By Matt Brignall, ND
Healthnotes Newswire —Improvements in diet and a reduction in smoking are the primary factors responsible for a significant decrease in heart disease risk during a 14-year period, according to a study published in today’s New England Journal of Medicine.1 The incidence of heart disease among 85,000 American nurses was reported to have dropped by 31% between 1980 and 1994. While the death rates from heart disease in America have clearly been falling for the last three decades, it has been somewhat unclear whether this is due to declines in the disease itself or to improved treatment.2 3
Two-thirds of this decline appeared to be due to three factors: a reduction in smoking, an increased use of hormone replacement therapy (HRT), and an improved diet. A 13% drop in the risk of heart disease was attributed to a 41% decline in the percentage of nurses who smoked at the end of the study compared with the beginning. Postmenopausal HRT prescriptions increased by 175%, and this increase was associated with a 9% decrease in heart disease. The largest decline in coronary artery disease risk, a decrease of 16%, was associated with improvement in diet. The percentage of nurses who were obese increased from 37 to 51%, however, which was associated with an 8% increase in risk. Given the effect of this increased incidence of obesity, the 31% drop in overall risk of heart disease was all the more remarkable.
The dietary changes reported included increased intake of cereal fiber (90%), omega-3 fatty acids from fish (180%), and folic acid (12%); increased ratio of polyunsaturated to saturated fatty acids (69%); and decreased intake of trans-fatty acids (31%). (Folic acid content of fruits and vegetables is high; polyunsaturated fats are found in vegetable oils, nuts, and seeds; and trans-fatty acids are found in margarine and processed foods containing partially hydrogenated oils.)
The only measurement that reflected a worsening diet was a 22% increase in glycemic load, a measurement of increases in blood sugar levels in response to specific foods. Foods high in fiber tend to produce low (good) glycemic loads, and foods high in sugar or starch in the absence of high fiber tend to produce high (unhealthful) glycemic loads.
Compared with diets recorded in 1980, diets assessed in 1994 contained more fish, whole grains, and fresh fruits and vegetables. They also contained less animal fat (particularly from beef and dairy) and trans-fatty acids. On the other hand, increases in sugary foods, and possibly an increase in calories, were reflected in the increasing incidence of obesity.
The authors of this new study attribute part of the reduced heart disease risk to increased use of HRT. While many doctors believe HRT prevents heart attacks, there is surprising little research proving a benefit. Instead, the results of several new trials,4 5 including one also published in today’s New England Journal of Medicine,6 strongly suggest that HRT does not protect against heart disease. Previous preliminary studies have found that women who chose to take HRT typically have a low risk of heart disease, as found in the new Nurses' Health Study report.7 8 However, this association appears to result from lifestyle factors found more commonly in these women than in women who do not take HRT. In other words, in these women, HRT use appears to only be a marker for other protective behaviors.9
These results support the findings of a study in the July 6, 2000, edition of the New England Journal of Medicine previously discussed in Healthnotes Newswire.10 In that report, which analyzed the data from the same nurses, women with none of the lifestyle risk factors that were studied had an 83% reduction in heart disease incidence compared to all other women. The factors that were analyzed included the effects of smoking, obesity, exercise, alcohol moderation, and diet on the risk of heart disease. The dietary variables were the same ones examined in the new study.
Even with the apparent reduction in heart disease risk noted in this study, heart attack remains the number one killer of American women. The results of the studies reported here constitute the best indication that the risk of heart disease can be dramatically reduced with basic diet and lifestyle changes. Except for controlling excess body weight, American women appear to be making some of the changes necessary to reduce heart disease risk.
The researchers note that nurses may be more health conscious than the population as a whole, and therefore these hopeful findings may be more impressive than the decreases in the risk of heart disease experienced by other Americans. Nevertheless, these data support the notion that heart disease risk––not only the death rate due to heart disease––is going down.
References1. Hu FB, Stampfer MJ, Manson JE, et al. Trends in the incidence of coronary heart disease and changes in diet and lifestyle in women. N Engl J Med 2000;343:530–7.
2. McGovern PG, Pankow JS, Shahar E, et al. Recent trends in acute coronary heart disease: mortality, morbidity, medical care, and risk factors. N Engl J Med 1996;334:884–90.
3. Rosamond WD, Chambless LE, Folsom AR, et al. Trends in the incidence of myocardial infarction and in mortality due to coronary heart disease, 1987 to 1994. N Engl J Med 1998;339:861–7.
4. Hulley S, Grady D, Bush T, et al. Randomized trial of estrogen plus progestin for secondary prevention of coronary heart disease in postmenopausal women. Heart and Estrogen/progestin Replacement Study (HERS) Research Group. JAMA 1998;280:605–13.
5. The Writing Group for the PEPI Trial. Effects of estrogen or estrogen/progestin regimens on heart disease risk factors in postmenopausal women. The Postmenopausal Estrogen/Progestin Interventions (PEPI) Trial. JAMA 1995;273:199–208.
6. Herrington DM, Reboussin DM, Brosnihan KB, et al. Effects of estrogen replacement on the progression of coronary-artery atherosclerosis. N Engl J Med 2000;343:522–9.
7. Stampfer MJ, Colditz GA, Willett WC, et al. Postmenopausal estrogen therapy and cardiovascular disease: ten years’ follow-up from the Nurses’ Health Study. N Engl J Med 1991;325:756–62.
8. Grady D, Rubin SM, Petitti DB, et al. Hormone therapy to prevent disease and prolong life in postmenopausal women. Ann Intern Med 1992;117:1016–37.
9. Gaby AR. Does estrogen replacement therapy prevent heart disease? Townsend Letter for Doctors and Patients 2000;Aug/Sept:108–9 [editorial].
10. Stampfer MJ, Hu FB, Manson JE, et al. Primary prevention of coronary heart disease in women through diet and lifestyle. N Engl J Med 2000;343:16–22. Matt Brignall, ND, is a research associate at the Tahoma Clinic in Kent, Washington, and a contributor to the Healthnotes Review of Complementary and Integrative Medicine and Healthnotes Online.