Younger Americans die earlier and live in poorer health than their counterparts in other developed countries, with far higher rates of death from guns, car accidents and drug addiction, according to a new analysis of health and longevity in the United States.

Researchers have known for some time that the United States fares poorly in comparison with other rich countries, a trend established in the 1980s. But most studies have focused on older ages, when the majority of people die.

The findings were stark. Deaths before age 50 accounted for about two-thirds of the difference in life expectancy between males in the United States and their counterparts in 16 other developed countries, and about one-third of the difference for females. The countries in the analysis included Canada, Japan, Australia, France, Germany and Spain.

The 378-page study by a panel of experts convened by the Institute of Medicine and the National Research Council is the first to systematically compare death rates and health measures for people of all ages, including American youths. It went further than other studies in documenting the full range of causes of death, from diseases to accidents to violence. It was based on a broad review of mortality and health studies and statistics.