Asthma, a global public health problem , affects over 6.8 million children and adolescents in the United States . There is profound variability in the prevalence and morbidity of asthma among ethnic groups .
Ethnicity is strongly correlated with socioeconomic status (SES) in the United States, where members of certain ethnic groups (e.g. African-Americans, Puerto Ricans) are disproportionately represented among the poor. Because poverty has been associated with increased asthma morbidity, it has been postulated that SES is solely responsible for ethnic differences in asthma and asthma morbidity. The effect of SES on illnesses such as asthma is likely mediated through pathways including environmental exposures, access to healthcare, stress, and psychological/cultural factors . However, ethnicity is also correlated with racial ancestry, which may influence asthma disparities through differences in the frequency of disease-susceptibility alleles.
The purpose of this article is to review current evidence to support the role of SES and other factors as potential explanations for ethnic-related differences in asthma, and to suggest potential future directions for research in this field.
Asthma and asthma morbidity in ethnic minorities
The prevalence, morbidity, and severity of asthma are higher in children who belong to certain ethnic minorities [5,6], and/or whose households report indicators consistent with low SES [7••,8]. Although the overall prevalence of current childhood asthma in the United States is 8.7%, it varies widely by ethnicity, ranging from 4 to 5% in Asian-Indians and Chinese to 19% for Puerto Ricans, with non-Hispanic whites and other minorities ranking in the middle [2,3,9•,10•] (Table 1). Similarly, the rate of current asthma in children from families below the federal poverty threshold is higher (11.1%) than in families above it (7.7–8.5%) [10•]. Asthma severity is higher in certain ethnic groups such as Puerto Ricans and African-Americans . African-Americans have more emergency room visits, hospitalizations, and higher mortality rates from asthma than whites . In contrast to the low mortality rates from asthma among Mexican-Americans (0.3 per 100 000), mortality among Hispanics in New York City, which has a large proportion of Puerto Ricans, is approximately 1.3 per 100 000 [12••].
We will review the main mechanisms and potential factors underlying the association between SES, ethnicity, and asthma.
Many environmental factors influence the pathogenesis and severity of asthma.
Compared to rural areas and suburbs, indoor allergen levels are higher in urban households in low-income areas and in those hosting multiple families [13•,14]. Inner-city households have higher levels of indoor allergens such as cockroach, which are associated with increased asthma morbidity. Differences in allergic sensitization among ethnic groups are more pronounced in inner-city environments. Using data from inner-city children in the Third National Health and Nutrition Examination Survey (NHANES III), Stevenson et al.  found that Mexican-Americans were three times more likely and that African-Americans were four times more likely to be sensitized to cockroach than whites (after adjustment for age, sex, and indicators of SES factors). Children with asthma who live in the inner city also tend to have more emergency room visits for asthma than their counterparts from rural regions .
Residence in inner-city areas partly explains the high levels of exposure of certain ethnic minorities to high levels of indoor allergens . Two studies of asthmatic children in the US northeast showed that Hispanic and African-American ethnicity are associated with reduced exposure to high levels of dust mite allergen but increased exposure to cockroach allergen, even after accounting for indicators of SES [16,17]. Potential explanations for the observed association between ethnicity and indoor allergen exposure include residual confounding by housing characteristics and/or behavioral differences among ethnic groups. Although a nationwide survey showed no association between ethnicity and dust mite allergen levels in the beds of US homes, it was limited by small sample size and thus had inadequate statistical power .
Ethnicity has been associated with patterns of allergic sensitization (atopy) in children with and without asthma. African-American and Puerto Rican children (with and without asthma) are more likely to be sensitized to cockroach and dust mite than white children . Because African-Americans have been shown to be exposed to relatively low levels of dust mite allergen, this finding suggests ethnic differences in susceptibility to sensitization to specific allergens.
