The sharp decline in deaths from cardiovascular disease in the United States during the past two decades has been accompanied by an unexpected increase in the overall incidence of cancer and cancer deaths among people over 55, researchers say.
White men born during the baby boom of 1948-57 have non-smoking-related cancer rates three times as high as their grandfathers, but the rate of cardiovascular disease has fallen by 43 percent, a government research team reports today in the Journal of the American Medical Association.
White women in the same age group have 30 percent more cancer not related to smoking than their grandmothers, but 500 percent more cancer caused by smoking. "This increase is really alarming," said epidemiologist Devra Lee Davis of the U.S. Department of Health and Human Services, the primary author of the new report.
But the study also had some good news. The incidence of smoking-related cancer among men is down dramatically from its peak in the 1920s. "That's a major public health victory," said Edward Sondik, deputy director of NCI's Division of Cancer Prevention and Control.
The study also found that cancer mortality among people under the age of 55 decreased by 17 percent between 1973 and 1987, but increased by 12 percent among older people.
Other researchers expressed the need for caution in interpreting the cancer rates among older people.
Dr. Cary Presant, a professor of medicine at University of Southern California and chairman of the California Division of the American Cancer Society, said that when people do not die of heart disease, they live longer and have a higher risk of cancer. As a result of continuing improvements in controlling heart disease, he said, "by the year 2000, the leading cause of death will no longer be cardiovascular disease, but cancer."
Dr. Davis and her colleagues said they do not know the cause of the observed increases in the cancer rate but suspect it is due to growing exposure to both known and undiscerned carcinogens in the environment. One strong clue, Dr. Davis said, is that farm families show an even higher death rate from the forms of cancer that have shown the greatest increase in the general population.
Such families have high exposures to a variety of agents, including pesticides, herbicides, engine exhausts, chemical solvents, animal viruses and sunlight, that could be the cause of the observed increases in cancer rate, according to Dr. Davis.
"This study shows that we need a national commitment to public health research on the causes of these diseases that are increasing so that we can prevent them," Dr. Davis said.
The new study is based on data collected in the first 15 years of NCI's Surveillance, Epidemiology and End Results program, an ongoing project in which actual cancer rates are determined in a representative 10 percent of the U.S. population.
The researchers focused solely on whites, Dr. Davis said, because "blacks and other minorities do not have equal access to health care." Cancer and other diseases are less likely to be diagnosed at an early stage in blacks than in whites now, she noted, and were much less likely to be diagnosed in the past. "We didn't think it worthwhile to analyze the data [on blacks] because we might see an increase that wasn't real."