National mortality burden due to communicable, non-communicable, and other diseases in Ethiopia, 1990–2015: findings from the Global Burden of Disease Study 2015

GBD 2015 data were used to analyze the number of deaths and years of life lost (YLL) for Ethiopia. GBD 2015 utilizes comprehensive sources of data that meet inclusionary criteria and rigorous analysis to estimate trends of cause-specific mortality rates for 195 countries [16]. It identifies all available data sources, evaluates the quality, and corrects for known bias in each data source [7]. Data were adjusted for garbage coding and misclassification of causes of deaths. Garbage coding is the assignment of causes of death that are not the underlying cause of death [17]. The effect of garbage coding in the estimation of causes of death is usually high for countries that use vital registration and very low for countries using verbal autopsy. GBD 2015 used 171 site-years of cause of death data sources; these sources were used to produce national estimates for Ethiopia. Of the 171 site-year sources, 70 site-year were nationally representative and 52 site-year represented subnational locations in Ethiopia. Approximately 102 site-year data sources were from sibling history, an indirect method exploring maternal mortality through surviving siblings, and 63 site-years of data sources used verbal autopsy data collection techniques, the method of ascertaining cause of death from information obtained from relatives or associates of a deceased person [18]. Data were relatively scarce for Ethiopia; when this occurs, GBD uses two additional approaches to estimate causes of death. The first approach involves identifying covariates for each cause which are used to provide better estimates; the second borrows strength from the regional and super-regional model to produce estimates. The Supplementary Appendix provides further details on data sources [16].

The GBD approach to estimate all-cause mortality and cause-specific mortality rates has been previously described [16, 17]. Causes of death by age, sex, and year were measured mainly using cause of death ensemble modeling (CODEm) [7]. A detailed description of CODEm is reported elsewhere [17]. In brief, CODEm tests a wide range of models, such as mixed effects linear models and spatiotemporal Gaussian process regression (ST-GPR) models, and constructs an ensemble model based on the performance of the different models [17]. Out-of-sample predictive validity testing was used to select the ensemble model for estimation of morality rate [17]. In this model, uncertainty intervals are generated by sampling the posterior distribution of each component model in proportion to the weight of each model in the ensemble. Vital registration and VA data were corrected for garbage codes based on the GBD 2015 algorithm [17].

GBD 2015 used decomposition analysis to estimate mortality rates and causes of death for each age-sex-year group [9]. Trends were decomposed by the contribution of total increase in population size, aging of the population, and changes in age-specific and sex-specific rates [19, 20]. Two counterfactual sets of cause of death numbers were computed: a population growth scenario was computed as the number of deaths expected in 2015 if only total population numbers increased to the level of 2015 but the age-sex structure of population remained the same as in 1990 and age-sex specific rates remained at 1990 levels; and, two, a population growth and population aging scenario was computed as the number of deaths expected in 2015, using 1990 age-sex specific rates and 2015 age-specific and sex-specific population numbers [20]. Accordingly, three different scenarios are presented as a percentage change compared to 1990. The difference between 1990 numbers and the population growth scenario is the change in death numbers strictly due to growth in the total population. The change from the population growth scenario to the population growth and aging scenario is the number of deaths due to aging of the population. The difference between 2015 deaths, population growth, and aging scenario is the difference in deaths due to epidemiological change in age-specific and sex-specific death rates [7, 20]. While estimating crude death rates, the effect of national population growth during the study period was controlled, and changes in population size and composition were controlled while estimating age-standardized rates [21].

