Population growth, population ageing and changes in disease patterns have reshaped global health priorities over the past three decades. An international research team assessed how mortality and disability-adjusted life-year burdens changed across major disease categories from 1990 to 2021, how these burdens were distributed across different levels of socioeconomic development, and which demographic and epidemiological factors contributed to changes in total DALYs.
The researchers analysed estimates from the Global Burden of Disease Study 2021 for 204 countries and territories. A disability-adjusted life year, or DALY, represents one year of healthy life lost because of premature death or disability. Joinpoint regression was used to assess long-term trends. Countries and territories were also ranked according to the sociodemographic index, or SDI, which reflects income, education and fertility. The population-weighted slope index of inequality and relative concentration index were used descriptively to summarise the absolute and relative gradients in disease burden across the SDI distribution. Decomposition analysis separated changes in total DALYs into contributions from population growth, population ageing and epidemiological change.
Cardiovascular diseases had the highest mortality and DALY rates among the major disease categories in 2021. From 1990 to 2021, neurological disorders showed the largest increase in mortality rates, with an average annual increase of 2.0%. Diabetes and kidney diseases showed the largest increase in DALY rates, with an average annual increase of 1.8%. These findings highlight the growing importance of neurological and metabolic diseases in global health.
The study also identified contrasting patterns across the SDI distribution based on analyses of all-age crude mortality and DALY rates. Mortality and DALY burdens from communicable, maternal, neonatal and nutritional diseases remained concentrated towards the lower-SDI end, but their absolute and relative gradients were weaker in 2021 than in 1990. In contrast, non-communicable disease-related mortality and DALY burdens remained concentrated towards the higher-SDI end, and their absolute and relative gradients were stronger in 2021 than in 1990. The researchers emphasised that these results were based on all-age crude mortality and DALY rates. The patterns therefore reflect the disease burden observed under existing population structures, including differences in population age composition. The concentration of non-communicable disease burden towards the higher-SDI end should not be interpreted as evidence that lower-SDI settings have lower underlying risks of non-communicable diseases. The results are also distinct from analyses based on age-standardised rates.
Between 1990 and 2021, the global number of non-communicable disease-related DALYs increased by 577.0 million. Population growth contributed an estimated increase of 560.1 million DALYs, while population ageing contributed an increase of 340.2 million. These increases were partly offset by favourable epidemiological change, which reflects improvements in age-specific DALY rates. The contributions should therefore be interpreted together because the different components operated in opposite directions. Population growth played a more prominent role in lower-SDI groups, whereas population ageing was more prominent in higher-SDI groups.
The findings support a dual approach to global health. Lower-SDI settings require continued investment in infectious disease prevention, maternal and neonatal health services and nutritional improvement, while also preparing for a growing burden of non-communicable diseases. Across all development levels, prevention, early diagnosis and long-term management of cardiovascular diseases, neurological disorders, diabetes and kidney diseases will become increasingly important as populations grow and age.
The study relied on modelled GBD estimates, and the availability and quality of underlying data varied across countries and territories. The SDI-related measures were descriptive, and the decomposition analysis should not be interpreted as establishing causal relationships. The international research team included investigators from Xi’an Jiaotong University, Monash University, the University of Melbourne, Western Sydney University and Alfred Health.
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