Global mortality due to rheumatic heart disease fell by about 48% during a recent 25-year-period, but some of the poorest areas of the world were left behind, according to a report in the New England Journal of Medicine.

Those regions included Oceania, South Asia, and central sub-Saharan Africa, where rheumatic heart disease remains endemic, wrote David A. Watkins, MD, MPH, of the University of Washington, Seattle, and his coinvestigators. “We estimate that 10 persons per 1,000 population living in South Asia and central sub-Saharan Africa and 15 persons per 1,000 population in Oceania were living with rheumatic heart disease in the year 2015,” they wrote. “Improvements in the measurement of the burden of rheumatic heart disease will assist in planning for its control and will help identify countries where further investments are needed.”

Rheumatic heart disease is a sequela of untreated streptococcal pharyngitis, which is associated with poverty, overcrowding, poor sanitation, and other social predictors of poor health. In high-income countries, treatment with penicillin G and improved sanitation had nearly eliminated rheumatic heart disease by the late 20th century, but local studies pointed to ongoing morbidity and mortality in lower-income regions.

To better define the problem, Dr. Watkins and his associates analyzed epidemiologic studies of rheumatic heart disease from 1990 through 2015. They used the Cause of Death Ensemble model , which estimates mortality more reliably than older methods, and DisMod-MR (version 2.1) , which sums epidemiologic data from multiple sources and corrects for gaps and inconsistencies ( N Engl J Med. 2017;377:713-22 ).

Worldwide, about 319,400 individuals died of rheumatic heart disease in 2015, the researchers reported. Age-adjusted death rates fell by about 48% (95% confidence interval, 45%-51%), from 9.2 deaths per 100,000 population in 1990 to 4.8 deaths per 100,000 population in 2015. But this global trend masked striking regional disparities. In 1990, 77% of deaths from rheumatic heart disease occurred in endemic areas of Africa, South Asia, Oceania, and the Caribbean; by 2015, 82% of deaths occurred in endemic regions. Oceania, South Asia, and central sub-Saharan Africa had the highest death rates and were the only regions where the 95% confidence intervals for 1990 and 2015 overlapped, the investigators noted.

In 2015, age-standardized death rates exceeded 10 deaths per 100,000 population in the Solomon Islands, Pakistan, Papua New Guinea, Kiribati, Vanuatu, Fiji, India, Federated States of Micronesia, Marshall Islands, Central African Republic, and Lesotho, they reported. Estimated fatalities were highest in India (119,100 deaths), China (72,600), and Pakistan (18,900). They estimated that in 2015, there were 33.2 million cases of rheumatic heart disease and 10.5 million associated disability-adjusted life-years globally.

The study excluded “borderline” or subclinical rheumatic heart disease, which is detected by echocardiography and whose management remains unclear. “Better data for low-income and middle-income countries are needed to guide policies for the control of rheumatic heart disease,” the investigators wrote. They recommended studying death certificate misclassifications, disease prevalence among adults, and longitudinal trends in nonfatal outcomes and excess mortality.

Funders of the study included the Bill and Melinda Gates Foundation and the Medtronic Foundation. Dr. Watkins disclosed grants from the Medtronic Foundation during the conduct of the study and grants from the Bill and Melinda Gates Foundation outside the submitted work.