We followed GBD categorization of diseases and injuries to present and interpret the estimates. GBD uses a hierarchy of mutually exclusive and collectively exhaustive causes that organizes 249 fatal diseases and injuries into four levels [16]. The first level shows three broad categories: communicable, maternal, neonatal, and nutritional (CMNN) disorders, non-communicable diseases (NCDs), and injuries. Level 2 has 21 cause groups, such as cardiovascular diseases, whereas Levels 3 and 4 provide more disaggregated causes [21].We present the estimates in terms of crude death rates, crude YLL rates, age-standardized death rates, and age-standardized YLL rates, with 95% uncertainty intervals (UI). Years of life lost for each cause were estimated by using standard GBD 2015 methodology [7, 17]. This method involves multiplying deaths occurring as a result of a given cause by the reference standard life expectancy at the age when the death occurred, based upon the lowest observed death rate for each 5-year age group for populations greater than 5 million [22]. GBD 2015 produced uncertainty intervals at key steps of all-cause and cause-specific mortality estimation to account for uncertainties that arise from adjusting sources, sample size, and other model specifications [17]. We report positive percentage changes to show increasing trends and negative percentage changes to show decreasing trends of rates from 1990 to 2015.

Overall, 677,045.6 (95% UI: 502,236.1–908,743.0) deaths occurred in Ethiopia in 2015 and 316,969.7 (95% UI: 205,647.4–496,323.5) of these were among females. Crude death rates for broad groups of causes and the crude all-cause mortality rate are presented in Table 1. The crude all-cause mortality rate was 680.9 per 100,000 people (95% UI: 505.1–913.9) in 2015, of which 337 (95% UI: 273.8–421.3) per 100,000 were caused by CMNN diseases and 286.9 (95% UI: 188.1–423.0) per 100,000 were due to NCDs. Overall, the death rate has decreased for the three broad groups of causes from 1990 to 2015; however, CMNN diseases and injuries showed greater reduction of 75% each, while NCDs showed a slower decline of 40% (Table 1).

In 2015, HIV/AIDS and tuberculosis collectively caused 72.8 (95% UI: 50.9–101.0) deaths per 100,000 people (Table 1). Diarrhea, lower respiratory infections, and other common infectious diseases caused 147.4 (95% UI: 113.9–191.0) deaths per 100,000 people. Cardiovascular diseases and neoplasms caused 120.5 (95% UI: 77.1–177.5) and 55.6 (95% UI: 32.8–89.8) deaths per 100,000 people, respectively (Table 1). Transport injuries and unintentional injuries caused 14.2 (95% UI: 9.0–22.4) and 29.0 (95% UI: 19.8–41.9) deaths per 100,000 people, respectively.

All Level 2 cause categories declined from 1990 to 2015, with a major reduction in CMNN-related causes of death (Table 1). The top two leading causes of death that showed decline were HIV/AIDS with tuberculosis, which decreased by 52%, and diarrhea, lower respiratory infections, and other common infectious diseases, which collectively declined by 79%. The two leading causes among NCDs, cardiovascular diseases and neoplasms, declined by 39 and 29%, respectively. Furthermore, mortality due to unintentional and transport injuries fell 61 and 52%, respectively, between 1990 and 2015.

The burden from CMNN diseases, NCDs, and injuries, in terms of age-standardized death rates for both sexes and all age groups, is shown in Table 2. Overall, total mortality and age-standardized death rates for each of the broad groups of causes decreased between 1990 and 2015. In 2015, the all-cause age-standardized death rate was 1248.0 per 100,000 people (95% UI: 860.3–1760.3), of which NCDs caused 710.9 (95% UI: 468.8–1036.2) and CMNN diseases caused 445.0 (95% UI: 326.7–600.7) deaths per 100,000 people (Table 2). NCDs showed a smaller reduction of 37% between 1990 and 2015 compared to the 65% decrease for CMNN causes and 70% for injuries (Table 2). Non-communicable diseases were the leading causes of age-standardized death rates, causing 711 deaths per 100,000 people (95% UI: 468.8–1036.2) in 2015, as indicated in Fig. 1.

Diarrhea, lower respiratory infections, and other common infectious diseases caused 223.6 (95% UI: 158.0–308.8) age-standardized deaths per 100,000 people in 2015, combined. The age-standardized death rate for HIV/AIDS and tuberculosis, combined, was 122.0 (95% UI: 79.9–174.8) deaths per 100,000 people (Table 2). Cardiovascular diseases and neoplasms caused 350.0 (95% UI: 232.7–500.7) and 122.5 (95% UI: 74.3–192.4) deaths per 100,000 people, respectively (Table 2). Transport injuries and unintentional injuries caused 21.4 (95% UI: 13.4–34.5) and 50.1 (95% UI: 32.6–73.4) deaths per 100,000 people, respectively.

