Serum cholesterol, diet, and the decline in coronary heart disease mortality

Contribution of changes in risk factors to the decline of coronary heart disease mortality in Australia over three decades

BACKGROUND

Coronary heart disease has been a major cause of mortality in Australian adults, but the rate has declined by 83% from the 1968 peak by the year 2000. The study objective is to determine the contribution of changes in population risk factors - mean serum cholesterol and diastolic blood pressure and tobacco smoking prevalence - to the decline in coronary heart disease mortality in Australia over three decades.

METHODS

Coronary heart disease deaths (International Classification of Disease-9, 410-414) and population by year, age group and sex were obtained from the Australian Bureau of Statistics. Risk factor levels were obtained from population surveys and estimated average annual changes by period were used to calculate average annual 'attributable' proportional declines in CHD mortality by period (age 35-64 years).

RESULTS

Over the period 1968-2000, 74% of male decline and 81% of the female decline in coronary heart disease mortality rate was accounted for by the combined effect of reductions in the three risk factors. In males 36% of the decline was contributed by reductions in diastolic blood pressure, 22% by cholesterol and 16% by smoking. For females 56% was from diastolic blood pressure reduction, 20% from cholesterol and 5% from smoking. Effects of reductions in serum cholesterol on coronary heart disease mortality occurred mainly in the 1970s. Declines in diastolic blood pressure had effects on coronary heart disease mortality over the three decades, and declines in tobacco smoking had a significant effect in males in the 1980s.

CONCLUSION

Most of the spectacular decline in coronary heart disease mortality over the last three decades in Australia can be ascribed to reductions in population risk factors from primary and secondary prevention.

The contributions of prevention and treatment to the decline in cardiovascular mortality: lessons from a forty-year debate

Mortality from coronary heart disease in the United States has fallen 60 percent from its peak in the mid-1960s. Cardiologists and epidemiologists have debated whether this decline reflects better control of risk factors, including lifestyle interventions to reduce smoking or intake of dietary fats, or the power of medical interventions, including defibrillators and therapeutics such as statins. Attempts to resolve this debate and guide health policy have generated sophisticated data sets and techniques for modeling cardiovascular mortality. Neither effort has provided specific guidance for health policy. Historical analysis of the debate over the causes of the decline, concomitant with development of cardiovascular modeling, offers valuable policy lessons about tensions among medical and public health strategies, the changing meanings of disease prevention, and the ability of evidence-based research and models to guide health policy. Policy makers must learn to open up the "black box" of epidemiological models-and of their own decision-making processes-to produce the best evidence-informed policy.

Changing patterns of coronary heart disease in the hunter region of New South Wales, Australia

A population-based observational study of men and women aged 35-69 years in the Hunter Region of New South Wales, Australia, was conducted to assess the impact of risk-factor modification and increased drug therapy on the trends in major coronary events and case fatality. From 1985 to 1993, there were 3006 coronary deaths and 6450 nonfatal major coronary events. Rates of death and nonfatal myocardial infarction declined, but there was an increase in hospital admissions for prolonged chest pain. Reductions in cigarette smoking, diastolic blood pressure, total cholesterol, and increased use of aspirin can fully explain the 3.3% (95% confidence interval [CI] 2.4, 4.2) average annual reduction in rates of major coronary events for men and the 4.1% (95% CI 2.7, 5.5) reduction for women. In contrast, increased use of aspirin, beta-blockers, fibrinolytic therapy, and angiotensin-converting enzyme inhibitors explain less than half of the 8.9% (95% CI 5.9, 11.8) and 6.9% (95% CI 2.7, 10.9) average annual reduction in case fatality in hospital for men and women, respectively. These trends suggest a decline in severity of coronary heart disease consistent with reductions in risk-factor levels and improved acute medical treatment.

Changing prevalence of coronary heart disease risk factors and cardiovascular diseases in men of a rural area of Crete from 1960 to 1991