Although most children with asthma are atopic, a significant proportion of atopic children do not have asthma. This dissociation between atopy and asthma varies by ethnicity. For example, Mexican-Americans have a similar prevalence of atopy but a lower prevalence of asthma than Puerto Ricans. Determinants of ethnic differences in susceptibility to asthma in atopic children have been largely unexplored.
Approximately 20% of US adults smoke  with significant variation by SES: smoking prevalence is approximately 46% in people with a General Education Development (GED) diploma, 22% for those with a college education, and approximately 7% for persons with a graduate degree. Smoking is also more prevalent among people living below the federal poverty level (31%). Smoking rates vary widely among ethnic groups, with American-Indians and Alaska Natives having the highest rates at aproximately 32%, and Asians the lowest at 10%. Despite marked differences in asthma prevalence and morbidity, African-Americans and whites have similar rates of cigarette smoking (approximately 22–23%). Among 12–17-year-olds participating in a survey from 1999 to 2001, reported smoking rates were 28% for American-Indians/Alaska Natives, 16% for whites, 11% for Hispanics, and 7% for non-Hispanic blacks .
Prenatal and postnatal exposures to cigarette smoking are associated with asthma and asthma morbidity in childhood [21•]. In-utero smoke exposure varies widely among ethnic minorities: 20% in American-Indians, 16% in whites, 10% in Puerto Ricans and non-Hispanic blacks, 5% in Japanese, 3% Mexicans, and 1.5% in Central/South Americans . In-utero smoke exposure also varies by insurance type and education status .
During childhood, the prevalence of tobacco smoke exposure and levels of salivary cotinine are higher in children with asthma symptoms and doctor-diagnosed asthma, with a more pronounced difference in children from lower SES [24•]. Smoke exposure increases asthma morbidity; conversely, smoke-free laws have been associated with fewer asthma emergency room visits both in children and in adults [25•].
Smoking behavior among adults varies with ethnicity and SES, with members of certain ethnic groups (e.g. Puerto Ricans) smoking more often and/or more heavily than members of other groups (e.g. Mexicans). Thus, differences in parental smoking could account for part of the observed ethnic disparities in childhood asthma. However, few studies have tried to assess the effects of smoking on ethnic differences in asthma. In a study of over 9000 people, Beckett et al.  found that an association between Hispanic origin (mainly Puerto Rican) and increased risk of asthma was not influenced by passive exposure to smoking at home.
Outdoor pollutants can trigger asthma exacerbations and may play a role in asthma pathogenesis. Nonwhites are more likely to live in areas with elevated levels of air pollutants, including particulates, carbon monoxide, ozone, and sulfur dioxide [27,28••]. A study in New York City showed higher rates of asthma exacerbations and hospitalizations in children from highly polluted areas such as the Bronx, which also has a high percentage of residents from minority populations .
Nitrogen oxide and diesel exhaust particles (DEP), markers of traffic-related air pollution, have also been associated with increased asthma symptoms [30••]. Recent data suggest that the effect of DEP may be modified by genetic polymorphisms: in a cohort of children in Cincinnati, high DEP exposure was associated with increased risk of wheezing only in carriers of allele Val(105) in the gene for glutathione S-transferase π (GSTP1) .
Access to healthcare
Access to healthcare is determined by several factors, which in turn influence asthma morbidity.
Household income and insurance status
In a study of over 100 000 children (the National Survey of Children's Health), Flores and Tomany-Korman [32••] found marked differences between ethnic groups with regard to full-time employment rates, household income, and insurance coverage and type. In that study, the prevalence of asthma was higher in ethnic groups with relatively low employment rates, income, and insurance coverage (Fig. 1). In New York City, asthma ‘hotspots’ correspond to areas with higher concentrations of ethnic minorities, low-income households, and public housing .