From 1990 to 2015, all Level 2 cause categories declined, with a major reduction of CMNN causes of death (Table 2). The combined age-standardized death rate from HIV/AIDS and tuberculosis declined by 54%. Similarly, the death rate from diarrhea, lower respiratory infections, and other common infectious diseases collectively declined 67% (Table 2). The age-standardized death rates from cardiovascular diseases and neoplasms showed 37 and 31% reductions, respectively, between 1990 and 2015. Age-standardized death rates due to injuries also declined, as the rate for unintentional injuries declined by 53% and that for transport injuries by 48% (Table 2).

As shown in Fig. 2, the top 10 leading causes accounted for more than 50% of the total age-standardized death rate in 2015. Six of the 10 leading causes were NCDs; however, only two NCDs were in the top five leading causes. The top five leading causes in 2015 were ischemic heart disease, lower respiratory infections, diarrheal diseases, tuberculosis, and hemorrhagic stroke and caused 141.9 (95% UI: 92.3–208.0), 98.7 (95% UI: 67.5–139.8), 88.6 (95% UI: 59.4–127.1), 86.3 (95% UI: 47.0–138.6), and 62.7 (95% UI: 37.9–94.9) deaths per 100,000 people, respectively (Fig. 2 and Table 2).

The percent change in the age-standardized death rate per 100,000 for the top 30 leading causes of death between 1990 and 2015 is shown in Fig. 3. Significantly large reductions occurred in three of the top five leading causes of death: diarrheal disease (69%), tuberculosis (64%), and lower respiratory infections (56%) (Fig. 4). The first, fifth, and sixth leading causes of death also declined: ischemic heart disease (29%), hemorrhagic stroke (46%), and ischemic stroke (33%) (Fig. 4). Between 1990 and 2005, HIV/AIDS increased by 1013%; however, since 2005 this rate has decreased by 70% (data not shown).

Other causes that declined by 50% or greater are shown in Fig. 3 and include neonatal encephalopathy, iron-deficiency anemia, protein-energy malnutrition, and preterm birth complications.

In 2015, the all-cause crude YLL rate was 32,397.0 per 100,000 people (95% UI: 26,283.3–40,426.8), of which CMNN diseases caused 20,744.6 (95% UI: 17,785.6–24,205.2) and NCDs caused 8823.0 (95% UI: 5926.8–12,768.2) per 100,000 people (Table 3). The crude YLLs per 100,000 people showed higher reductions for CMNN diseases and injuries – 77 and 79%, respectively – while NCDs declined 47% (Table 3).

All Level 2 causes showed reductions in crude YLL rates. CMNN diseases declined between 51 and 94% (Table 3). The two leading causes of NCD-related YLL rates decreased as well. Cardiovascular diseases decreased by 50% and neoplasms by 30%. The leading causes due to injuries also decreased. Unintentional injury declined by 67% and transport injury by 55% (Table 3).

In 2015, the all-cause age-standardized YLL rate was 35,803.9 (95% UI: 26,058.9–49,095.4), of which CMNN diseases caused 17,950.6 (95% UI: 14,377.9–22,768.8) and NCDs caused 14,761.9 (95% UI: 9422.7–22,306.4) YLLs per 100,000 people (Table 4). The age-standardized YLL percentage contribution of CMNN diseases was 60% in 1990 and 51% in 2015, whereas NCDs contributed 27% in 1990 and 41% in 2015 (Fig. 4). The age-standardized YLL rates declined by 69% for CMNN, 76% for injuries, and 44% for NCDs. CMNN diseases were the leading causes of age-standardized YLL rates in 2015, as indicated in Fig. 4.