This study compares the prevalence of coronary heart disease (CHD), risk factors (RF), and cardiovascular diseases (CVD) among Cretan men from a rural area examined in 1960 and 1991. The study population consisted of 148 men in 1960 and 42 men in 1991 of the same age group (fifty-five to fifty-nine years old) and from the same rural area. All men had a complete examination of the cardiovascular system and a resting electrocardiogram (ECG). Systolic BP (SBP) > or = 140 mmHg was found in 42.6% of the subjects in 1960 and in 45.2% in 1991 (NS). Diastolic BP > or = 95 mmHG was found in 14.9% of the subjects in 1960 as opposed to 33.3% in 1991 (P < 0.02). Total serum cholesterol (TSCH) > or = 260 mg/dL approximately 6.7 mmol/L) was found in 12.8% of the subjects in 1960 and in 28.6% in 1991 (P < 0.01). Heavy smokers ( > or = 20 cigarettes/daily) were 27.0% in 1960 as compared with 35.7% in 1991 (:NS); 5.4% of the subjects in 1960 had light physical activity (PA) as compared with 14.3% in 1991 (P < 0.01); 74.7% of the subjects were farmers in 1960 as compared with 43.6% in 1991 (P < 0.1). The prevalence of CHD was 0.7% in 1960 as compared with 9.5% in 1991 (P < 0.001). Hypertensive heart disease was found in 3.4% of the subjects in 1960 and 4.8% in 1991 (NS). The prevalence of all major CVD was much higher in 1991 (19.1%) as compared with 1960 (8.8%) (P < 0.01). In conclusion, the prevalence of CHD RF and CVD was much higher in 1991 than in 1960 for Cretan men of the same age group. This higher prevalence seems to be related to dietary and life-style changes that have taken place in Crete during the last thirty years.

The quality of epidemiological data in coronary heart disease and atherosclerosis

There are inherent difficulties in the use of indirect observations in the epidemiology of a chronic ubiquitous disease such as atherosclerosis. Such difficulties do not condone basic errors in epidemiological methodology, the use of low quality data, a lack of precision in measurements, invalid extrapolations and inappropriate use of terminology and coronary heart disease as a surrogate or synonym of coronary atherosclerosis and bias in the interpretation of data. These errors reveal a lack of rigorous and scientific standards in the epidemiology of coronary heart disease. Analysis cannot launder such data. Independent scientists must evaluate the data in respect of precision, logic and truth.

Public health implications of dietary differences between social status and occupational category groups

STUDY OBJECTIVE

As there is a social status gradient in chronic disease mortality in Australia, this study aimed to establish whether there were substantial differences among socioeconomically defined groups with respect to food choice and nutrient intake, in the context of risk of nutrition related chronic diseases.

DESIGN AND PARTICIPANTS

Cross sectional data were collected from a randomly selected population sample of 1500 urban Australian adults. Data were collected by postal questionnaire, which included an assessment of dietary intake and questions on sociodemographic details. Three measures of social position were collected: occupation, educational status, and income status. Occupation was interpreted both on a continuous, prestige scale, and also as categorical occupational groupings.

MAIN RESULTS

The study achieved a 70% response rate. Higher social status was generally associated with healthier dietary intakes, with lower fat and refined sugar densities, and higher fibre densities, but also with higher alcohol density. No differences were found in salt, polyunsaturated fat, protein, or complex carbohydrate densities across groups. Food intake differences were also found between occupational status groups, with the upper social groups tending to consume more wholegrain cereal foods, low fat milk, and fruit, and less refined cereal foods, full cream milk, fried meat, meat products, and discretionary sugar; but also more cheese and meat dishes.

CONCLUSIONS

Although this study did show statistically significant differences across social status groups in relation to nutrient and food intakes, these differences were small compared to the disparity between intakes of all groups and the recommended patterns of intake, and did not appear to be great enough to be a major explanatory variable in differences in disease risk across groups.

Socioenvironmental characteristics associated with the onset of decline of ischemic heart disease mortality in the United States

The relation of community socioenvironmental characteristics to timing of the onset of decline of ischemic heart disease (IHD) mortality was investigated among the 507 State Economic Areas of the continental United States. Onset of decline was measured using data for White men aged 35-74 and classified as early (1968 or before) vs late (after 1968). Ten socioenvironmental characteristics derived from US Census Bureau data were strongly related to onset of decline. Areas with the poorest socioenvironmental conditions were two to 10 times more likely to experience late onset than those areas with the highest levels. We found that income-related characteristics could account for most of the difference in onset of decline of IHD between metropolitan and non-metropolitan places. We conclude that community socioenvironmental characteristics provide the context for changes in risk factors and medical care.

The advisability of the prudent diet in adolescence

Risk factor status for cardiovascular disease is affected by life style. Adolescence is a time during which long term life-style habits, including dietary habits, are established. Physicians who treat adolescent patients have a responsibility to be aware of the scientific evidence on the diet-heart question so that they can provide their patients with sound dietary advice. The American Heart Association has recommended that Americans consume a "prudent diet" in which daily consumption of cholesterol is no more than 300 mg with up to 30-35% of calories derived from fat, and less than 10% of calories derived from saturated fat and less than 10% from polyunsaturated fat. This paper reviews this recommendation with particular reference to studies of adolescents. This review centers around four main issues: 1) the estimated effect on serum cholesterol levels of a switch from the usual American diet to the prudent diet; 2) the effect of a predicted decrease in serum cholesterol on the risk of developing cardiovascular disease; 3) evaluation of the evidence of possible adverse effects of the prudent diet; 4) feasibility of the prudent diet. Based on a review of these four issues, the authors feel that the American Heart Association's prudent diet should be strongly recommended for all healthy adolescents.

