(Reuters) - Medical progress and global efforts to reduce infant and child mortality have reversed historical trends and mean that death rates among adolescents are now higher than in children, researchers said on Tuesday.
Looking at data from 50 countries over the second half of the 20th century, the study found the majority of deaths in young people was through incidents such as car accidents or reckless behavior -- and that violence and suicide have also become key causes of death in this group.
The findings, published in the Lancet medical journal, partly reflect success in reducing death rates among very young children, the researchers said.
But the strong international focus on reducing infant and child mortality has not been matched by a similar efforts in older groups, they said, even though more than two-fifths of the world's population is in the five to 24 years age group.
"These trends are likely to continue because mortality in children younger than five years is expected to decline further, and injury-related mortality is expected to increase in the next 25 years," said Russell Viner from the University College London institute of child health, who led the study.
Commenting on the findings, Michael Resnick of the University of Minnesota in the United States, who was not involved in the study, said they showed how "the profound health and social changes that have accompanied economic development and urbanization are particularly toxic for young people in both high-income and low-income settings."
A study in 2009 by World Health Organization (WHO)-supported researchers found that 40 percent of adolescent deaths were due to injuries and violence.
Against this background, Resnick said breakthroughs in medical progress and service delivery were not enough to counter health threats faced by young people because of the major role played by factors such as socioeconomic conditions, opportunity and access to education.
Viner's team used the WHO mortality database to analyze data for 50 rich and poor nations between 1955 and 2004. They looked at patterns of mortality by age group, sex and cause of death -- divided into infectious diseases, chronic diseases and injury.
To find changes in mortality, they calculated death rates averaged over three five-year periods -- 1955 to 1959, 1978 to 1982, and 2000 to 2004.
Findings showed that in the 1950s, mortality in the one to four age group far exceeded that of all other age groups in all regions studied. But in the 50 years up to 2004, death rates in children aged one to nine fell by 80 to 93 percent, mostly due to reductions in deaths from infectious disease.
In contrast, declines in death rates in those aged 15 to 24 years were only about half that in children, largely because of increases in injury-related deaths, particularly in young men.
The researchers found that by the start of the 21st century, injuries -- such as in incidents like car crashes and street or gang violence -- were responsible for 70 to 75 percent of all deaths in young men aged 10 to 24 in all the regions studied.
By 2004, suicide and violence were responsible for between a quarter and a third of deaths in young men aged 10 to 24 years, and death rates in young men aged 15 to 24 are now two to three times higher than in boys aged one to four, they said.
(Editing by Alison Williams)