The top 10 leading causes accounted for 45% of the total age-standardized YLL rate in 2015 (Fig. 5). Seven of the 10 leading causes were CMNN diseases. The top five leading causes were lower respiratory infections, diarrheal diseases, tuberculosis, ischemic heart disease, and HIV/AIDS, causing 2987.2 (95% UI: 2165.5–4017.9), 2502.3 (95% UI: 1410.4–4151.9), 2405.2 (95% UI: 1676.8–3309.1), 2380.3 (95% UI: 1446.5–3680.0), and 1236.9 (95% UI: 861.1–1623.3) per 100,000 people (Fig. 5 and Table 4).

The combined HIV/AIDS and tuberculosis age-standardized YLL rate declined 53%, while diarrhea, lower respiratory infections, and other common infectious diseases declined 75%, collectively. The two leading causes of NCDs, cardiovascular diseases and neoplasms, declined by 46 and 32%, respectively. Leading causes of injuries also declined, unintentional injury by 60% and transport injury by 52% (Table 4).

The five leading causes of age-standardized YLL rates for Ethiopia generally showed greater declines when compared to the Eastern sub-Saharan Africa sub-region and the sub-Saharan Africa region; however, ischemic heart disease did not follow this pattern, as indicated in Fig. 6. The contribution of diseases to the total age-standardized death rate and the YLL rate per 100,000 in Eastern sub-Saharan African countries showed variation, as indicated in Figs. 7 and 8.

Primarily, the findings are useful to highlight the performance of the previous health sector development plan for Ethiopia and to create benchmarks for the health sector transformation plan [12]. These findings are also helpful for revisiting some of the strategies and budget reallocations in order to incorporate more data on health and the demographic and epidemiological transitions happening throughout the country. However, findings with wider 95% UIs need to be cautiously considered during policy debates and priority-setting. For example, the uncertainty intervals for age-standardized death rates caused by non-communicable disease were 14,761.9 (95% UI: 9422.7–22,306.4) and for CMNN diseases, 17,950.6 (95% UI: 14,377.9–22,768.8); this shows lack of adequate and quality data due to the wide interval. With regard to the leading causes of age-standardized premature mortality rates, HIV/AIDS has relatively narrow uncertainty intervals, whereas lower respiratory infections, tuberculosis, diarrheal diseases, and ischemic heart disease have shown relatively wider uncertainty intervals. The health burden variation between urban and rural populations and between regional states and districts requires further exploration to support public health policy at each level.

There was significant progress in reducing premature mortality and death from lower respiratory infections, diarrheal diseases, tuberculosis, and HIV/AIDS in Ethiopia for the past two and a half decades; however these diseases are still large drivers of premature mortality and death. Vaccine-preventable diseases such as measles, whooping cough (pertussis), and tetanus have largely decreased, showing the effectiveness of the health care system and vaccination campaigns. This was instrumental in reducing child mortality in Ethiopia [2]. However, the findings may vary with subnational regional states and/or urban/rural populations which GBD 2015 did not capture. This provides one possible direction for future collaborations with the nine autonomous regional states and two city administration councils in Ethiopia.

The different types of cardiovascular diseases, such as ischemic heart disease, hemorrhagic stroke, ischemic stroke, and hypertensive heart disease, were leading causes of premature mortality and age-standardized death rates in Ethiopia. Cervical cancer, diabetes, chronic respiratory diseases, and asthma were also among the leading causes of death and premature mortality rates. These causes are all recent phenomena among Ethiopians; these findings can assist in designing new public health strategies and reinforce recently developed strategies and interventions on cardiovascular disease, cancer, diabetes, and chronic respiratory diseases [13].

Our findings could reinforce the implementation of cost-effective strategies, improve resource allocation, and strengthen partnership and community engagement around cardiovascular disease, diabetes, and cancer prevention and control in Ethiopia [40]. In recent years, the MOH and its partners have developed national strategies and action plans focusing on cardiovascular disease, cancer, diabetes, chronic respiratory diseases, and mental health; however, there are implementation challenges. These challenges include, but are not limited to, human resource capacity, financial resources, and the lack of local and global advocacy. There is also a need to reinforce efforts and initiatives on cervical cancer screening, hypertension screening, diabetes screening, HBV vaccination, and media advocacy regarding leading causes of premature mortality and deaths for Ethiopia [12].

