(CNN) As the world's population continues to rise, more children are surviving into adulthood, a new study finds, but rates of disability have increased as well.

Research published Monday in the journal JAMA Pediatrics found that from 1990 to 2017, global child and adolescent deaths decreased 51.7%, while disability increased 4.7%. Additionally, there is a growing gap between young people's health outcomes between different countries.

The study was part of the Global Burden of Disease report. In 2017, the most common killers of children and adolescents were diarrhea, acute malnutrition and lower respiratory tract infections. However, deaths among children and adolescents fell from 13.77 million in 1990 to 6.64 million in 2017.

Among countries with higher socioeconomic development, some of the main contributors to disability were birth defects, neonatal disorders, headache, dermatitis and anxiety. In lower-development countries, lower respiratory infections, diarrhea and malaria, as well as birth defects and neonatal disorders contributed to disability.

When researchers looked at death and disability in people up to age 19 in 195 territories and countries, they found that the regions with the greatest decline in childhood deaths were Central, Eastern and sub-Saharan Africa, while the fastest rates of decreased death were in Andean Latin America, South Asia and East Asia. The authors attribute these improvements to practices such as more widespread vaccinations, improved sanitation and nutrition, and targeting of malaria and sexually transmitted infections.

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