Lack of adequate health insurance has a negative impact on asthma management by imposing barriers to appropriate diagnosis and treatment [28••]. Recent advances in both long-term and acute asthma management may exacerbate such inequality, as they would only be accessible to those with adequate insurance. It should be noted, however, that lack of access to healthcare is unlikely to be the sole explanation for ethnic differences in asthma outcomes. For example, Puerto Ricans, who are US citizens, have greater morbidity from asthma than Mexican immigrants in spite of easier access to healthcare.
Stress and comorbidities
Exposure to stress/violence and co-existing illnesses such as obesity and depression may partly explain the ethnic differences in asthma that are mediated by SES.
Exposure to stress and violence
Long-term maternal stress in early life has been associated with increased risk of childhood asthma, independently of other factors such as low SES [34•]. Cohen et al. [35••] recently reported that physical or sexual abuse was associated with current asthma morbidity in a cross-sectional study of Puerto Rican children. Family structure also plays a role, with children living with a single mother at higher risk for inadequate management of and increased morbidity from asthma [36•]. Together with results from other recent studies [37•,38•,39], these findings suggest that exposure to stress and violence (which is more common in ethnic minorities) influences the pathogenesis and morbidity of asthma in childhood.
Obesity has been associated with asthma in different populations [40,41•]. Among asthmatics in the Childhood Asthma Management Program (CAMP), the proportion of overweight was higher in blacks and Hispanics than in whites and in members of other races [42•].
The influence of obesity on asthma could be due to several factors, many of which are associated with SES (e.g. diet and exercise). However, it has been reported that increased adiposity in infancy is associated with recurrent wheeze later in childhood [43•]. This points towards other mechanisms such as genetic factors or a general inflammatory state [44••], which could predispose to airway inflammation. Severe obesity further impairs airflow due to increased chest wall resistance. Patients with obstructive sleep apnea (OSA) and habitual snoring not only have obstructive problems but also tend to have increased airway inflammation at baseline . Several adipokines (cytokines produced by adipose tissue) have been implicated in airway inflammation [46•].
Depression and anxiety
Depression and anxiety are more prevalent in youth of lower SES  and/or with limited education . Adolescents with asthma have nearly twice the risk of depressive or anxiety disorders as adolescents without asthma [49•]. In a large population-based birth cohort in Finland, depressive symptoms and emotional behavioral problems before 8 years of age were associated with asthma in early adulthood . Whether preceding or accompanying asthma, there is a clear relationship between depression and increased symptom report, poor medication adherence, and increased school absenteeism [51•]. Finally, comorbid depression/anxiety are under-recognized and undertreated in youth with asthma .
Psychological and cultural factors
Parental psychological and cultural factors may affect childhood asthma in several ways. Parents of black and Hispanic children worry more about their child's asthma but have lower expectations for symptom control and functionality, more competing priorities, and more concerns about overmedication and medication dependency than white parents [53••]. They also tend to have worse compliance with preventive medications, even when insurance coverage is not an issue . Similar results have been elicited in individuals of South Asian descent and in other minorities in the United Kingdom [55•]. Among adolescent asthmatics in the US, minority and low SES patients were more likely to have an inaccurate perception of their asthma control, with an evident tendency toward underperception of symptoms .
Physicians' attitudes and perceptions also play a role. Among a large sample of adult asthmatics, African-Americans were more likely to have their asthma severity underestimated by treating physicians, resulting in less inhaled steroids usage, and less instruction on exacerbation management [57•]. Similar findings have been reported with minorities in the Netherlands , where universal healthcare is available.
Beyond socioeconomic status
We have reviewed several mechanisms by which SES may influence asthma, particularly in ethnic minorities. However, factors correlated with SES are unlikely to explain all the variability in asthma prevalence, severity, and mortality among ethnic groups .
- Non-Hispanic blacks have a higher prevalence of current asthma, exacerbations, and hospitalization rates than whites even after adjusting for several demographic and socioeconomic factors .
- Puerto Rican children have higher and Asian children lower asthma prevalence and hospitalization rates than whites, even after adjusting for sociodemographic variables .
