Discussion
In this GAN survey of adolescents in South Africa, we found a prevalence of current wheeze (13.7%) higher than the global average (10.4%) but lower than that reported in a more urban population in Cape Town.5 Despite a high burden of asthma in our population, inhaled medication use, particularly with ICS, was only 1%, a finding illustrating gaps in asthma care shared by many LMICs, including India.18
The rural-urban difference in severe asthma seen in the mixed model analysis is in keeping with several studies in LMICs.19 One of these, a Ugandan study, found a strong rural-town-city risk gradient among school children aged 5–7 years.20 Those born in a small town or the city had an increased asthma risk compared with those born in rural areas (2.16 (1.60 to 2.92)) and (2.79 (1.79 to 4.35)), respectively. While farming and exposure to livestock have been suggested to have a protective effect on the development of asthma in HICs, this is not so pronounced in LMICs, where rapid urbanisation coupled with exposure to environmental pollution and lifestyle changes may have a dominating causal effect.19
Using school quintiles as a proxy for SES, we found that children from fee-paying schools had a higher asthma prevalence and more severe asthma symptoms. Although this proxy reflects a population-level measure, our findings represent a different perspective on the influence of economic status on asthma prevalence and severity. Urban lifestyle factors like diet, obesity and traffic pollution may increase with improving SES and are emerging targets for interventions that would impact asthma outcomes.7 21
Providing access to ICS is key to improving the quality of care for asthma in LMICs, where affordable drugs would reduce the burden on health systems and people affected by asthma.2 Despite the socioeconomic differences in this population, access to diagnosis and treatment remains poor overall. Even with better access to inhaled therapy in more affluent children, its incorrect use may negate its effect. A notable difference between socioeconomic groups was seen in health-seeking behaviour, with the underprivileged having less access to doctors and emergency and healthcare facilities. Similar to an asthma cohort in Zimbabwe, this could reflect poor access due to limited resources.22 However, their preference for alternate care in managing uncontrolled asthma symptoms, including traditional healer visits and use of alternative treatment was highlighted and requires further probing in South Africa and other LMICs.22 23
Furthermore, in adolescents with severe asthma, those with younger siblings were more likely to lack diagnosis. A possible explanation is that viral infections, more frequent in younger siblings, may exacerbate their adolescent sibling’s asthma symptoms, who may repeatedly and suboptimally be treated for the viral illness rather than diagnosed with asthma. Also, some adolescents with severe asthma symptoms received inhalers but not a diagnosis. In this setting, diagnosis of asthma and adherence to asthma guidelines is a critical gap in asthma management, as ICS and diagnostic guidelines are available in the primary care setting in South Africa.24 Strategies to increase access to basic effective asthma care, including non-physician-led optimisation of inhaled medicines and individualised education, are feasible and impactful in LMICs.25
The recent key step change of asthma management to include ICS whenever a SABA is taken or ICS-LABA with symptoms remains a challenge in LMICs.3 26 Similar to our South African cohort, SABA overuse/overreliance is still commonly reported in sub-Saharan Africa (sSA).3 27 Of concern is the high proportion of adolescents who are still prescribed oral asthma treatments against local guidelines.24 Studies across Africa show that people with asthma symptoms generally prefer oral medication and are reluctant to use inhaled asthma treatment.28 29 Strategies leading to better adherence and asthma control, including education, can dispel myths, reduce stigma and improve perceptions and attitudes around asthma and asthma treatments.25 Furthermore, the lack of clinical trial evidence from LMICs perpetuates their inability to appropriately inform decision-making and asthma healthcare.18
Exposure to outdoor pollution was significantly associated with asthma symptoms in the study, consistent with other African studies.8 30 However, these could be limited by biased traffic reporting, where those who may have symptoms and are aware of the risks of traffic pollution may report increased truck exposure. There is little data on air pollution and its effects on asthma in our setting. In Durban, 52% of children living in a highly polluted factory district reported asthma symptoms in the preceding 12 months.31 Similarly, self-reported rates of wheeze in the last 12 months (37%) in school-going children residing in a highly polluted area in Durban were strongly correlated with school absence.32 Increasing urbanisation, poor air quality and traffic pollution in emerging cities have been directly correlated to respiratory illnesses, including chronic obstructive pulmonary disease (COPD) in adults and asthma symptoms in children.30 33 An increasing number of air pollution interventional studies conducted in LMICs mainly address indoor biomass exposures, and these have not shown efficacy in reducing morbidity and mortality in children.34 35 Moreover, many air pollution studies rely on macroenvironment markers of exposure and give little insight into precise microenvironment measurements of pollutants such as black carbon and particulate matter.36
Self-reported smoking was similar across affluent and non-affluent schools and reflected previous literature as a significant risk factor for current and severe asthma.37 Environmental tobacco smoking (ETS), a well-established cause and trigger for asthma, is also a leading risk factor for COPD, a major cause of morbidity and mortality in sSA.2 Furthermore, ETS exposure in asthmatic individuals has been associated with worse lung function, more asthma exacerbations and greater usage of emergency care services.38 There is a need to understand the determinants of adolescent smoking in this setting to enhance antitobacco messaging and policy making, particularly as smoking increases the odds of COPD by twofold.2
In our cohort, higher SES and urban lifestyle appear to be associated with severe asthma and higher morbidity. Similarly, American inner-city children with asthma were significantly more overweight than controls.39 40 Interestingly, adolescents in this study who were primarily on a western diet significantly contributed to most hospital visits for respiratory symptoms. Contrasting a recent South African cohort, a Western diet did not increase the likelihood of current or severe asthma in our population.41 However, this observation is in keeping with a systematic review, where although no relation between risk of incidence or prevalence of asthma was found in 70 000 individuals, there was an association between severe asthma symptoms and a Western diet.42
In our cohort, the likelihood of current and severe asthma increased by at least twofold and threefold with eczema and rhinoconjunctivitis. While atopy-associated asthma is more prevalent in countries with the highest economic status, a rural-urban difference has been noted in Africa with increased sensitisation in urban children.43
The current study is limited as a questionnaire-based survey that relies on self-reporting (which may be influenced by recall and language) instead of objective markers for confirming asthma and exposures. However, the GAN questionnaire is a standardised and globally implemented instrument based on the methodology of ISAAC, which has concurrent and predictive validity.12 Indoor exposures including pets, particularly birds contribute to symptoms of eczema, rhinitis and allergic asthma. However, the GAN questionnaire elicits the presence of cats and dogs only. Similarly, the GAN questionnaire does not elicit health seeking practices including use of alternative treatments and traditional healers. As no additional tool was used, this information cannot be included in our study and is a limitation. Furthermore, the epidemiological nature of the study precludes our ability to identify causal relationships with certainty. However, these are useful for establishing preliminary evidence for a causal relationship between asthma, severe asthma and atopy. Our study had strengths as the study participants were representative of the population of school-going children in KZN who are primarily rural. Despite a disparity in number, participants from rural and urban areas were represented in the study.
In conclusion, asthma is common in South Africa. Severe asthma symptoms are underdiagnosed and associated with atopy, environmental, lifestyle and dietary factors. Where there is a diagnosis, inhaler treatment remains underused with SABA overreliance. Solutions geared at long-term follow-up focusing on asthma education and issuing appropriate medication for symptom control may be beneficial in LMICs. A World Health Assembly resolution to ensure access to asthma medicines, such as that with other non-communicable diseases, including Diabetes Mellitus, will ensure all asthmatics access to affordable, quality-assured ICS.