Abstract
Background
There is a paucity of information that characterized the burden of asthma in the Eastern Sub-Saharan African (ESSA) region. Therefore, this study estimated the prevalence of asthma and its premature mortality in the region from 1990 to 2023.
Methods
Data on the prevalence of asthma and the years of life lost (YLL) were extracted from the Global Burden of Diseases 2023 database for the ESSA region. Asthma prevalence was estimated using disease modelling with a Bayesian meta-regression tool (DisMod-MR 2.1), whereas YLLs were derived using the Cause of Death Ensemble model (CODEm). The Comparative Risk Assessment Framework was applied to identify the risk factors for years of life lost. The spatiotemporal Gaussian process regression technique (ST-GPR) was used to smooth the trend. Age-standardized rates as well as the percentage change between 1990 and 2023 were estimated.
Results
There were an estimated 20,716,738 prevalent cases (95% UI: 16,523,031-26,057,565) of asthma in the ESSA region in 2023, with an age-standardized rate of 4,324 cases per 100,000 population (95% UI: 3,555-5,261). There were an estimated 918,517 years of life lost (95% UI: 582,476-1,379,986) in the region and 297 age-standardized years of life lost per 100,000 population (95% UI: 221-487). No inter-country variations were estimated throughout the region. However, the YLLs rate increased with age. Occupational asthmagens, high body-mass index, sexual violence against children, and tobacco use were the leading risk factors for asthma-related premature mortalities in the region, with variable impacts by countries.
Conclusion
There were high and persistent rates of morbidity and premature mortality from asthma in the ESSA region from 1990 and 2023. Targeted strategies are urgently needed to mitigate asthma risk factors and improve disease management.
Keywords
Background
Asthma is a heterogeneous, chronic respiratory disease characterized by fluctuating expiratory airflow limitation because of inflammation or bronchial smooth muscle constriction. 1 There were an estimated 3,416 prevalent cases of asthma per 100,000 population (95% UI: 2,899-4,066) globally in 2019, which resulted in 274 disability-adjusted life years per 100,000 population (95% UI: 217-343). 2 The disease distribution varies significantly by socio-demographic conditions, location, and other comorbidities, including cardiovascular diseases, chronic obstructive pulmonary disease, chronic rhinosinusitis, and obstructive sleep apnea.1,3
The Global Initiative for Asthma has developed a new strategy for 2024, recommending asthma prevention measures, including addressing modifiable risk factors, practicing effective clinical case management, and enhancing research and training activities. 1 Several countries in the Eastern Sub-Saharan African (ESSA) region have aligned their asthma prevention and management strategies with these global recommendations.4,5 However, regional trends of the disease remain unreported. This highlights a critical evidence gap to inform public health decision-making.
This study analyzed the prevalence, premature mortality (i.e., measured by the years of life lost (YLLs)), and attributable-risk factors of asthma by sex, age, and countries in the ESSA region from 1990 to 2023, using the data, methods, procedures, and tools of the Global Burden of Diseases (GBD) 2023 study. The findings are believed to contribute to developing targeted asthma prevention policies, efficient resource allocation, and enhancing inter-country collaborative efforts.
Methods
Study setting
This study was conducted in the ESSA region, encompassing Burundi, Ethiopia, Comoros, Kenya, Madagascar, Djibouti, Malawi, Eritrea, Mozambique, Rwanda, Tanzania, Zambia, South Sudan, Somalia, and Uganda.
Study nature
The study utilized the GBD 2023 estimates to determine the prevalence of asthma and its premature mortality. The GBD 2023 study performed a comprehensive assessment of the magnitude and burden of 375 diseases or injuries and 88 risk factors by sex and age across 204 countries and territories from 1990 to 2023. It was the single largest and most detailed scientific effort coordinated by the Institute for Health Metrics and Evaluation (IHME) with over 20,000 global researchers (https://www.healthdata.org/research-analysis/gbd).