- Mexican-Americans have lower asthma prevalence than most other groups, yet tend to have incomes and insurance coverage similar to that of African-Americans and Native Americans; they are also more likely than whites, and almost as likely as African-Americans, to be sensitized to indoor aeroallergens .
All of the above findings could be explained by residual (unmeasured) confounding by factors related to SES (e.g. housing characteristics, exposure to stress, and violence). However, in a survey of over 3000 individuals in almost 1000 homes in the same area in Brooklyn (NY), Ledogar et al.  found that ethnic differences in asthma prevalence (5% in Dominicans vs. 13% in Puerto Ricans) were not influenced by residence (cluster or building), education level, country of education, or household size. This is a thought-provoking study, as differences in asthma prevalence were present in ethnic groups sharing very similar environments and SES within a same geographic area.
A potential explanation for part of the observed ethnic disparities in asthma is genetic predisposition. The heritability of asthma has been reported to be between 36 and 79%, and several groups have identified genomic regions and/or genes potentially implicated in the pathogenesis and/or severity of asthma [61••]. Although some of these studies have included members of ethnic minorities (e.g. African-Americans, Hispanics, and Asians) most have been conducted in non-Hispanic whites. As an example, results for studies of three candidate genes for asthma are listed in Table 2. Whereas there are potential asthma-susceptibility genes, none has been consistently replicated across all major ethnic groups.
Ongoing genome-wide association studies (GWAS) have identified and will continue to identify asthma-susceptibility genes. Ethnic differences in the effect of a disease-susceptibility gene were recently reported in a GWAS of diabetes mellitus type II [72•]: of relevance, the observed differences were likely due to variation in allelic frequencies by ethnicity, as well as potential interactions between genetic variants and unmeasured environmental factors. Thus, recent findings suggest that well conducted GWAS of asthma in ethnic minorities (including examination of gene-by-gene and gene-by-environment interactions) should provide valuable insights into the causes of ethnic disparities in asthma.
Differences in SES among ethnic groups are likely to influence ethnic disparities in asthma morbidity through several mechanisms. An improved understanding of these SES-related pathways is essential and could lead to a reduction in current asthma disparities. However, the interactions between these factors are very complex and difficult to dissect and thus comprehensive policies that address SES disparities as a whole should help reduce the asthma burden in ethnic minorities.
Although vigorous efforts to address SES-related risk factors for asthma are essential and should continue, we must also recognize the importance of understanding the impact of genetic variation and its interaction with environmental exposures on asthma pathogenesis in ethnic minorities.
This work was supported by grants HL04370, HL066289, HL079966, HL073373, and T32 HL07427 from the National Institutes of Health.
References and recommended reading
Papers of particular interest, published within the annual period of review, have been highlighted as:
• of special interest
•• of outstanding interest
Additional references related to this topic can also be found in the Current World Literature section in this issue (p. 183).
1 Asher MI, Montefort S, Bjorksten B, et al
. Worldwide time trends in the prevalence of symptoms of asthma, allergic rhinoconjunctivitis, and eczema in childhood: ISAAC phases one and three repeat multicountry cross-sectional surveys. Lancet 2006; 368:733–743.
2 Trends in Asthma Morbidity and Mortality. New York: American Lung Association; 2007 [updated 2007; cited 2008 October] Available from: http://www.lungusa.org
3 Akinbami LJ. The state of childhood asthma, United States, 1980–2005. Hyatsville, MD: National Center for Health Statistics; 2006.
4 Wright RJ, Mitchell H, Visness CM, et al
. Community violence and asthma morbidity: the inner-city asthma study. Am J Public Health 2004; 94:625–632.
5 McDaniel M, Paxson C, Waldfogel J. Racial disparities in childhood asthma in the United States: evidence from the National Health Interview Survey, 1997 to 2003. Pediatrics 2006; 117:e868–e877.
6 Bai Y, Hillemeier M, Lengerich E. Racial/ethnic disparities in symptom severity among children hospitalized with asthma. J Healthcare Poor Underserved 2007; 18:54–61.
