Background
The Global Burden of Diseases, Injuries, and Risk Factors Study 2015 (GBD 2015) provides an up-to-date analysis of the burden of diarrheal diseases. This study assesses cases, deaths, and etiologies spanning the past 25 years and informs the changing picture of diarrheal disease worldwide.
Methods
We estimated diarrheal mortality by age, sex, geography, and year using the Cause of Death Ensemble model (CODEm), a modeling platform shared across most causes of death in the GBD 2015 study. We modeled diarrheal morbidity, including incidence and prevalence, using a meta-regression platform called DisMod-MR. We estimated etiologies for diarrheal diseases using a counterfactual approach that incorporates the etiology-specific risk of diarrheal disease and the prevalence of the etiology in diarrhea episodes. We used the Socio-demographic Index, a summary indicator derived from measures of income per capita, educational attainment, and fertility, to assess trends in diarrheal mortality. The two leading risk factors for diarrhea – childhood malnutrition and unsafe water, sanitation, and hygiene – were used in a decomposition analysis to establish the relative contribution of changes in diarrhea disability-adjusted life years (DALYs).
Findings
Globally, in 2015, we estimate that diarrhea was a leading cause of death among all ages (1.31 million deaths, 95% uncertainty interval [95% UI] 1.23 million to 1.39 million), as well as a leading cause of DALYs because of its disproportionate impact on young children (71.59 million DALYs, 66.44 million to 77.21 million). Diarrhea was a common cause of death among children under 5 years old (499,000 deaths, 95% UI 447,000–558,000). The number of deaths due to diarrhea decreased by an estimated 20.8% (95% UI 15.4–26.1) from 2005 to 2015. Rotavirus was the leading cause of diarrhea deaths (199,000, 95% UI 165,000–241,000), followed by Shigella (164,300, 85,000–278,700) and Salmonella (90,300, 95% UI 34,100–183,100). Among children under 5 years old, the three etiologies responsible for the most deaths were rotavirus, Cryptosporidium, and Shigella. Improvements in safe water and sanitation have decreased diarrheal DALYs by 13.4%, and reductions in childhood undernutrition have decreased diarrheal DALYs by 10.0% between 2005 and 2015.
Interpretation
At the global level, deaths due to diarrheal diseases have decreased substantially in the past 25 years, although progress has been faster in some countries than others. Diarrhea remains a largely preventable disease and cause of death, and continued efforts to improve access to safe water, sanitation, and childhood nutrition will be important in reducing the global burden of diarrhea.