Association of nutritional and environmental risk factors with Asthma among rural and urban Pre-schoolers in Mpumalanga province, South Africa

Abstract

Abstract

Background: Asthma is a significant global public health issue and one of the most common non-communicable diseases. The disease affects both young children and adults, with the majority being children in both affluent and poor nations, with the latter experiencing particularly severe consequences. The literature suggests that the disease is a complex multifactorial disorder and is largely attributed to the interactions between genetic susceptibility, characteristics of an individual and environmental exposures. The genetic factors include asthma susceptibility and genes, the characteristics of an individual include, nutritional factors including, infections and allergic sensitisation, while environmental factors include air pollution, pollens, moulds and other aeroallergens and weather. To establish recommendations to reduce the burden of asthma in this demographic group, it was necessary to evaluate its potential risk factors.

Previous studies on asthma amongst preschool children have shown that there is a limited understanding of epidemiology, incomplete risk factor analysis and a lack of comprehensive environmental assessment. Therefore, this thesis presents an observational study that examined the prevalence and risk factors associated with asthma and related symptoms among pre-schoolers.

Aim: The primary aim of this study was to observe the prevalence of asthma and its symptoms among pre-schoolers living in rural and urban areas of Mpumalanga Province, South Africa. Furthermore, the study aimed to examine the relationship between nutritional and environmental risk factors with asthma among cases and controls.

Methods: The present study was carried out in two distinct phases, namely phase one and phase two. Phase 1: An analytical cross-sectional study described and compared the prevalence of asthma and its symptoms in rural and urban Mpumalanga pre-schoolers. Parents/caregivers of preschool children (n=3145) completed a modified International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. Data were analysed using multiple logistic regression models. Phase 2 assessed two components (personal and environmental factors). An unmatched case-control study consisted of 189 pre-schoolers (63 with asthma, 126 controls) recruited from Phase 1. Firstly, the researcher identified primary dietary patterns by conducting a Principal Component Analysis (PCA) on reported food consumption data from the Quantitative Food Frequency Questionnaire (QFFQ). Anthropometric data were collected for the anthropometric status assessment using Seca scales and a stadiometer for height. Secondly, Radiello passive air samplers were utilized to measure Nitrogen Dioxide (NO2) and Sulphur Dioxide (SO2) levels at preschools to assess the indoor and outdoor air quality. Dietary patterns were analysed using PCA and were associated with asthma using multiple logistic regression. Moreover, multiple logistic regression and chi-square analysis were used to link anthropometric data to asthma. Lastly, the Wilcoxon paired signed rank test was used to compare the in/out (I/O) ratios of SO2 and NO2.

Gert Sibande District Municipality is located in Mpumalanga province and forms part of the highveld priority area, which was declared an air pollution hot spot because of poor air quality and this affects the health of communities in the area, with children being the most vulnerable group.

Results: Phase 1: The overall prevalence of wheeze ever was 15.14%, with a higher prevalence in urban pre-schoolers than rural pre-schoolers (20.71% vs 13.30 %, P<0.000). Moreover, the total prevalence of asthma ever was 2.34%. The prevalence was greater in urban pre-schoolers than in rural pre-schoolers (3.92% vs 1.81%, P<0.001). Phase 2: The results identified four primary dietary patterns that defined the dietary preferences of the pre-schoolers: meat general and dressings pattern, healthy dietary pattern, sugary and /or sweetened drinks pattern, and mixed dietary pattern. The consumption of sugary and sweetened drinks, (adjusted odds ratio (OR) 7.0, 95% CI: 2.3 -21.1; p=0.00) as well as a mixed dietary pattern, (adjusted OR 1.9, 95% CI: 1.1-3.6; p=0.03) were positively associated with a higher probability of developing asthma. In addition, being overweight was significantly linked to high chances of presenting with asthma [unadjusted Body Mass Index for Age with Z-scores (BAZ) OR 8.15 (3.97-16.71), Weight-for-age with Z- scores (WAZ) OR 5.33 (2.54-11.26), and adjusted BAZ OR 5.83 (1.21-27.89), WAZ OR 5.83 (1.21-27.89)].

The mean levels of NO2 indoors and outdoors were within the recommended criteria outlined by the World Health Organization (WHO), specifically target levels 1 (40μg.m-3) to 3 (20μg.m-3). Additionally, these values were also below those in the air quality guides outlined by South Africa, both for yearly and one-hour mean measurements. Nevertheless, both of these levels remained above the suitable threshold of 10 µg.m-3 outlined by the World Health Organization Air Quality Guidelines (WHO AQG).

Conclusion: This cross-sectional study revealed that the prevalence of wheezing and asthma was high in pre-schoolers, particularly in urban areas compared to rural areas. The case-control study further demonstrated that the consumption of sugary and sweetened drinks, as well as a mixed dietary pattern, were positively associated with a higher probability of developing asthma. Conversely, a healthy dietary pattern was found to offer protective benefits against the risk of developing asthma. The finding highlights the importance of promoting healthier eating habits for respiratory health. A comprehensive approach to asthma management is imperative, encompassing pharmacological and non-pharmacological interventions, education, and self-management components. Healthcare professionals can help children with asthma and obesity manage their condition through a combination of preventive strategies and therapeutic interventions. Some key recommendations include: prevention and lifestyle changes, medication management, weight loss through multidisciplinary intervention, nutritional counselling, routine exercise and recognition and treatment. Future research should explore the combined impact of both home and school environmental tobacco smoke (ETS), NO2 and SO2 levels on children's asthma risk and severity. This could help in understanding the overall exposure patterns and their effects on asthma development. Keywords Air quality, Dietary patterns, Anthropometric status, Overweight, Obesity, SO2, NO2, Asthma, Pre-schoolers