American Heart Month: A Physician and Epidemiologist Shares the 20th Century History of Coronary Heart Disease
February is American Heart Month. Organizations, like the American Heart Association, hold heart-health workshops during this month, as well as events to raise funds for research into the number one killer of men and women in the United States. Coronary heart disease (CHD) was the focus of a good part of the research my husband, Roger Sherwin, a physician and epidemiologist, conducted during his 45-year career in medicine and public health. Therefore, I asked him to share with my readers the history of CHD, which increased dramatically in the earlier years of the 20th century and fell dramatically in the later years, as well as the causes of these changes.
It may surprise most Americans (including many physicians) to learn that death rates from heart disease in middle-aged American men and women were approximately equal at the end of World War I (WW I). Shortly after WW I death rates from heart disease in middle-aged U.S. males began to rise sharply, while those in women declined. With the benefit of hindsight most of the early increase in heart disease in men was attributable to cigarette smoking, a habit brought back from Europe by U.S. servicemen, and associated particularly with sudden death from CHD. Despite the popular image of the 1920’s “flapper,” cigarette smoking among American women did not become common until women replaced men in factories during World War II.
Only at the end of the decade following WW I were the terms coronary heart disease (CHD) and myocardial infarction (heart attack) coined and entered on death certificates. Interestingly, death rates from CHD in Japan did not rise despite even greater rates of cigarette smoking among Japanese men than among American men. Again, with the benefit of hindsight and a great deal of research, it became clear why Japanese men reacted to smoking differently from American men: There was a large difference in the dietary consumption of animal fat between Japan and other East-Asian countries on the one hand and Western industrialized countries on the other. This much greater consumption of animal fat in the West led to substantially higher levels of “bad” low density lipoprotein (LDL) blood cholesterol. It now appears that a long-term level of LDL above about 100 mg/dl is a necessary condition for the gradual development of life-threatening plaques in the coronary arteries (coronary artery disease), leading to coronary heart disease.
Another important change occurred after WW I. In addition to the increase in cigarette smoking, physical activity both at work and in leisure among Americans declined. Heavy manual work was now largely replaced by work assisted by self-powered machines. In leisure, the mass production of motorcars flooding American towns and countryside was also associated with reduction of physical activity—but with less difference between men and women.
In addition to cigarette smoking, lack of exercise, and high levels of LDL cholesterol, a number of other risk factors are known to promote CHD. These include obesity (often the result of lack of exercise), high blood pressure, and diabetes. All of these risk factors are potentially modifiable. Others, including age, gender, and family history, are important but not modifiable.
Following the U.S. Surgeon General’s report on cigarette smoking and health in 1964, based largely on studies conducted in men, American men began to quit smoking, but American women continued to smoke. By the 1980s, therefore, more American women smoked than men. Accordingly, death rates from CHD in American men began to decline in 1967 and have continued to do so ever since, while death rates for American women began to decline much later and much less. Some of the decline in both sexes is, of course, attributable to public health education about the modifiable risk factors, which led in both men and women to less smoking, more exercise, heart-healthy diets, and treatment for high blood pressure with the safe and effective drugs that became available in the second half of the 20th century. Equally important were the great advances in the diagnosis and treatment of CHD, including resuscitation, rapid hospitalization, coronary care units, stents, bypass surgery, and the first really effective class of drugs to lower LDL, the statins, which can lower LDL to levels previously common only in the Far East. Statins are, of course, equally useful in the prevention as well as the treatment of CHD.
While CHD was described and diagnosed in the first half of the 20th century, only in the second half was successful prevention and treatment achieved, mainly by recognizing and modifying the causes of the disease. If cigarette smoking is largely a 20th century phenomenon, it has been replaced by an equally serious health problem—obesity. Thirty years ago about one-third of the U.S. population was overweight and half of those met the stricter definition of obesity. Today two-thirds of the U.S. adult population are overweight and half of those are obese—a 100 percent increase in both categories. Obesity is a risk factor for CHD through at least four different pathways: It leads to an increase in “bad” LDL cholesterol, a reduction in “good” high density lipoprotein (HDL) cholesterol, and an increase in blood pressure; in addition, it is the primary modifiable risk factor for diabetes. Unless the “epidemic” of obesity can be controlled, we may well see rates of CHD cease to decline or even increase as the century progresses.
My thanks to Google free images for the educational illustrations.