Cancer has overtaken heart disease as the leading killer of middle-age Americans, researchers reported.

Meanwhile, the overall death rate among Americans dropped sharply - 35.6 percent - between 1950 and 1986, falling from 841.5 deaths per 100, 000 people to 541.7 deaths per 100,000 people, the Southern Illinois School of Medicine researchers said Tuesday."It is evident that the patterns of proportionate mortality in the United States are changing," the researchers wrote in the Journal of the American Medical Association.

"We are `dying differently,' both because of the progress in preventing and treating specific diseases and because of the resultant changes in demographics resulting from postponing death to a later age," they said.

The researchers analyzed National Center for Health Statistics data on U.S. death rates from 1950 to 1986, tracking illnesses that are or had been the six leading causes of death.

The overall death rate drop was caused by a decline in deaths from such killers as cerebrovascular diseases, injuries, childbirth complications, the flu and pneumonia, the researchers said.

During the same period, however, the proportion of deaths increased "dramatically" for chronic obstructive pulmonary disease and cancer, both of which are often caused by smoking cigarettes.

In fact, for those ages 35 to 64, cancer has "now overtaken heart disease as the leading cause of death," they said, adding that "if trends continue, it could overtake heart disease for those aged 65 to 74 years."