Participants
The GBD estimates were produced by using all available data sources in the ESSA region from 1990 to 2023. The study included individuals of all ages and both sexes. Data that could not be reclassified from garbage codes were excluded. Moreover, all data sources that lacked the required metadata, such as age, sex, location, or year, were also excluded from this study to ensure comparability, validity, and representativeness.
Identification of asthma cases
The GBD 2023 study identifies and defines asthma cases using a standardized, epidemiological modeling approach designed to allow comparisons across different sexes, ages, times, and countries. An asthma case was defined based on the combination of clinical history, recent symptoms, and medication use.
Data sources
The study used the GBD 2023 estimates, which were publicly available at: https://vizhub.healthdata.org/gbd-results/. The input data sources comprised surveillance data, health information systems, and cause-of-death records. 6
Statistical analyses
This study employed the methodological framework, procedures, and analytical tools of the GBD 2023 study, following the Guidelines for Accurate and Transparent Health Estimates Reporting (GATHER).
7
Asthma prevalence was estimated using disease modeling with a Bayesian meta-regression tool (DisMod-MR 2.1), which generated internally consistent estimates of disease prevalence by reconciling cause-specific and all-cause mortality within the hierarchical structure of the GBD cause classification.
8
YLLs were estimated in the Cause of Death Ensemble model (CODEm), which employed a combination of statistical models based on their out-of-sample predictive validity. Multiple iterations of out-of-sample predictive validity were assessed for each model, and those with the lowest root-mean-square error were assigned greater weight in constructing the final ensemble model. The Comparative Risk Assessment Framework (CRAF) was applied to identify the risk factors for YLLs. The spatiotemporal Gaussian process regression technique (ST-GPR) was used to smooth the trend across locations from 1990 to 2023. Age-standardized rates were produced to adjust for variations in population size and age structure. All rates were reported per 100,000 population. The 95% uncertainty intervals (UIs) were derived from the 2.5th and 97.5th ranked values of 1,000 draws of the posterior estimates. The overall reduction or increase in rates over the entire study duration, 1990-2023, was calculated by comparing the values at the start and end of the period, using the following formula:
Results
Prevalence
Prevalence and YLLs from asthma, and annualized rate of change by sex in the ESSA region, 1990 to 2023.
Age and sex distribution of the prevalence rate of asthma in the ESSA region, 2023.
Age-standardized prevalence rate of asthma in the ESSA region, 1990 to 2023.
Years of life lost
There were an estimated 918,517 YLLs from asthma (95% UI: 582,476-1,379,986) in the ESSA region in 2023, with 489,175 YLLs among males (95% UI: 281,839-799,279) and 429,342 YLLs among females (95% UI: 199,104-718,718). This was equivalent to an estimated 297 YLLs per 100,000 population (95% UI: 221-487), with 319 YLLs per 100,000 females (95% UI: 150-542) and 274 premature deaths per 100,000 males (95% UI: 218-551). There was no significant difference in the YLLs rate by sex and location. However, the rate of YLLs increased with age among both sexes. Between 1990 and 2023, the rate remained unchanged across the region. Moreover, the trend didn’t change among children aged <20 years and adults aged 20+ years (Table 1, Figures 3 and 4). Age and sex distribution of YLLs rate due to asthma in the ESSA region, 2023. Age-standardized rate of YLLs from asthma in the ESSA region, 1990 to 2023.
Attributable risk factors associated with asthma-related premature mortalities
Occupational asthmagens constituted the primary contributor to asthma-related YLLs in the ESSA region as well as in Burundi, Ethiopia, Kenya, Madagascar, Mozambique, Rwanda, Somalia, South Sudan, Uganda, and Tanzania. They ranked as the second leading contributor in Comoros, Eritrea, Malawi, and Zambia, and the third in Djibouti. High body-mass index emerged as the predominant contributor to asthma-related YLLs in Comoros, Eritrea, Malawi, Zambia, and Djibouti, while representing the second most important contributor in the region and across Burundi, Ethiopia, Kenya, Madagascar, Mozambique, Rwanda, Somalia, South Sudan, Uganda, and Tanzania. Tobacco smoking ranked third among the causes of asthma-related YLLs in the ESSA region and in Burundi, Madagascar, Mozambique, Rwanda, Somalia, South Sudan, Uganda, Tanzania, Malawi, and Zambia. In Ethiopia, Kenya, and Eritrea, sexual violence against children was identified as the third leading risk factor of asthma-related YLLs. Secondhanded smoke was the second leading contributor to asthma-related YLLs in Djibouti and the third in Comoros (Figure 5). The leading causes of the age-standardized rate of YLLs from asthma in the ESSA region, 2023.
