Rural residence, farming environment, and allergic diseases in Argentinean adolescents

Abstract

Rationale Little is known about residence in a rural or farming environment and allergic diseases in Latin America. Methods Cross-sectional study of rural residence and current wheeze, current asthma and current symptoms of allergic rhino-conjunctivitis in 1,804 adolescents (ages 13–14 years) attending 31 schools in urban and rural areas of San Francisco (Córdoba, Argentina). Rural residence was classified as never, previous, and current. Duration of rural residence was categorized as 0, >0 but ≤ 5 years, and >5 years. Current wheeze, current asthma and current allergic rhino-conjunctivitis were defined on the basis of responses to an extensively validated questionnaire from the International Study of Asthma and Allergies in Childhood. Logistic regression was used for the multivariable analysis of rural residence and the outcomes of interest. Results After adjustment for current smoking and other covariates, current rural residence (odds ratio [OR]=0.15, 95% confidence interval [CI]=0.03 to 0.81) and rural residence for >5 years (OR=0.32, 95% CI=0.12 to 0.84) were significantly associated with reduced odds of current wheeze. In a multivariable analysis, current residence in a rural area (OR= 0.52, 95% CI= 0.32 to 0.86) and rural residence for >5 years (OR=0.44, 95% CI= 0.26 to 0.73) were significantly associated with reduced odds of allergic rhino-conjunctivitis. This association was no longer significant after additional adjustment for current residence in a dairy farm, which was significantly associated with reduced odds of allergic rhino-conjunctivitis. Similarly, current regular contact with farm animals was significantly associated with reduced odds of allergic rhino-conjunctivitis. Conclusions Among Argentinean adolescents, current rural residence and rural residence for >5 years were associated with reduced odds of current wheeze and allergic-rhino-conjunctivitis. These potential protective effects may be explained by a dairy farm environment, including regular contact with farm animals.

Effects of Migration on Allergic Diseases

“…Children who had migrated after 3 years of age had an increased risk of developing wheeze compared to non-migrants and migrants with less than 5 years of residence in their host city had a higher prevalence of wheeze compared to non-migrants. Another study on adolescents aged 13–14 years in an urban area of Argentina showed that the adolescents with a history of rural residence had the same rates of wheeze as compared to those who had been living in urban areas [37]. …”

Rural to urban migration is associated with increased prevalence of childhood wheeze in a Latin-American city

“… 28 Another study conducted in an urban area of Argentina showed that adolescents aged 13–14 years with a history of rural residence had the same prevalence of wheeze compared with those who had always lived in the urban area. 29 Our study focused on the effects of internal migration on wheeze prevalence in an urban population of an LMIC, where migrants formed a diverse group including migrants from rural communities, migrants from other urban settings, and those crossing voluntarily or being displaced by civil conflict across the international border with Colombia ( figure 1 ). In this setting, we found that rural to urban migration is an important determinant of a higher risk of wheeze in an urban population.…”

“…However, migrant health may deteriorate with increasing length of residence in the new country. 29 In the case of rural to urban migration, evidence for a healthy migrant effect is limited. 31 In our study, socioeconomic variables of the migrant population were not statistically different than those of the non-migrant population.…”

Antibiotic Use in Early Life, Rural Residence, and Allergic Diseases in Argentinean Children

“…This protective effect against allergic diseases may be explained by bacterial or fungal exposures resulting from contact with livestock or animal feed/shed and raw milk consumption among children living in farms 35, 36 . A few studies in Latin America have also shown rural residence to be associated with lower risk of current wheeze and allergic rhino-conjunctivitis 14, 37, 38 . In an exploratory analysis conducted as part of a study of Mexican American children, antibiotic use was associated with asthma or current wheeze in children who were born in rural areas of Mexico, but not in those born in urban areas of Mexico 39 .…”

“…In a previous study, we reported that rural residence was associated with reduced odds of current wheeze and allergic rhino-conjunctivitis among adolescents (ages 13 to 14 years) living in the province of Córdoba (Argentina) 14 . Given that finding, as well as a prior report of potential effect modification of the effect of antibiotic use on atopy by presence of animals (pets) in the home 8 , we hypothesized that antibiotic use would affect the risk of atopic diseases (current wheeze or allergic rhino-conjunctivitis) among children living in urban areas in early life, but not among those living in rural areas in early life (who are often exposed to farm animals and pets, and thus may be less susceptible to the detrimental effects of antibiotics by virtue of a richer and more robust gut microbiota).…”