7•• Cope SF, Ungar WJ, Glazier RH. Socioeconomic factors and asthma control in children. Pediatr Pulmonol 2008; 43:745–752. This interesting study shows SES influences asthma control status, in a setting with universal healthcare coverage, even after adjusting for healthcare utilization and controller medication usage.
8 CDC. QuickStats: percentage of children aged <18 years who currently have asthma by race/ethnicity and poverty status, National Health Interview Survey - United States, 2003–2005. MMWR Morb Mortal Wkly Rep 2007; 56:99.
9• Brim SN, Rudd RA, Funk RH, Callahan DB. Asthma prevalence among US children in underrepresented minority populations: American Indian/Alaska Native, Chinese, Filipino, and Asian Indian. Pediatrics 2008; 122:e217–e222. This study looks at differences in asthma prevalence in several ethnic minorities in the US by race, region, place of birth, income, and insurance coverage.
10• Moorman JE, Rudd RA, Johnson CA, et al
. National Surveillance for Asthma: United States, 1980–2004. Morb Mortal Wkly Rep Surveill Summ 2007; 56:18–54. This is a comprehensive study on the epidemiology of asthma in the US over the last 25 years, both in children and adults.
11 Ramsey CD, Celedon JC, Sredl DL, et al
. Predictors of disease severity in children with asthma in Hartford, Connecticut. Pediatr Pulmonol 2005; 39:268–275.
12•• Cohen RT, Celedón JC. Asthma in Hispanics in the United States. Clin Chest Med 2006; 27:401–412. Very comprehensive review on the status of asthma in Hispanics in the United States, including prevalence, morbidity, risk factors, and management.
13• Salo PM, Arbes SJ, Crockett PW, et al
. Exposure to multiple indoor allergens in US homes and its relationship to asthma. J Allergy Clin Immunol 2008; 121:678–684. This study looks at the role of indoor allergens on asthma exacerbations, as well as risk factors for increased allergen exposure.
14 Stevenson L, Gergen P, Hoover DR, et al
. Sociodemographic correlates of indoor allergen sensitivity among United States children. J Allergy Clin Immunol 2001; 108:747–752.
15 Simons E, Curtin-Brosnan J, Buckley T, et al
. Indoor environmental differences between inner city and suburban homes of children with asthma. J Urban Health 2007; 84:577–590.
16 Leaderer BP, Belanger K, Triche E, et al
. Dust mite, cockroach, cat, and dog allergen concentrations in homes of asthmatic children in the northeastern United States: impact of socioeconomic factors and population density. Environ Health Perspect 2002; 110:419–425.
17 Kitch BT, Chew G, Burge HA, et al
. Socioeconomic predictors of high allergen levels in homes in the greater Boston area. Environ Health Perspect 2000; 108:301–307.
18 Arbes SJ Jr, Cohn RD, Yin M, et al
. House dust mite allergen in US beds: results from the First National Survey of Lead and Allergens in Housing. J Allergy Clin Immunol 2003; 111:408–414.
19 CDC. Cigarette smoking among adults, United States 2006. MMWR Morb Mortal Wkly Rep 2007; 56:1157–1161.
20 CDC. Prevalence of cigarette use among 14 racial/ethnic populations, United States 1999–2001. MMWR Morb Mortal Wkly Rep 2004; 53:49–52.
21• Goodwin RD, Cowles RA. Household smoking and childhood asthma in the United States: a state-level analysis. J Asthma 2008; 45:607–610. The authors find an association between household smoking and an increased risk of childhood asthma at the state level in the United States.
22 Mathews TJ. Smoking during pregnancy in the 1990s. Maryland: National Center for Health Statistics; 2001.
24• Delpisheh A, Kelly Y, Shaheen R, Brabin BJ. Salivary cotinine, doctor-diagnosed asthma and respiratory symptoms in primary schoolchildren. Matern Child Health J 2008; 2008:188–193. This interesting study found that salivary cotinine levels are higher in asthmatic children and lower in SES households.
