Prevalence of asthma and other allergic conditions in Colombia 2009–2010: a cross-sectional study

There is data from epidemiological studies, mostly from middle and high income countries, that suggests the disease burden due to asthma may have stabilized or even decreased [1]‐[3]. It is not clear, however, if the same tendency would be observed in low to middle income countries, or by that matter, for allergic rhinitis (AR) and atopic eczema (AE) as well [4]‐[6]. Additionally, “new” associations, potentially causal, may keep disease burden increasing in different regions [7]‐[13].

Given the potentially inaccurate inferences when extrapolating research findings from different countries, especially on allergic conditions where the “drivers” of risk may be substantially different and vary dramatically among regions of the same country [14], it is crucial to have national estimates of epidemiological trends in these conditions. This is particularly important in Latin America, where the diversity of environmental conditions is high [15]. Colombia is a country of over 41 million inhabitants, predominantly urban (72%), where about 30% live in the four largest cities (Bogota, Medellin, Cali and Barranquilla). Similar to other countries in the Andean region (Venezuela, Ecuador, Peru, Bolivia), Colombia is experimenting changes consistent with a society in transition, with an aging population, where the main causes for death are chronic diseases. Colombia´s GIP, life expectancy, mortality rates and other basic health indicators are closer to those of Peru and Ecuador [16].

For Colombia, while previous research on asthma and other allergic conditions can serve as a good base for comparisons [5, 6, 17]‐[19], there is limited information available for both adults and children simultaneously on the current burden and impact of allergic conditions. This is the case as well for many Latin American countries, and certainly for those in the Andean and Caribbean regions.

The objectives of this study were to estimate the current prevalence of asthma, AR, AE and atopy in six colombian cities; to quantify costs to the patient and her/his family; and to determine levels of Immunoglobulin E (IgE) in asthmatic and healthy subjects.

We obtained information on 5978 subjects (Table 1). In the school-based phase, 40.9% of schools, randomly selected, participated. In the community-based phase, participation ranged from 40%-70% between cities. In the nested case–control study, 53.4% of eligible case and 15.5% of eligible controls participated. The frequency of the“does not know/does not respond” option varied, but was below 3% for all questions in the questionnaire.

This cross-sectional study describes the prevalence of asthma, AR and AE symptoms in six Colombian cities, as well as their severity and burden. It provides as well the prevalence of atopy in asthmatic subjects, and in subjects without these conditions. The study is important because it is able to provide this information in subjects between 1 and 59 years of age. Additionally, this study is uniquely poised to generate vital surveillance information in Colombia, and increases the understanding of the public health burden due to these conditions in developing countries.

The current study used the same questions as the ISAAC initiative worldwide, and was conducted in the same cities in Colombia as a previous study from the same research group eleven years ago [17]. However, differences in age groups, methods and in data analysis, as well as in allergens used for sIgE, preclude a formal comparison between the two surveys, or with others conducted previously in Colombia and abroad. Thus, contrasts discussed here can only suggest potential tendencies over time. Our study suggests that the prevalence of symptoms of all three conditions is increasing in Colombia. This tendency towards an increase is similar to that found in ISAAC studies over an average of 8 years in the region; for the 13–14 age group, Latin America was one of the few regions in the world (with Africa) that had more centres increasing prevalence of all three diseases simultaneously [4]. The wide variations observed in this study in the prevalence of the three conditions, as well as those observed between cities and for the different age groups, have been found previously elsewhere [24], as well as for Latin American countries [25]. These differences suggest that local factors may dramatically alter the prevalence of these conditions, and they can include a wide number of both genetic and environmental characteristics acting simultaneously and synergistically. The study by Mallol et al [25] that included three cities in Colombia (Bogota, Cali, Barranquilla), did not find a positive associations between asthma and the socioeconomic variables studied (latitude, altitude, national gross income, poverty). The Isaac III study in Bogota, however, found that asthma symptoms were correlated with the presence of a cat in the home, higher maternal education, watching televison 1 to 2 hours per day, and the use of acetaminophen and antibiotics in the last year [18]. In that same study, rhinoconjunctivitis symptoms were associated with previous acetaminophen and antibiotic use, and higher maternal education and cesarean birth [26]. Additional risk factors in Latin America have also been postulated and described in detail by Cooper et al elsewhere [27, 28].