Discussion
This study estimated the prevalence of asthma and its premature mortality in the ESSA region from 1990 to 2023, using data and methods of the GBD 2023 study. The study revealed that 20,716,738 individuals were living with asthma (95% UI: 16,523,031-26,057,565) in the region in 2023, with an age-standardized rate of 4,324 cases per 100,000 population (95% UI: 3,555-5,261). This resulted in 918,517 YLLs (95% UI: 582,476-1,379,986), with the age-standardized rate of 297 YLLs per 100,000 population (95% UI: 221-487). There were no inter-country variations in the prevalence and YLLs rates by sex and location throughout the region. However, the rate of YLLs increased with age among both sexes. Moreover, the rates remain unchanged in 2023 compared to the rates in 1990. Occupational asthmagens, high body-mass index, sexual violence against children, and tobacco use were the leading risk factors for asthma-related premature mortalities in the region, with variable impacts by country.
The age-standardized prevalence rate of asthma was 4,324 cases per 100,000 population (95% UI: 3,555-5,261) in the ESSA region in 2023. This estimate is comparable to that reported in 2021, which may reflect minimal changes in asthma-related risk factors between 2021 and 2023. The rate is similar to those of the Western Sub-Saharan African region but higher than that of Southern, Central Sub-Saharan African, Northern African, and Middle Eastern regions.9,10 However, it is lower than the rate estimated in North America, the Caribbean, and Australasia, which a combination of underdiagnosis, environmental differences, and lower rates of urbanization could drive. More specifically, in many parts of sub-Saharan Africa, limited healthcare infrastructure, lack of diagnostic tools, and a shortage of trained specialists lead to a high underdiagnosis rate. Moreover, the urbanization rate in the ESSA region is lower than in developed regions. Urban environments are strongly associated with higher levels of outdoor air pollution and increased exposure to indoor allergens, which are key drivers of asthma.11,12 These results emphasize the critical need to strengthen healthcare systems in the region to improve asthma prevention and management, reduce disease burden, and decrease premature mortality.
The age-standardized YLLs rate from asthma was 273 per 100,000 population (95% UI: 218-551) in the ESSA region in 2023, which was lower than the rate in the Northern Africa and the Middle East region. 13 Moreover, the premature mortality increased by 64.1% in the Northern Africa and Middle East regions between 1990 and 2019. 13 The findings likely reflect complications associated with asthma and coexisting chronic respiratory diseases. There is a need to revise the existing intervention strategies to prevent asthma in the region to reduce the premature mortality from asthma. The elevated premature mortality in those regions may be attributed to greater exposure to occupational asthmagens, high body-mass index, and ambient particulate matter pollution.14,15 This finding underscores the need to tackle these risk factors to reduce premature mortality.
The prevalence and YLLs rates from asthma remain unchanged throughout the region between 1990 and 2023, except for slight changes in the prevalence rate in Uganda and Kenya. This could be due to underdiagnosis, environmental risk factors like urbanization and smoking, unavailability of drugs, suboptimal case management, and poor quality of life.16–18 These imply that asthma is a hidden burden resulting from underdiagnosis, misclassification, risk factors, and suboptimal management. Hence, preventing exposure to risk factors, promoting healthy lifestyles, strengthening diagnostic capacity, treating cases early, ensuring equitable resource allocation, and fostering collaboration between countries in the region are deemed necessary to reduce the prevalence and premature mortality.