Cholesterol and cardiovascular disease. An overview of Lipid Research Clinics (LRC) epidemiologic studies as background for the LRC Coronary Primary Prevention Trial

The Lipid Research Clinics (LRC) Program has implemented an integrated series of observational epidemiologic, community-based studies that provide a frame of reference for the results of the LRC Coronary Primary Prevention Trial (CPPT). The observational studies were performed in 16 populations sampled in the United States, Canada, the Soviet Union and Israel. Findings based on data from more than 80,000 study participants indicate that atherogenic profiles of plasma total, low-density lipoprotein and high-density lipoprotein cholesterol levels are highly prevalent in middle-aged adults. The lipoprotein cholesterol fraction components are related to a wide range of demographic, behavioral, anthropometric, medical status, drug utilization and hormonal factors, in addition to the well known major dietary and genetic determinants. The results of the LRC CPPT are directly applicable to high-risk, high total cholesterol, and high low-density lipoprotein cholesterol levels in middle-aged men. Considered jointly with the observational finding that the major burden of ischemic heart disease is associated with moderately elevated lipid levels, the LRC studies suggest that 2 concurrent approaches are necessary to achieve community control: approaches for high-risk person through individualized medical intervention and hygienic, population-oriented approaches toward achieving less atherogenic distributions of lipids and lipoproteins. With this combined approach, the current epidemic of ischemic heart disease can be controlled.

Decline in coronary heart disease mortality. Old questions and new facts

By 1979, mortality rates for coronary heart disease had declined for 14 consecutive years in the United States. Preliminary data indicate a continued decline. This review of reports published in the last five years documents the consistency of most data with the following hypotheses: (1) Reductions in population levels of hypertension and cigarette smoking have contributed to the decline in mortality from coronary heart disease. (2) Improved medical care for acute myocardial infarction has also contributed to the decline. Data are lacking to specify the contributions of changes in other risk factors, emergency medical services, medical care of chronic coronary heart disease, or other changes in the physical and social environment. Long-term, simultaneous surveillance of mortality, morbidity, medical care, and risk factors should be supported in five to 10 centers around the United States.

Randomized controlled trial of a nonpharmacologic cholesterol reduction program at the worksite

Under experimental clinical conditions diet modification has been shown to reduce serum cholesterol levels. This paper reports such a positive response to a nonpharmacologic, behavioral education program at the worksite. Employees at the New York Telephone Company corporate headquarters were assigned randomly to treatment and control groups. Treatment consisted of an 8-week group cholesterol reduction program conducted during employee lunch hours. It comprised a multiple-treatment approach--food behavior change techniques combined with nutrition education, physical activity planning, and self-management skills. The treatment group showed substantial change compared with the control group at the program's completion. Those treated displayed a significant 6.4% reduction in total serum cholesterol (266 mg% average at baseline) as compared with control subjects with a corresponding decrease in high-density lipoprotein levels. A significant increase in nutrition knowledge and moderate weight loss were also documented for this group. The magnitudes of a participant's baseline serum cholesterol level and his/her reduction in percentage of ideal body weight were positively and independently correlated with percentage changes in serum cholesterol levels. Over the same period, decreases in high-density lipoprotein levels and no changes in serum cholesterol, weight, and nutrition knowledge were observed for the control group. Overall, participants in the treatment program successfully reduced the coronary heart disease risk factors of elevated cholesterol and weight. Directions for future study are suggested.

Absence of secular changes in the prognosis of patients with an initial myocardial infarction

A community-based study was conducted in metropolitan Baltimore in which secular trends in the in-hospital and long-term prognosis of 935 male and female patients hospitalized with an initial myocardial infarction were examined for the two periods of 1966-1967 and 1971. The in-hospital case fatality rate among males in both periods remained unchanged (19.0% vs 19.0%), whereas there was a decrease over time among women hospitalized in 1966-1967 as compared to those in 1971 (37.2% vs 26.6%) (p less than 0.10). For patients discharged alive from the hospital and followed up for as long as 10 years, no significant differences in overall survival were observed between male patients discharged in 1966-1967 and 1971 or between female patients discharged in these two periods. These findings may reflect the lack of major therapeutic advances in the care of the acute coronary patient between the two study periods and, therefore, support continuing efforts directed at the primary and secondary prevention of the atherosclerotic process.

