In our study, Puerto Rican children from the South Bronx were more likely to be born prematurely, to have mothers who smoked during pregnancy, and to have families with lower SES than island Puerto Rican children. Surprisingly, however, children living in Puerto Rico were more likely to have asthma and to have been hospitalized for asthma than Puerto Rican children living in the South Bronx.
Previous studies have demonstrated a high prevalence of asthma among children in Puerto Rico. Two separate probability sampled, community-based studies of children in Puerto Rico found the lifetime prevalence of asthma to be > 30%. Perez-Perdomo et al found that parents of island Puerto Ricans who participated in the 2000 Behavioral Risk Factor Surveillance System reported a lifetime prevalence of asthma in their children of 33.2%. While many studies have shown a high burden of asthma in mainland US cities in which a large proportion of the Hispanic population is of Puerto Rican background, fewer studies have focused on Puerto Ricans specifically.
Poverty is a common condition among Puerto Ricans-; thus, most studies of asthma in the Puerto Rican population include participants from poor and disadvantaged backgrounds. It is unlikely, however, that the high prevalence of asthma in this population can be completely explained by issues related to SES. Ledogar at al found that the prevalence of asthma was higher in Puerto Ricans than in Dominicans or “other Latinos” living on the same streets and in the same buildings in Brooklyn, NY (odds ratio [OR], 2.7; 95% confidence interval [CI], 2.0 to 3.6). Claudio et al conducted a study of 5,250 public elementary school children in New York City and found that Puerto Rican children had the highest 12-month prevalence of asthma (by parental report) of all ethnic groups, regardless of income level. Similarly, Ortega et al found no association between family income or maternal educational attainment and lifetime asthma prevalence, history of asthma attacks, or history of asthma hospitalization among children in Puerto Rico.
The finding of increased risk of asthma among island Puerto Ricans in this study was surprising for several reasons. Consistent with previous findings, premature birth (a significant risk factor for asth-ma) was more common in Puerto Rican children from the South Bronx than in those from Puerto Rico. Children from the South Bronx were also more likely to have been exposed to maternal cigarette smoking during pregnancy than children from Puerto Rico, and intrauterine smoke exposure has been associated with early wheeze, asthma, and more rapid decline in lung function. Finally, families of Puerto Rican children in Puerto Rico had a lower household income than families of Puerto Rican children living in the South Bronx but were less likely to receive public assistance. Despite the universal health insurance provided to children in Puerto Rico by the health-care reform plan of 1998 (“La Reforma”), island Puerto Rican children may have had less contact with primary health-care providers and may have been underdiagnosed with asthma. However, island Puerto Rican children may have been more likely to seek care for wheeze and cough in the emergency department, thus making them more likely than children followed up over time by a primary care physician to receive a diagnosis of asthma based on one episode of respiratory symptoms.
In contrast to our findings in Puerto Ricans, birth outside the United States has been inversely associated with asthma in Mexican Americans. In the Third National Health and Nutrition Examination Survey (NHANES III), parents were more likely to report asthma in Mexican-American children born in the United States than in Mexican-American children born in Mexico (OR, 3.2; 95% CI, 1.3 to 7.9). Holguin et al looked at 17,554 Mexican-American adults from NHANES III and the National Health Interview Survey. After adjustments for health-care access and other potential confounders, Mexican Americans born in the United States were found to be at higher risk for asthma than those born in Mexico (NHANES III: OR, 2.1; 95% CI, 1.4 to 3.3; National Health Interview Survey: OR, 2.7; 95% CI, 1.6 to 5.5). Potential explanations for the differential influence of birthplace on the risk of asthma developing among Puerto Ricans and Mexican Americans include variations in in utero or early childhood environmental exposures, sociocultural factors, or differences in migration patterns between the two groups.
There are several potential explanations for our findings that warrant further investigation. The findings of a study by Ledogar et al, in which children of different Latino backgrounds sharing the same environment had varying prevalence of asthma, suggest an underlying biological and/or genetic predisposition for asthma morbidity among Puerto Ricans. Although we found that children living in the Bronx were more likely to have at least one grandparent who was not born in Puerto Rico, there was no significant association between having all four grandparents born in Puerto Rico and an increased risk of asthma. Differences in environmental exposures are a possible explanation for a higher prevalence of asthma among island Puerto Rican children. Several studies have reported on the high prevalence of asthma in tropical environments, which may be related to ambient conditions of temperature, humidity, air pollution, as well as exposure to specific environmental allergens such as Blomia tropicalis. Blomia is the dominant dust mite species in Puerto Rico, and studies- have found high numbers of children and adults in tropical environments that have become sensitized to this allergen. In addition, although we have information on in utero smoke exposure, we do not have information on current environmental tobacco smoke exposure. In a recent school-based study of childhood asthma in Northern Puerto Rico in which 46% of elementary school participants reported a lifetime history of asthma, approximately 30% of children lived with a smoker in the house.
One potential limitation of our study is that our primary outcome measure, lifetime prevalence of asthma, is based on parental report. The question “Has your child ever had asthma?” used in this study is taken directly from the previously validated International Study of Asthma and Allergies in Childhood questionnaire,” which has been used in 56 countries and has been validated in Spanish. Of note, a similar self-reported question for adults (“Have you ever had asthma?”) has been used in the International Union Against Tuberculosis and Lung Disease Bronchial Symptoms and the American Thoracic Society Division of Lung Disease questionnaires to assess asthma prevalence, and has been shown in multiple studies to have high sensitivity and specificity in differentiating asthmatics from nonasthmatics as compared to clinical diagnosis of asthma by a physician. Moreover, the finding that island Puerto Rican children were more likely than children in the South Bronx to be hospitalized for asthma supports our results regarding asthma prevalence.
A second limitation of our study is the lack of assessment of potential confounders, including upper respiratory tract infections, bronchiolitis, family history of asthma, environmental exposures, and allergen sensitization in participating children. Two studies have examined allergen sensitization in Puerto Rican children with asthma in the United States and in Puerto Rico. Celedon et al examined skin test reactivity (STR) to aeroallergens among asthmatic children in Hartford (CT). STR to cockroach, which was found in 44% of Puerto Rican children with asthma, was associated with increased asthma severity. Among Puerto Rican children, STR to dust mite (56%) and cat dander (47%) was also common. Similar findings were reported for asthmatic children in Ponce (Puerto Rico), where STR to dust mite (88%), cockroach (40%), and cat dander (23%) was common. Future studies should examine the relation among allergen exposure, allergen sensitization, and asthma in random samples of Puerto Rican children in the US mainland and in Puerto Rico.
To our knowledge, this is the first study to compare the prevalence of asthma and asthma hospitalizations of island Puerto Rican children and Puerto Rican children from the mainland United States. Although Puerto Rican children in Puerto Rico had higher SES across multiple measures and were less likely to be born prematurely and to have mothers who smoked during pregnancy, they had significantly higher odds of ever having asthma and of having been hospitalized for asthma. Our findings suggest the need for further study of differences in asthma among Puerto Rican children in these two communities, with emphasis on differences in environmental exposures and the potential contributions of migration, acculturation, and psychosocial stressors in the development of asthma in this high-risk population.