31 (1.43–3.73)
Fisher’s exact P-values reported for each variable. Odds ratios are simultaneously adjusted for the effects of other risk factors in the model and in
addition to child’s sex, number of people in the household and child’s cough without infection. GED, general equivalency diploma; OR, odds ratio.
Paediatric asthma in rural USA 193
wheezing in their children as compared to other Hispanic, non-
Hispanic white and black children. Carter-Pokras and Gergen,
in their analysis of the Hispanic Health and Nutrition Examina-
tion Survey (HHANES), reported a prevalence of asthma of
4.5% among Mexican-Americans as compared to 20.1%
among Puerto Rican, 9.1% among non-Hispanic blacks and
6.4% among non-Hispanic white children.8 The lower risk
of asthma among Mexican-Americans observed in this study,
however, differed by parental education status, as asthma was
more commonly observed among Mexican-American children
whose parents had received less than high school education.
This may imply underreporting by Hispanics and possibly
limited access to health care and hence deserve further
Pet ownership has been linked to asthma and asthma
symptoms in children and adults in previous studies.11,17 We
observed a 34% increased risk of asthma among children
whose parents reported owning a cat or a dog, at the univari-
ate level only. Lanphear et al.,9 in their analysis of NHANES
III data, showed that the presence of a dog in the house
accounted for 140 000 excess cases of childhood asthma in
the USA. However, recent epidemiological studies suggest
that owning a pet during early childhood may provide a
protective effect against the development of asthma.18
Whether the diminished association observed in this study
resulted from avoidance of pets by children with asthma and/
or wheezing, and hence the observed association could be an
underestimate of the true effect, or whether it reflects the
relatively new shift in thinking that pet ownership has either
protective or no effect on asthma, needs to be confirmed by
Exposure to second hand smoke, which is a strong respira-
tory irritant, was associated with increased risk of asthma in
the univariate analysis only (unadjusted OR = 1.45, 95%CI
1.01–2.08). Children who are exposed to ETS are more likely
to have asthma, increased frequency of asthma symptoms,
decreased lung functions and increased frequency of res-
piratory illnesses.19,20 In this study a high proportion of non-
Hispanic blacks reported the presence of smokers in the house,
which may have contributed to the increased risk observed
among non-Hispanic blacks.
We observed a strong association between the highest and
the lowest quartile of BMI and wheezing. The association
between the BMI and asthma was relatively modest but still
significant in the highest quartile only. Some earlier studies
have reported strong association between obesity and wheezing
among children, but failed to find significant association between
obesity and asthma.15 von Mutius et al., on the other hand,
found a significantly elevated risk of asthma in the lowest and
highest quartiles of BMI.21 Similarly, von Kries and colleagues
reported a higher asthma prevalence among overweight and
obese 5–6-year-old children.22 Our OR estimates of 1.78 for an
association between asthma and obesity are consistent with the
findings of Rodriguez et al.2 who previously reported an odds
ratio of 1.94 between asthma and BMI greater than or equal to
the 85th percentile. The relationship between asthma and
obesity is complex and has generated considerable debate. It is
possible that obesity is a result of use of corticosteroid-
containing asthma medication. It is also plausible that children
with asthma tend to spend more time indoors due to fear of
exacerbation of asthma and thereby expose themselves to a
myriad indoor pollutants that may predispose them to asthma.
Although our results are consistent with other reports and
provide further evidence of a possible causal link between
asthma and obesity, it needs to be further explored in longitudi-
There were several limitations in our study. Because our
study was cross-sectional in nature, a causal link between risk
factors and asthma/wheezing was difficult to establish. We did
not perform any indoor air sampling and therefore our findings
related to environmental risk factors may not be consistent with
other reports based on such measurements. Data on asthma/
wheezing were self-reported and we had no means to confirm
the diagnosis of asthma. However, these questions were taken
from the ISAAC study and have been validated previously in
several countries. The BMI index was based on parent-reported
height and weight. Accurate reporting of weight and height in
children is generally difficult. However, as the BMI calculated
from the self-reported height and weight among adults is
generally biased downward,23 and as there is no reason to
believe that it is different among children, our estimates of BMI
could be conservative. However, future studies with anthropo-
metric measurements are needed to validate our findings.
Finally, due to the low response rate of 64% the study may
be susceptible to the selection bias. Such bias would occur if
the responding parents who were concerned about their child’s
health were more likely to participate in the survey than the
non-respondents. Finally, differences in the practice of diag-
nosing asthma among children and variations in diagnostic
labelling could contribute to some of the variation observed in
In conclusion, the results of our study suggest a strong
association between asthma and/or wheezing, under/overweight
and several sociodemographic factors. While for the most part
our results confirm those of other studies, the differences
between this population and those in other studies may provide
hypotheses for future research. Our study, like others, demon-
strated an increased prevalence of asthma and wheezing in
urban dwellers. However, the ‘urban’ sites in this study con-
sisted of two cities with populations of approximately 200 000
persons, without major industries or environmental factors that
contribute to air pollution. In fact, air quality concerns in the
area generally are linked to agricultural chemicals and product
processing. Unlike other studies comparing rural asthma rates
to major metropolitan areas, one would not expect dramatic
urban/rural differences in air quality. The urban excess in this
study may indicate a more significant role in access to care in
the reported increased prevalence of asthma. This study pro-
vides further evidence of a potential link between asthma and
obesity. Because the prevalence of both of these conditions are
increasing rapidly among children in the USA, the public
health and medical care implications are significant. The inter-
actions between asthma and BMI deserve further study.
The authors wish to acknowledge the financial support pro-
vided by the Texas Tech University Health Sciences Center
Office of Rural and Community Health and thank Dr Sharon
Meyers for reviewing this manuscript.
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