Dietary intake and serum total cholesterol level: their relationship to different lifestyles in several Japanese populations

Serum total cholesterol level and dietary intake were surveyed 1975--1977 in six Japanese population groups with different lifestyles, including groups in both rural (Akita and Kochi) and urban (Osaka) areas. Clerical workers in Osaka, who had the most westernized lifestyle of all the study groups, had the highest mean serum total cholesterol level (202 mg/dl for men ages 40--49 and 50--59 years), while farmers in Akita had the lowest mean serum total cholesterol level (163 mg/dl for men 40--49 years old, 159 mg/dl for men 50--59 years old, 165 mg/dl for men 60--69 years old). Nutrient intake data for mean ages 40--59 years showed 23% of calories from fat for clerical workers in Osaka, the highest among the study groups, whereas farmers in Akita showed a low level of 14%. The ratio of dietary polyunsaturated to saturated fatty acids was over 1.1 for all groups. Cholesterol intake was 339--487 mg/day. Total carbohydrate as a percentage of calories was 53--65%; 75--80% of carbohydrate energy was ingested from cereals. Sugar accounted for less than 3.5% of total calories. In the cross-group correlation analysis between dietary lipid intake and serum total cholesterol, a significant strong positive correlation was found between the dietary lipid factor (phi) of Keys et al. and the mean serum total cholesterol level. A weak but significant correlation was observed between the dietary lipid factor and serum total cholesterol for individual inhabitants of Osaka.

Recent trends in coronary risk factors in the USSR

The soviet Union has experienced an increase in the incidence of coronary heart disease over the last 15 years sufficient to result in an overall deterioration in the health of adults. The distribution of coronary risk factors, and the secular trends in diet and cigarette consumption, provide a potential explanation for the upsurge in death rates. The animal fat content of the Soviet diet has been steadily enriched since the 1950s and cigarette production increased 72 per cent from 1959 to 1980. The post-Stalin orientation of the Soviet economy toward a policy of motivating the work force primarily through the provision of consumer goods, in a pattern comparable to western capitalist countries, appear to have laid the basis for these developments. Given the central control of Soviet society, the negative impact of current economic policy on the public health could be viewed as paradoxical. Our analysis suggests that the paradox is only apparent, however, and that the basis for the widespread occurrence of coronary heart disease is similar in the Soviet Union and western societies.

Current strategies for explaining the decline in ischemic heart disease mortality

Mortality from ischemic heart disease has declined sharply since the mid 1960's in the United States and several other industrialized nations. The causes of this decline have thus far not been established. Six major strategies for investigating determinants of ischemic heart disease mortality trends are discussed in this review: (1) analyses of mortality data; (2) morbidity surveillance; (3) surveillance of change in medical care; (4) surveillance of cardiovascular risk factors; (5) social and ecological surveillance; (6) experimental and quasi-experimental community approaches. The rationale, problems and limitations of each are discussed.

A multiple cause of death analysis of hypertension-related mortality in North Carolina, 1968-1977

In this paper, records of all medical conditions on death certificates are used to evaluate hypertension-related mortality in North Carolina over the decade 1968-1977. Use of both an inclusive hypertension recode category and multiple cause data resulted in gains in information of over 750 per cent in all four race/sex groups compared to the commonly used underlying cause, hypertensive disease category. Race, sex and age specific 10-year trends in death rates for all mentions of hypertension are analyzed, with comparisons to underlying cause mortality from ischemic heart disease and stroke. Age-adjusted declines of 19 to 24 per cent between 1968 and 1977 were observed for all race/sex groups, although non-White declines occurred mainly at younger ages while White declines (especially White males) occurred mainly at older ages. The non-White excess of hypertension mentions (compared to Whites) increased for males and decreased for females. The decline in hypertension mentions, in spite of the increased awareness of hypertension as a public health problem which would make it more likely to be mentioned on death certificates, suggests that there was a real reduction in the contribution of hypertension to total mortality over the period.

Rising death rates in the Soviet Union: the impact of coronary heart disease

Age-adjusted overall death rates in men and women in the Soviet Union began to rise in the mid-1960s; an 18 per cent increase occurred in the entire population from 1964 to 1975. The epidemic of coronary heart disease (CHD) appears to be the primary cause of this trend and has been particularly widespread among middle-aged men. Prospective epidemiologic studies and autopsy reports confirm the high prevalence rates of atherosclerosis and its complications. The major risk factors for CHD occur frequently in the Soviet population. The epidemic nature of the modern chronic diseases is dramatically apparent in the secular trends in Soviet vital statistics. A similar pattern of life style as related to risk of CHD in the Soviet Union and in Western capitalist countries further suggests a similar social basis for this epidemic in both areas.