Worldwide, mortality in adolescents and young adults has overtaken that in children aged 1-4 years, except for a few very-low-income countries, according to a report published online March 29 in the Lancet.

In particular, mortality among young men aged 15-24 years is now two to three times higher than that in young boys, said Russell M. Viner, Ph.D., of the University College London Institute of Child Health and his associates.

This represents a reversal of the historical mortality pattern, and is driven largely by two trends: decreases in both communicable and noncommunicable childhood diseases, and an upsurge in violence- and injury-related deaths in young men. For the first time, children aged 1-4 years now have lower mortality than young men and equivalent mortality to young women, the investigators said.

Mortality among women aged 15-24 years has always been relatively high and continues to be so, because of the excess mortality related to pregnancy and childbirth in this age group.

Research concerning mortality in later childhood, adolescence, and young adulthood has been "neglected," compared with research in infancy and later adulthood, in part because of "the assumption that this period is the healthiest time of life," Dr. Viner and his colleagues said. "However, during the past 50 years, global social, economic, and political changes have adversely affected patterns of health and disease in adolescents and young adults."

The investigators analyzed information in the World Health Organization’s mortality database in what they described as the first international study to examine trends in cause-specific mortality in people aged 1-24 years residing in 50 high-, middle-, low-, and very-low-income countries between 1955 and 2004.

Importantly, because of inaccurate or incomplete data during this period, some very-low-income countries in Africa and Asia could not be included in the study, nor could India and China, the two countries with the largest populations of adolescents and young adults. The study findings therefore cannot be generalized to these countries, the researchers noted.

The study population comprised 436 million young people, representing 15% of the global population in this age group.

In the 1950s, mortality at ages 1-4 years greatly exceeded that of all other age groups in all regions studied. But during the ensuing 50 years, mortality among children aged 1-9 years declined by a dramatic 80%-93%, largely because of a steep decrease in communicable diseases – a decline that was as high as 50-fold in some areas.

Mortality related to noncommunicable juvenile diseases such as asthma, diabetes, and cardiovascular disorders also declined.

Yearly decreases in mortality were large, at approximately 2%, among children aged 5-14 years. In contrast, yearly decreases were much lower, at approximately 0.8%, in males aged 15-24 years. Yearly decreases among young women were intermediate between these two extremes, at approximately 1.5%.

Trends in injury-related deaths also differed greatly between children on the one hand and adolescents combined with young adults on the other. In 2004, injury-related mortality accounted for 25%-36% of all childhood mortality, but for 70%-75% of mortality among males aged 15-24 years. In children, fatal injuries were usually related to transportation, while in adolescents and young men they were often related to violence, increased sensation-seeking behavior, and suicide.

Violence – both interpersonal assault and violence due to larger political upheavals – and suicide became increasingly important causes of death among young men all over the world and among young women in certain regions such as eastern Europe. Overall, violence and suicide now account for up to one-third of mortality in adolescents and young adults in all regions.

"These trends are likely to continue because mortality in children younger than 5 years is expected to decline further, [while] injury-related mortality is expected to increase ... with the continuation of the epidemiological transition in developing countries," according to Dr. Viner and his associates (Lancet 2011 March 29 [doi:10.1016/S0140-6736(11)60106-2]).

Undoubtedly, the inclusion of certain "hot spots" in this study fueled these trends. Eastern European countries showed a clear peak in mortality in the aftermath of the fall of communism, as did some Central and South American countries enmeshed in civil wars.

Pregnancy and childbirth were important causes of mortality in adolescent and young women across the globe in the 1950s, but remain so only in the many low-income countries, and some middle-income countries, today. Such mortality is negligible, accounting for less than 1% of total mortality, in higher-income countries, but it accounts for some 6% of mortality in Central and South American countries.

The study results "support the need for a new focus on the health of adolescents and young adults worldwide. Future global health targets should include the causes of death in people aged 10-24 years, and should extend beyond HIV infection and maternal mortality to include injury and mental health," the investigators said.

There was no funding source for this study. Dr. Viner reported consulting for Esai, and an associate reported receiving travel and living expenses from the World Health Organization.

Mortality at Ages 15-24 Overtakes Mortality at Ages 1-4 Worldwide