25• Rayens MK, Burkhart PV, Zhang M, et al
. Reduction in asthma-related emergency department visits after implementation of a smoke-free law. J All Clin Immunol 2008; 122:537.e3–541.e3. In this very interesting study, authors found a significant reduction in the age-adjusted rate of ED visits for asthma after implementation of a smoke-free law.
26 Beckett WS, Belanger K, Gent JF, et al
. Asthma among Puerto Rican Hispanics: a multiethnic comparison study of risk factors. Am J Respir Crit Care Med 1996; 154(4 Pt 1):894–899.
27 O'Connor GT, Neas L, Vaughn B, et al
. Acute respiratory health effects of air pollution on children with asthma in US inner cities. J All Clin Immunol 2008; 121:1133.e1–1139.e1.
28•• Shanawani H. Health disparities and differences in asthma: concepts and controversies. Clin Chest Med 2006; 27:17–28. Very interesting review on health disparities using asthma as a model, looking at biological and socioeconomic factors.
29 Maantay J. Asthma and air pollution in the Bronx: methodological and data considerations in using GIS for environmental justice and health research. Health Place 2007; 13:32–56.
30•• Jerrett M, Shankardass K, Berhane K, et al
. Traffic-related air pollution and asthma onset in children: a prospective cohort study with individual exposure measurement. Environ Health Perspect 2008; 116:1433–1438. In this interesting study, authors find that increased levels of traffic pollution are associated with a significantly higher risk of incident asthma.
31 Schroer KT, Myers JM, Ryan PH, et al.
Associations between multiple environmental exposures and glutathione S-transferase P1 on persistent wheezing in a birth cohort. J Pediatr 2008.
32•• Flores G, Tomany-Korman SC. Racial and ethnic disparities in medical and dental health, access to care, and use of services in US children. Pediatrics 2008; 121:e286–e298. This is a very comprehensive study looking at several measures of health and healthcare use including asthma among ethnic minorities, and their association with socioeconomic and sociodemographic factors.
33 Corburn J, Osleeb J, Porter M. Urban asthma and the neighbourhood environment in New York City. Health Place 2006; 12:167–179.
34• Kozyrskyj AL, Mai X-M, McGrath P, et al
. Continued exposure to maternal distress in early life is associated with an increased risk of childhood asthma. Am J Respir Crit Care Med 2008; 177:142–147. This is an interesting study, in which authors find that long-term maternal stress during childhood is associated with asthma in their children by 7 years of age.
35•• Cohen RT, Canino GJ, Bird HR, Celedon JC. Violence, abuse, and asthma in Puerto Rican children. Am J Respir Crit Care Med 2008; 178:453–459. In this attention-grabbing study, childhood physical or sexual abuse is associated with increased asthma prevalence, healthcare use, and medication use.
36• Chen AY, Escarce JJ. Family structure and the treatment of childhood asthma. Med Care 2008; 46:174–184. This study looks at the relationship between living in single-parent homes or homes with several children and measures of asthma control such as office visits and medication refills.
37• Turyk ME, Hernandez E, Wright RJ, et al
. Stressful life events and asthma in adolescents. Pediatr Allergy Immunol 2008; 19:255–263. Authors found an association between stressful events and increased asthma morbidity in adolescents, after adjusting for several sociodemographic factors.
38• Subramanian SV, Ackerson LK, Subramanyam MA, Wright RJ. Domestic violence is associated with adult and childhood asthma prevalence in India. Int J Epidemiol 2007; 36:569–579. This study shows increased childhood and adult asthma in patients exposed to or experiencing domestic violence in India.
39 Jeffrey J, Sternfeld I, Tager I. The association between childhood asthma and community violence, Los Angeles County, 2000. Public Health Rep 2006; 121:720–728.