In the ESSA region, premature death from asthma increased with age for both sexes. This could be explained by persistent exposure to environmental risk factors, a high prevalence of uncontrolled asthma, and insufficient long-term therapy. More precisely, elderly persons who use firewood, dung, and agricultural leftovers for cooking and heating in houses with inadequate ventilation may experience severe attacks. Furthermore, many individuals may have uncontrolled asthma due to poor medication adherence, a dependence on short-acting remedies rather than inhaled corticosteroids, and a lack of routine medical follow-ups. Delays in obtaining medical attention during an attack are more common in older persons, which raises the chance of death.19,20
There is a need to revise asthma prevention and management strategies in the ESSA region, as regional estimations indicated a high and unchanged burden of asthma from 1990 to 2023. In the region, the prevalence rate of asthma was higher than the YLLs rate, suggesting a substantial hidden burden of morbidity that puts a high burden on public health services. According to this scenario, asthma is a common chronic illness that is frequently misdiagnosed and inadequately treated, resulting in long-term suffering, low quality of life, lost productivity, and absenteeism from work rather than sudden mortality. Therefore, long-term, primary care-based management must take precedence over acute, emergency-only care in policy. Instead of treating asthma only in tertiary settings, this calls for educating healthcare professionals on how to correctly identify and treat the condition and incorporating asthma care into primary health systems.16,21,22
However, the low death rate is misleading because many patients have poorly managed symptoms as a result of a significant overreliance on fast-acting bronchodilators and limited access to inhaled corticosteroids. Policies must ensure affordable, reliable access to essential asthma medications. High asthma prevalence is linked to occupational exposure to asthmagens, high body mass index, sexual violence, and tobacco use in the ESSA region. Hence, policies must address these risk factors. Policies intended to lessen the financial burden on families, such as including asthma care in national health insurance programs, are necessary due to the high morbidity from asthma. Establishing national guidelines that take into account local resources, socioeconomic circumstances, and risk factors is also critically important.16,21,22
Strengths and limitations
This study utilized GBD 2023 estimates to determine the prevalence of asthma and its premature mortality in the ESSA region. The estimates were disaggregated by sexes, age groups, locations, and years. Despite these, several limitations could be acknowledged. First, the availability and quality of the data in this region remain constrained. To solve this, establishing a robust vital event registration system and implementing a routine data collection and reporting process are necessary. Second, there might be potential inconsistency in case definitions and the risk of over- or under-diagnosis across countries. 23 Third, there was no specific “test” that directly measures the disease duration before death in the GBD 2023 estimation. Understanding the duration of asthma symptoms prior to a fatal attack is essential for identifying high-risk patients, improving clinical case management, and reducing preventable deaths. Studies indicate that asthma mortalities often fall into two distinct phenotypes called “rapid-onset” and “slow-onset,” which differ in pathology, triggers, and the speed of medical intervention needed. 24 Fourth, separate estimations were not available for Mauritius and Seychelles, which are located in Eastern Africa.
Conclusion
The prevalence of asthma in the region was comparable to the 2019 Global Burden of Disease estimates. From 1990 to 2023, prevalence and YLLs rates remained largely stable in both sexes and locations. Therefore, targeted interventions are needed to reduce asthma risk exposure among the population.
Footnotes
Acknowledgment
The authors thank the University of Washington Institute of Evaluation and Metrics for coordinating the GBD 2023 study.
Ethical considerations
This study used the GBD 2023 estimates, a secondary data source publicly available for international researchers. Moreover, the estimates were aggregated at population levels so that individuals’ identity was adequately anonymized. All methods were conducted in accordance with relevant guidelines and regulations for the use of secondary data in research. Therefore, ethical approval and informed consent were not needed for this study.
Author contributions
ST conceived and designed the study. ST, DCD, AB, HL, GND, DDH, and MTS were involved in the analysis and interpretation of the findings. All authors have approved the final version of the manuscript.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Data Availability Statement
We confirm that all data used in this study are derived from the GBD 2023 database, which is publicly available for research purposes.