The Epidemic That Wasn't?
For half a century, nutritionists have pointed to soaring death rates as the genesis of their research into dietary fat and heart disease and as reason to advise Americans to eat less fat (see main text). "We had an epidemic of heart disease after World War II," obesity expert Jules Hirsch of Rockefeller University in New York City said just 3 months ago in The New York Times. "The rates were growing higher and higher, and people became suddenly aware of that, and that diet was a factor."
To proponents of the antifat message, this heart disease epidemic has always been an indisputable reality. Yet, to the statisticians at the mortality branch of the National Center for Health Statistics (NCHS), the source of all the relevant statistics, the epidemic was illusory. In their view, heart disease deaths have been steadily declining since the late 1940s.
According to Harry Rosenberg, director of the NCHS mortality branch since 1977, the key factor in the apparent epidemic, paradoxically, was a healthier American population. By the 1950s, premature deaths from infectious diseases and nutritional deficiencies had been all but eliminated, which left more Americans living long enough to die of chronic diseases such as heart disease. In other words, the actual risk of dying from a heart attack at any particular age remained unchanged: Rather, the rising number of 50-year-olds dropping dead of heart attacks was primarily due to the rising number of 50-year-olds.
The secondary factor was an increase from 1948 to 1968 in the probability that a death would be classified on a death certificate as arteriosclerotic disease or coronary heart disease. This increase, however, was a figment of new diagnostic technologies--the wider use of electrocardiograms, for instance--and the changing terminology of death certificates. In 1949, the International Classification of Diseases (ICD) added a new category, "arteriosclerotic heart disease," under the more general rubric "diseases of the heart." The result, as a 1958 report to the American Heart Association noted, was dramatic: "In one year, 1948 to 1949, the effect of this revision was to raise coronary disease death rates by about 20% for white males and about 35% for white females." In 1965, the ICD added a category for coronary heart disease, which added yet more deaths and capped off the apparent epidemic.
To Rosenberg and others at NCHS, the most likely explanation for the postwar upsurge in coronary heart disease deaths is that physicians slowly caught on to the new terminology and changed the wording on death certificates. "There is absolutely no evidence that there was an epidemic," says Rosenberg.
Related articles in Science:
The Soft Science of Dietary Fat.
Science 2001 291: 2536-2545.
(in News Focus)
- What If Americans Ate Less Saturated Fat?.
Science 2001 291: 2538.
(in News Focus)
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Issue of 30 Mar 2001,
Copyright © 2001 by The American Association for the Advancement of Science.