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, said a new analysis of health and longevity in the United States.

Researchers have known that the nation fares poorly in comparison with other rich countries, a trend established in the 1980s. But most studies have focused on older ages, when most people die.

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

The 378-page study by 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 U.S. youths.

The panel called the pattern of higher rates of disease and shorter lives "the U.S. health disadvantage," and said it was responsible for dragging the nation to the bottom in terms of life expectancy over the past 30 years. U.S. men ranked last in life expectancy among the 17 countries in the study, and U.S. women ranked second-to-last. Even the people most likely to be healthy, like college-educated Americans and those with high incomes, fare worse on many health indicators.

"Something fundamental is going wrong," said Dr. Steven Woolf, chair of the Department of Family Medicine at Virginia Commonwealth University, who headed the panel. "This is not the product of a particular administration or political party. Something at the core is causing the U.S. to slip behind these other high-income countries. And it's getting worse."

Car accidents, gun violence and drug overdoses were major contributors to years of life lost by Americans before age 50. The rate of firearm homicides was 20 times higher in the United States than in the other countries, said the report, which cited a 2011 study of 23 countries. And though U.S. suicide rates were lower, firearm suicide rates were six times higher.

Sixty-nine percent of all U.S. homicide deaths in 2007 involved firearms, compared with an average of 26 percent in other nations, the study said.

Panelists were surprised at how consistently Americans ranked at the bottom. The United States had the second-highest death rate from the most common form of heart disease, and the second-highest death rate from lung disease. The nation also has the highest infant mortality rate among these countries, and its young people have the highest rates of sexually transmitted diseases, teen pregnancy and deaths from car crashes. Americans also had the lowest probability overall of surviving to 50.

"We expected to see some bad news and some good news," Woolf said. "But the U.S. ranked near and at the bottom in almost every heath indicator. That stunned us."