Health services that target cardiovascular diseases, cancers, chronic respiratory diseases, and diabetes need to be integrated within the existing primary health care system. Furthermore, these services need to extend to the health post, health extension program, and secondary and tertiary health facilities [2]. Establishing centers and a proper referral system would be helpful, such as oncology centers, cardiac centers, and mental health centers in the secondary and tertiary hospitals. Additionally, there is a need to involve the private sector and civic society in delivering health services for cardiovascular disease, cancer, diabetes, and their risk factors. Moreover, human resource capacity development both in the pre-service and in-service sectors need to consider addressing the double burden of common infectious diseases such as lower respiratory infections, diarrheal diseases, tuberculosis, and non-communicable diseases like cardiovascular disease, cancer, diabetes, and their risk factors. To succeed, essential medical technologies and treatment for cardiovascular disease, cancer, and diabetes are needed to strengthen the health system.

Ethiopia has already ratified the WHO Framework Convention on Tobacco Control (FCTC) and the Protocol to Eliminate Illicit Trade in Tobacco in 2015 [41]; however, it is important to develop implementation guidelines and regulatory mechanisms that can enforce the convention in order to reduce the population’s risk of developing cardiovascular disease, cancer, diabetes, and chronic respiratory diseases. Reducing tobacco use by establishing tobacco-free environments, increasing public knowledge of the hazards of tobacco, and continuously increasing taxes on purchase and sales of tobacco products are recommended interventions in the convention. There is also a need to develop and implement guidelines on alcohol use in Ethiopia as excessive alcohol use is widely prevalent in Ethiopia [15, 42].

The impact of the different types of cardiovascular disease, cancers, chronic respiratory disease, asthma, and diabetes, as well as their risk factors, could affect sectors beyond the health sector. Therefore, the response for the prevention and control of these leading non-communicable diseases require a multi-sectoral approach. Multi-sectoral strategies have been widely practiced to respond to the HIV/AIDS epidemic in Ethiopia. This expertise would be useful in combating non-communicable diseases such as cardiovascular disease, cancer, diabetes, and their risk factors in Ethiopia. This strategy should involve a variety of sectors such as health, agriculture, trade and industry, education, urban planning, and transportation. These sectors can be coordinated to prevent and control the specified diseases based upon their shared risk factors including tobacco, physical inactivity, unhealthy diet, and excessive alcohol use, as well as “Khat” consumption [42]. Therefore, a collective multi-sectoral response and integration with the existing health care system will allow for the mobilization of resources, foster strong political commitment, and foster a strong collaboration with NCD stakeholders, ultimately addressing the burden of cardiovascular disease, cancer, diabetes, and chronic respiratory disease in Ethiopia. Initiatives on cardiovascular diseases, cancer, diabetes, and chronic respiratory diseases need to adapt some relevant and successful strategies from CMNN initiatives such as HIV/AIDS, tuberculosis, and diarrheal disease to design cost-effective packages.

The 95% UI for premature death and death rate estimates varies by causes that positively or negatively affect health policy debates and decisions for Ethiopia. Although attaining good-quality vital statistics could be a long-term goal for Ethiopia, an interim solution must be devised. Investing in developing a national data management center and developing a national data-sharing policy and culture that would pool all data sources available in the country would help to provide more accurate burden of disease estimates. This would ultimately better inform policy debates and decisions at national and subnational levels in Ethiopia. Survey and surveillance data and reports need to be released in a timely manner in order to maximize their use and relevance. Moreover, investing in national verbal autopsy studies, such as post-census and/or post-demographic health surveys, would expand health demographic surveillance sites to new locations and would help to fill cause of death data gaps in Ethiopia. Verbal autopsy studies need to capture the different agro-ecological and population structure of the country. Finally, Ethiopia requires higher investment and commitment to generate quality cause of death data through Vital Events Registration Agency (VERA), which was established in August 2016 [43], strengthening and tailoring surveillance systems and surveys toward the inclusion of non-communicable diseases and their risk factors in Ethiopia.