40 Sithole F, Douwes J, Burstyn I, Veugelers P. Body mass index and childhood asthma: a linear association? J Asthma 2008; 45:473–477.
41• Jacobson JS, Mellins RB, Garfinkel R, et al
. Asthma, body mass, gender, and Hispanic national origin among 517 preschool children in New York City. Allergy 2008; 63:87–94. This study suggests there is an association between race, body mass index, sex, and asthma status in young children.
42• Bender BG, Fuhlbrigge A, Walders N, Zhang L. Overweight, race, and psychological distress in children in the childhood asthma management program. Pediatrics 2007; 120:805–813. In this study, there was an increased prevalence of overweight risk among a cohort of asthmatics, when compared to the general population.
43• Taveras EM, Rifas-Shiman S, Camargo CA Jr, et al
. Higher adiposity in infancy associated with recurrent wheeze in a prospective cohort of children. J Allergy Clin Immunol 2008; 121:1161–1166. In this study the authors found that increased adiposity at 6 months of age is associated with increased risk of recurrent wheezing at 3 years of age.
44•• Litonjua AA, Gold DR. Asthma and obesity: common early-life influences in the inception of disease. J Allergy Clin Immunol 2008; 121:1075–1084. This is a detailed review on early factors that can influence the comorbidity between asthma and obesity, such as genetics, prenatal exposures, maternal diet, sedentary behaviors, and so on.
45 Verhulst SL, Aerts L, Jacobs S, et al
. Sleep-disordered breathing, obesity and airway inflammation in children and adolescents. Chest 2008; 134:1169–1175.
46• Kim KW, Shin YH, Lee KE, et al
. Relationship between adipokines and manifestations of childhood asthma. Pediatric Allergy Immunol 2008; 19:535–540. Interesting study looking at different cytokines secreted by adipose tissue and their possible relationships with asthma.
47 Lemstra M, Neudorf C, D'Arcy C, et al
. A systematic review of depressed mood and anxiety by SES in youth aged 10–15 years. Can J Public Health 2008; 99:125–129.
48 Bjelland I, Krokstad S, Mykletun A, et al
. Does a higher educational level protect against anxiety and depression? The HUNT study. Soc Sci Med 2008; 66:1334–1345.
49• Katon W, Lozano P, Russo J, et al
. The prevalence of DSM-IV anxiety and depressive disorders in youth with asthma compared with controls. J Adolescent Health 2007; 41:455–463. In this study, the authors find that youth with asthma have a significantly higher comorbidity with depression and anxiety than healthy controls.
50 Goodwin RD, Sourander A, Duarte CS, Niemela S. Do mental health problems in childhood predict chronic physical conditions among males in early adulthood? Evidence from a community-based prospective study. Psychol Med 2009; 39:301–311.
51• Bender B, Zhang L. Negative affect, medication adherence, and asthma control in children. J Allergy Clin Immunol 2008; 122:490–495. In this longitudinal study, self-reported negative affect in asthmatic children was associated with decreased asthma control.
52 Katon WJ, Richardson L, Russo J, et al
. Quality of mental healthcare for youth with asthma and comorbid anxiety and depression. Med Care 2006; 44:1064–1072.
53•• Wu AC, Smith L, Bokhour B, et al
. Racial/ethnic variation in parent perceptions of asthma. Ambulatory Pediatrics 2008; 8:89–97. One of the very few studies that addresses the issue of parental perception of pediatric asthma symptoms and morbidity, as well as expectations of health in their children.
54 Lieu TA, Lozano P, Finkelstein JA, et al
. Racial/ethnic variation in asthma status and management practices among children in managed medicaid. Pediatrics 2002; 109:857–865.
55• Smeeton NC, Rona RJ, Gregory J, et al
. Parental attitudes towards the management of asthma in ethnic minorities. Arch Dis Child 2007; 92:1082–1087. Interesting study in which authors report cultural differences in the understanding of asthma and asthma medications among minorities in the UK.
