Life expectancies in high-income regions have been increased due to falling death rates from most cancers and cardiovascular diseases.
"The progress we are seeing against a variety of illnesses and injuries is good, even remarkable, but we can and must do even better," says lead author Dr. Christopher Murray, professor of Global Health at the University of Washington.
"However, this study shows that some major chronic diseases have been largely neglected but are rising in importance, particularly drug disorders, liver cirrhosis, diabetes and chronic kidney disease."
The analysis suggests that life expectancies in high-income regions have been increased due to falling death rates from most cancers - which are down by 15% - and cardiovascular diseases - which are down by 22%.
In low-income countries, rapidly declining death rates for diarrhea, lower respiratory tract infections and neonatal disorders have boosted life expectancy.
Despite the increases in global life expectancy by nearly 5.8 years in men and 6.6 years in women, some causes of death have seen increased rates of death since 1990.
These increased causes of death include:
- Liver cancer caused by hepatitis C (up by 125%)
- Atrial fibrillation and flutter (serious disorders of heart rhythm; up by 100%)
- Drug use disorders (up by 63%)
- Chronic kidney disease (up by 37%)
- Sickle cell disorders (up by 29%)
- Diabetes (up by 9%)
- Pancreatic cancer (up by 7%).
HIV/AIDS has 'erased years of life expectancy' in sub-Saharan Africa
The report also points to one notable global region where life expectancy is not increasing. Deaths from HIV/AIDS have erased more than 5 years of life expectancy in sub-Saharan Africa, say the authors. HIV/AIDS remains the greatest cause of premature death in 20 of the 48 sub-Saharan countries.
Since 1990, years of life worldwide lost due to HIV/AIDS is reported as having increased by 334%.
In Syria, war is the leading cause of premature death - the conflict caused an estimated 29,947 deaths in 2013, and up to 54,903 and 21,422 deaths in each of the preceding 2 years.
Countries that the authors consider to have made "exceptional gains in life expectancy" over the past 23 years include Nepal, Rwanda, Ethiopia, Niger, Maldives, Timor-Leste and Iran - where, for both sexes, life expectancy has increased by more than 12 years.
Life expectancy at birth in India increased from 57.3 years for men and 58.2 years for women in 1990 to 64.2 years and 68.5 years, respectively, in 2013. The authors say that India has made "remarkable progress" in reducing deaths, with the death rates for children dropping 1.3% per year for adults and 3.7% per year for children.
The report also welcomes dramatic drops in child deaths worldwide over the study period. In 1990, 7.6 million children aged 1-59 months died, but this death rate was down to 3.7 million by 2013.
Igor Rudan and Kit Yee Chan, from the Centre for Population Health Sciences and Global Health Academy at the University of Edinburgh Medical School in the UK, write in a linked comment:
"Estimates of the causes of the global burden of disease, disability, and death are important because they guide investment decisions that, in turn, save lives across the world.
Although WHO's team of experts have been doing fine technical work for many years, its monopoly in this field had removed incentives to invest more time and resources in continuous improvement [...] the competition between WHO and the GBD [Global Burden of Disease Study] has benefited the entire global health community, leading to converging estimates of the global causes of death that everyone can trust."