The largest declines were seen in heart disease and stroke, while death rates for diabetes and lung disease or chronic obstructive pulmonary disease (COPD) increased.
Cancer deaths also declined, but not nearly enough, stated the authors of the report, appearing in the Sept. 14 issue of the Journal of the American Medical Association.
"The death rate overall has fallen considerably," said Elizabeth Ward, co-author of the report and director of surveillance research in the department of epidemiology and surveillance research at the American Cancer Society in Atlanta. "Even though we've made progress in reducing the death rate overall, we actually have two causes of death that are continuing to rise."
On a more positive note, Americans are dying from these types of major illnesses at a later age, the report found.
Age-standardized death rates have, in fact, been decreasing since the 1960s. This year, for the first time, cancer displaced heart disease as the leading killer of Americans under the age of 85.
For Americans of all ages, however, heart disease remains the leading killer.
Ward and her colleagues examined trends in death rates from the nation's six leading causes of death: heart disease, stroke, cancer, COPD, accidents and diabetes.
They report that the age-standardized death rate fell from 1,242 per 100,000 per year in 1970 to 845 by 2002. Percentage-wise, the largest declines were in stroke (63 percent), heart disease (52 percent) and accidents (41 percent). In absolute numbers, the largest declines were in heart disease (262 deaths per 100,000) stroke (96 per 100,000) and accidents (26 per 100,000).
The death rate from all types of cancer combined rose between 1970 and 1990, then decreased from 1990 through 2002 for a net decline of 2.7 percent. "Even though it's declining currently, we would still like to see a great deal of progress in coming decades, because it certainly is declining less than heart disease," Ward said.
Death rates from COPD between 1970 and 2002 doubled, while those from diabetes increased by 45 percent since 1987.
According to the study authors, the decline in deaths from accidents seemed to stem from the introduction of the 55 mph speed limit and the mandated use of seat belts.
The increase in cancer death rates through 1990 probably reflected the continued toll of smoking, while the renewed success against cancer after 1990 reflected gains in tobacco control, as well as early detection and better treatment.
The continued increase in death rates from COPD are less well understood, Ward said, "but probably one contribution is the very long-term effects of cigarette smoking, when a person smoked earlier in life."
As for diabetes, more deaths may simply reflect a greater prevalence of the disease, said Dr. Stuart Weiss, a clinical assistant professor of medicine at New York University School of Medicine in New York City.
"All the data shows to me is that more people have more diabetes than before," he said.
Heart disease is the main success story here, experts said.
"This is part of a prevention revolution in the medications we have to prevent heart attack and stroke. They're easier to take and have less side effects," said Dr. Arthur Agatston, an associate professor of medicine at the University of Miami School of Medicine. "This is just the tip of the iceberg. It shows we can do a lot better in the next five to 10 years."
Some of these gains in heart disease may presage future gains in diabetes as well, "certainly with the recognition of pre-diabetes and weight control and the importance of exercise," Agatston said.
Reduced death rates from heart disease also reflect the decline in cigarette smoking, as well as improvements in screening or blood pressure and cholesterol, Ward added.
More information
The U.S. Centers for Disease Control and Prevention have more on death rates.