56 Rhee H, Belyea MJ, Elward KS. Patterns of asthma control perception in adolescents: associations with psychosocial functioning. J Asthma 2008; 45:600–606.
57• Okelo SO, Wu AW, Merriman B, et al
. Are physician estimates of asthma severity less accurate in black than in white patients? J Gen Intern Med 2007; 22:976–981. In this though-provoking study, the authors find that physicians are more likely to underestimate asthma symptoms in black patients when compared to whites.
58 Urbanus-van Laar JJN, de Koning J, Klazinga N, Stronks K. Suboptimal asthma care for immigrant children: results of an audit study. BMC Health Services Res 2008; 8:22.
59 Ledogar RJ, Penchaszadeh A, Garden CC, Iglesias G. Asthma and Latino cultures: different prevalence reported among groups sharing the same environment. Am J Public Health 2000; 90:929–935.
60 Claudio L, Stingone JA, Godbold J. Prevalence of childhood asthma in urban communities: the impact of ethnicity and income. Ann Epidemiol 2006; 16:332–340.
61•• Scirica CV, Celedon JC. Genetics of asthma: potential implications for reducing asthma disparities. Chest 2007; 132(5 Suppl):770S–781S. Very thorough review looking at the results and limitations of various genetic studies in different ethnic minorities, including candidate genes, linkage, and association studies.
62 Howard TD, Postma DS, Jongepier H, et al
. Association of a disintegrin and metalloprotease 33 (ADAM33) gene with asthma in ethnically diverse populations. J Allergy Clin Immunol 2003; 112:717–722.
63 Raby BA, Silverman EK, Kwiatkowski DJ, et al
. ADAM33 polymorphisms and phenotype associations in childhood asthma. J Allergy Clin Immunol 2004; 113:1071–1078.
64 Lind DL, Choudhry S, Ung N, et al
. ADAM33 is not associated with asthma in Puerto Rican or Mexican populations. Am J Respir Crit Care Med 2003; 168:1312–1316.
65 Hersh CP, Raby BA, Soto-Quiros ME, et al
. Comprehensive testing of positionally cloned asthma genes in two populations. Am J Respir Crit Care Med 2007; 176:849–857.
66 Su D, Zhang X, Sui H, et al
. Association of ADAM33 gene polymorphisms with adult allergic asthma and rhinitis in a Chinese Han population. BMC Med Genet 2008; 9:82.
67 Lee JH, Park HS, Park SW, et al
. ADAM33 polymorphism: association with bronchial hyper-responsiveness in Korean asthmatics. Clin Exp Allergy 2004; 34:860–865.
68 Tsai HJ, Shaikh N, Kho JY, et al
. Beta 2-adrenergic receptor polymorphisms: pharmacogenetic response to bronchodilator among African American asthmatics. Hum Genet 2006; 119:547–557.
69 Choudhry S, Ung N, Avila PC, et al
. Pharmacogenetic differences in response to albuterol between Puerto Ricans and Mexicans with asthma. Am J Respir Crit Care Med 2005; 171:563–570.
70 Hunninghake GM, Soto-Quirós ME, Avila L, et al
. Polymorphisms in IL13, total IgE, eosinophilia, and asthma exacerbations in childhood. J Allergy Clin Immunol 2007; 120:84–90.
71 Kang MJ, Lee SY, Kim HB, et al
. Association of IL-13 polymorphisms with leukotriene receptor antagonist drug responsiveness in Korean children with exercise-induced bronchoconstriction. Pharmacogenet Genomics 2008; 18:551–558.
72• Yasuda K, Miyake K, Horikawa Y, et al
. Variants in KCNQ1 are associated with susceptibility to type 2 diabetes mellitus. Nat Genet 2008; 40:1092–1097. Although not related to asthma, this study exemplifies why it is important that genetic studies be done in different ethnic populations, given that genotypic associations may vary substantially from one group to another.