Global look at sex differences in young people’s mortality

Males and females have different death rates due to a complex variety of biological, genetic and social factors. The sex differentials in mortality have been well documented for children younger than 5 years, but until now have not been systematically examined from the age of 5 to 24. Researchers at KAUST, along with colleagues in Belgium and the U.S., have addressed this knowledge gap with a detailed study of sex-specific mortality worldwide between 1990 and 2021.^[1]

“Although our work did not focus on possible reasons behind sex differences in mortality across countries, our results should help researchers who are experts in specific countries to investigate the possible causes and any issues needing to be addressed,” says KAUST biostatistician and study leader Fengqing Chao. “Our study is the first step in trying to find ways to reduce preventable deaths for people aged under 25.”

The researchers assembled their data from a combination of death registration systems and full birth and sibling histories from surveys and reports on household deaths in censuses. They used innovative analytical software developed by KAUST professor Håvard Rue.

The study’s findings are presented as mortality sex ratios. For example, in 2021 on a global scale, males from the age of 0 to 4 years were 13 percent more likely to die than females, represented by the ratio 1.13. The ratio increased to 1.16 for the 5-to-14-year-old age group, then reached 1.65 for ages 15 to 24.

The work also revealed that the global sex-linked difference in mortality increased between 1990 and 2021, driven by faster declines in female mortality than for males. In 2021 the probability of a newborn male reaching an age of 25 years was 94.1 percent, compared to 95.1 percent for a female.

The study’s key detailed findings show that in some countries the figures deviated significantly in comparison with countries that have similar mortality rates, while still showing males were more likely to die than females. In India, Iran, Egypt, Bangladesh and Algeria, females aged 0-4 years were more likely to die than those in other countries with a similar total mortality. Females aged 5 to 14 were also disadvantaged in Suriname and in a total of 13 countries for ages 15 to 24: Afghanistan, Eswatini, Uzbekistan, Bangladesh, Suriname, Papua New Guinea, Turkmenistan, India, Nepal, Fiji, Tajikistan, Kyrgyzstan and Algeria.

Increased male mortality relative to countries with similar total mortality was found in Vietnam for ages 0 to 4 and in eight countries for ages 15 to 24: Venezuela , El Salvador, Brazil, Colombia, Thailand, Trinidad and Tobago, Uruguay and Mexico.

“Our study is part of our collaboration with UNICEF and was included as part of its annual report on child mortality, helping to inform policymakers on resource allocation,” says KAUST Biostatistics research group leader Hernando Ombao. “We will continue my collaboration with UNICEF and other UN agencies on monitoring other disparities in mortality, such as between urban and rural residents.”