The prevalence of current asthma symptoms (12%) seems to have increased in Colombia with respect to results obtained 11 years ago (10%) [16]. The age group where asthma symptoms where most frequent in both surveys is the 1–4 year old group. It is likely that some of these symptoms correspond to wheezing episodes associated with respiratory viral infections early in life [29]; recent evidence, however, also suggest that bronchial obstruction during acute respiratory infection in childhood is clearly associated with subsequent asthma, especially among school-aged children at risk for repeated asthma exacerbations [30], making it relevant to quantify and to include in epidemiological studies. In the current survey we found an increase in current asthma symptoms for those subjects 5–17 years of age. In the ISAAC I-III 13–14 age group, similar increases were found in Latin America for Mexico, Costa Rica, Panama, Chile, and Argentina [4].

Disease severity for asthma remains high when compared with results 11 years ago. This may be due to under-diagnosis of asthma; in both surveys, the frequency of physician diagnosis is very low when compared to symptom-based prevalence, especially for subjects below age 18 years of age, suggesting limited access to specialized health care in these age groups. Suboptimal asthma control can be another explanation for persistent disease severity, due to lack of general physician awareness on current guidelines on effective treatment strategies for asthma [31, 32]. Disease burden to the patient and the caregiver was important in our study, with more of 60% of asthma patients reporting out-of-pocket expenses. Inappropriate ambulatory care of subjects with asthma can also be associated with increased hospitalization due to exacerbations; asthma is an ambulatory care sensitive condition where the need for hospitalization can be a marker of inappropriate health care [33]. Additionally, the mean number of days lost from work or school is our study is consistent with moderate persistent asthma, a stage of severity associated with substantial health care costs and hospitalizations in previous studies in the literature [34, 35].

While the presence of asthma independent of increased IgE levels is not uncommon [36], the majority (60%) of subjects with asthma symptoms in the past year met the criteria for atopy in our study. This is lower than the frequency obtained in the previous study in 1999 (76%), but still high. The frequency of atopy may vary between regions and countries, which is expected because it depends on environmental and genetic factors [37]. There were statistically significant differences in atopy between cases and a control group in our study. In our population, the high frequency of atopy among controls may be explained in part because of exposure to helminths, mainly Ascaris lumbricoides infections, early in life [38]. Nematode exposure induces specific IgE responses and increases total IgE levels. In the tropics, permanent exposure to mite allergens and parasite infections during childhood may induce sIgE to cross-reacting allergens from mites and Ascaris[39, 40].

The prevalence of AR symptoms also seems to have increased with respect to the previous study (from 23% to 32%) [17], but with a modest increase compared to a more recent survey in three Colombian cities that used the same ISAAC methodology during 2002 [41]. The larger increase in AR symptoms (than that seen for asthma symptoms) is in line with the ISAAC I-III comparisons in Latin America, where more centres had an increase for AR than for asthma [4]. With 28% current prevalence of rhinoconjunctivitis in children 5–17 years old (data not shown), Colombia would be among the countries in the region with the largest prevalence, as detected by ISAAC methodology [4, 6, 41]. Similarly, the prevalence of AE symptoms (14%) increased markedly in comparison to results obtained 11 years ago (4%). The current prevalence of AE symptoms has increased as well when compared with results obtained for Colombia during 2002 in the 6–7 and 13–14 year old population [5].

Our study has limitations. First, results may not be extrapolated to children not attending school or living in rural dwellings in Colombia. Second, the community-based strategy was not random and selection bias is possible if subjects willing to participate were also more likely to have one of the conditions under study, biasing results towards higher disease prevalence. While we do not have information on non-participants to evaluate this possibility, we used a systematic approach to select eligible and consenting neighboring households, and subjects within households were randomly selected. Third, our choice of controls to assess differences in atopy (excluding those with allergic rhinitis and atopic eczema) can be questioned; while such exclusions may have biased the prevalence of atopy in the control group below that in the source population of cases, we believe that exclusion of these two conditions provide a better estimate of the prevalence of atopy in the population sampled. Fourth, given that we used two allergens to diagnose atopy by sIgE (extracts from D. pteronyssinus and B. tropicalis), it is possible that the effects of cross reacting antibodies were more relevant. Differences of allergen sensitization between patients and controls could have been greater if we had included other allergens of interest, such as Dermatophagoides farinae, but financial limitations and the population-based design precluded this.

Our results show that in contrast to more affluent countries [42]‐[44], these allergic conditions are a significant problem in urban cities in Colombia, that severity of asthma is substantial, and that levels of atopy are highly associated with asthma symptoms. Since the allergic component of asthma seems to be important, consideration should be given to its evaluation during diagnosis. Additionally, results of this work support the increasing evidence that the prevalence of asthma and other allergic diseases in Latin America is high [26], even though the climate and hygiene conditions are different than those of industrialized countries. Future research in the field should look for common risk factors acting at different times in developed and developing countries.