[ Pobierz całość w formacie PDF ]
.6Evidence of a 1960 date for the decline is also found in studies ofcoronary heart disease morbidity and mortality.A nationwide study exam-ined 75,000 to 94,000 male employees of the E.I.DuPont de Nemoursand Company from 1957 to 1983.About 95% were covered by healthinsurance, which suggests generally accurate diagnoses.The age-adjustedrates of first myocardial infarctions and sudden deaths attributed to coro-nary heart disease per 1,000 employees declined from 3.2 in 1957 59 to3.1 in 1960 62, 2.9 in 1963 65, and 3.0 in 1966 68.A steeper rate ofdecline then occurred to 2.7 in 1969 71 and 2.3 in 1981 83.Rates for thehigher-paid salaried workers declined earlier and to a greater extent thanfor the lower-paid wage workers.Another study of the incidence of initialmyocardial infarctions, angina pectoris, and sudden unexpected deaths inresidents of Rochester, Minnesota, from 1950 through 1982 found thatthe rate peaked for men in the 1950s and declined steadily thereafter.Thedecline occurred primarily among those ages 30 69.The trends were muchweaker among women, whose rates were about one-fourth those of men atages 30 49 and one-half at older age groups.7Other evidence that healthy persons were the primary beneficiaries ofthe decline consists of a downward trend in mortality rates of persons with-out preexisting heart disease, while no such trend occurred in persons withpreexisting disease up to the late 1980s.A community-wide study exam-ined 793 validated coronary heart disease deaths among white males ages35 44 in the Pittsburgh, Pennsylvania, area between 1970 and 1981.Theage group was chosen because of its high autopsy rate and the infrequencyof previous coronary heart disease.From 1970 72 to 1979 81 the groupexperienced a 50% decline in coronary heart disease mortality rates, pri-marily due to fewer new cases of the disease.The greatest decline occurredfor sudden coronary heart disease deaths without a previous history of coro-nary heart disease.In addition, out-of-hospital deaths and cases who were deadon arrival declined by 62%, while in-hospital deaths declined by only 33%.8Studies elsewhere produced similar findings.Sixteen hospitals in theWorcester, Massachusetts, metropolitan area experienced a steady decreasein death rates from initial acute myocardial infarction and in out-of-hospi-tal deaths from coronary heart disease for both men and women between1975 and 1988.No changes occurred for in-hospital death rates or survivalrates of patients discharged from the hospitals after acute myocardialinfarctions.A study of one million subscribers to the Kaiser-Permanentehealth plan in northern California from 1971 to 1977 found that the down-The Secular Decline in the Coronary Heart Disease Epidemic 351ward trend in coronary heart disease mortality rates was due to fewer newcases rather than higher survival rates of those with the disease.A New YorkCity study of first myocardial infarctions compared the 4.5 year post-hos-pitalization survival rates of 436 men ages 35 64 in 1961 70 to 697 menin 1971 80.Although this was a period of steadily declining coronary heartdisease mortality rates, no differences in survival rates occurred betweenthe two groups or between subgroups that had infarctions of the same de-gree of severity.9These studies provide convincing evidence that about 1960 rates offirst myocardial infarctions and coronary heart disease mortality began todecline steadily in healthy men.The study samples varied widely in com-position and geographic locations.The onset of the decline occurred dur-ing a single revision of the International Classification of Diseases, therebyeliminated classification changes as a possible explanation.Coronary heartdisease mortality rates for women declined later than those for men, butthe pandemic was much milder for women.The coronary heart disease pandemic occurred during the same timeperiod in North America, western and northern Europe, Australia, andother advanced westernized countries.These countries experienced steadilyincreasing coronary heart disease mortality rates for men from the 1920sthrough the 1960s.After about 1970, practically all of them experiencedsteadily declining rates for both men and women.The gender patterns ofthe pandemic were very similar in all of the countries.10Trends in Risk Factors and Coronary Heart Disease RatesCoronary heart disease is produced by a combination of factors that inter-act and operate in the human body over years or decades.Changes in thecausal factors must therefore occur long before the onset of the decline.Ifthe decline in coronary heart disease rates in healthy men began about1960, their risk factors must have begun changing no later than the early1950s.Proponents of the risk factor theory describe three types of changes:(1) new treatments for persons who experienced coronary heart disease; (2)modifications of risk factors in persons at high risk of the disease; and (3)modifications of risk factors in the general population.Improvements in the treatment of coronary heart disease made nocontribution to the decline in mortality rates until long after 1960.Mostinnovations in treatment became widely used in the 1970s or 1980s, in-cluding prehospital resuscitation, coronary artery bypass graft surgery,352 Risk Factors and Coronary Heart Diseaseangioplasty, thrombolytic therapy, and drugs such as beta-blockers.An-other widely cited intervention, the coronary care unit, was developed inthe early 1960s to treat potentially fatal heart arrhythmias in patients withrecent myocardial infarctions.By 1966, 350 units were in operation andthousands more were established in the next decade.These units were gen-erally ineffective during the 1960s and 1970s: many patients in them weremisdiagnosed, the staffs were untrained and often lacked authority to treatpatients immediately, and resuscitation was soon found to be less usefulthan prevention of arrhythmias.Studies in England found little benefit ofthe units for patients with mild or moderate myocardial infarctions.11 Fur-thermore, therapeutic innovations were implemented at different times andto widely varying degrees in the countries that experienced similar declinesin coronary heart disease mortality.More generally, no major epidemic hasever been halted by therapeutic innovations, but only by preventive mea-sures and changes in social and environmental conditions.Modification of risk factors in high risk persons did not contribute tothe secular decline that began about 1960 [ Pobierz całość w formacie PDF ]