The Framingham Heart Study and the epidemiology of cardiovascular disease: a historical perspective

On Sept 29, 2013, the Framingham Heart Study will celebrate 65 years since the examination of the first volunteer in 1948. During this period, the study has provided substantial insight into the epidemiology and risk factors of cardiovascular disease. The origins of the study are closely linked to the cardiovascular health of President Franklin D Roosevelt and his premature death from hypertensive heart disease and stroke in 1945. In this Review we describe the events leading to the foundation of the Framingham Heart Study, and provide a brief historical overview of selected contributions from the study.

The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic

OBJECTIVE

Field studies of twentieth century hunter-gathers (HG) showed them to be generally free of the signs and symptoms of cardiovascular disease (CVD). Consequently, the characterization of HG diets may have important implications in designing therapeutic diets that reduce the risk for CVD in Westernized societies. Based upon limited ethnographic data (n=58 HG societies) and a single quantitative dietary study, it has been commonly inferred that gathered plant foods provided the dominant energy source in HG diets.

METHOD AND RESULTS

In this review we have analyzed the 13 known quantitative dietary studies of HG and demonstrate that animal food actually provided the dominant (65%) energy source, while gathered plant foods comprised the remainder (35%). This data is consistent with a more recent, comprehensive review of the entire ethnographic data (n=229 HG societies) that showed the mean subsistence dependence upon gathered plant foods was 32%, whereas it was 68% for animal foods. Other evidence, including isotopic analyses of Paleolithic hominid collagen tissue, reductions in hominid gut size, low activity levels of certain enzymes, and optimal foraging data all point toward a long history of meat-based diets in our species. Because increasing meat consumption in Western diets is frequently associated with increased risk for CVD mortality, it is seemingly paradoxical that HG societies, who consume the majority of their energy from animal food, have been shown to be relatively free of the signs and symptoms of CVD.

CONCLUSION

The high reliance upon animal-based foods would not have necessarily elicited unfavorable blood lipid profiles because of the hypolipidemic effects of high dietary protein (19-35% energy) and the relatively low level of dietary carbohydrate (22-40% energy). Although fat intake (28-58% energy) would have been similar to or higher than that found in Western diets, it is likely that important qualitative differences in fat intake, including relatively high levels of MUFA and PUFA and a lower omega-6/omega-3 fatty acid ratio, would have served to inhibit the development of CVD. Other dietary characteristics including high intakes of antioxidants, fiber, vitamins and phytochemicals along with a low salt intake may have operated synergistically with lifestyle characteristics (more exercise, less stress and no smoking) to further deter the development of CVD.

Nitric oxide and the endothelium: history and impact on cardiovascular disease

There are few discoveries with the magnitude of the impact that NO has had on biology during the 25 years since its discovery. There is hardly a disease today not associated with altered NO homeostasis. In fact, despite numerous other endothelial functions, endothelial dysfunction has become synonymous with reduced biological activity of NO. Translating the preclinical discoveries in NO biology to new modalities for disease management has not been as impressive. Beyond the success of drugs for erectile dysfunction, clinical trials of nitric oxide synthase inhibitor have been proven either ineffective or wrought with side effects. NO donors (e.g., nitroglycerine) remain frequently used cardiovascular agents, but were discovered before 1980. Gene therapy studies have yet to become clinically useful. There is no doubt that endothelial- and NO-dysfunction is a hallmark of cardiovascular disease, including diseases which are considered as major current public health concerns: hypertension, obesity, diabetes, malnutrition. In many cases, cardiovascular disease (CVD) can be prevented by identifying and controlling modifiable risk factors. One conceivable approach to the management of multiple risk factors in CVD could be to treat endothelial dysfunction (e.g., by enhancing eNOS expression), since many CVD risk factors are related to endothelial dysfunction. In this regard one goal may include optimizing eNOS function. This can be realized by supplementing co-factors, e.g., BH4, or substrate, L-arginine, by increasing cGMP availability via phosphodiesterase inhibitors or sGC activators or by increasing NO bioavailability via antioxidants. The association of other proteins with the nitric oxide synthase (NOS) isoforms and sGC could also serve as experimental and potentially therapeutic targets to modulate NO bioactivity. There is tremendous promise behind NO itself as well as the numerous other molecules and processes associated with the L-arginine-NO-cGMP pathway. Collaborative efforts among bench scientists, clinical investigators and epidemiologists are the key in realizing this promise.

Historical review: Endothelin

Endothelin (ET) is a potent vasoconstrictive peptide that was isolated initially from the conditioned medium of cultured endothelial cells. In 1988, details of the isolation and identification, amino acid sequence, cDNA sequence and pharmacology of ET were published. Subsequently, ET isoforms, ET receptors and endothelin-converting enzyme (ECE) were cloned. Because ET was thought to be important in cardiovascular homeostasis, many investigators focused on the physiological and pathophysiological significance of ET. Accordingly, ET receptor antagonists and ECE inhibitors have been developed rapidly, mostly for the treatment of cardiovascular diseases. The field of molecular biology has provided valuable information about ET, including evidence that the ET system plays important roles in the early development of the neural crest and, thus, in the formation of organs. These results now present new avenues of ET research.

The pacemaker syndrome

The pacemaker syndrome is a complex of clinical signs and symptoms related to the adverse hemodynamic and electrophysiologic consequences of ventricular pacing in the absence of other causes. Neurologic symptoms or those suggesting low cardiac output or congestive heart failure, temporally related to the onset of ventricular pacing, are indicative of the pacemaker syndrome. The evolution of a clinically recognized syndrome, an analysis of possible mechanisms and clinical manifestations, and diagnostic approaches and their implications for management are discussed.

Cardiovascular disease resulting from a diet and lifestyle at odds with our Paleolithic genome: how to become a 21st-century hunter-gatherer

Our genetic make-up, shaped through millions of years of evolution, determines our nutritional and activity needs. Although the human genome has remained primarily unchanged since the agricultural revolution 10,000 years ago, our diet and lifestyle have become progressively more divergent from those of our ancient ancestors. Accumulating evidence suggests that this mismatch between our modern diet and lifestyle and our Paleolithic genome is playing a substantial role in the ongoing epidemics of obesity, hypertension, diabetes, and atherosclerotic cardiovascular disease. Until 500 generations ago, all humans consumed only wild and unprocessed food foraged and hunted from their environment. These circumstances provided a diet high in lean protein, polyunsaturated fats (especially omega-3 [omega-3] fatty acids), monounsaturated fats, fiber, vitamins, minerals, antioxidants, and other beneficial phytochemicals. Historical and anthropological studies show hunter-gatherers generally to be healthy, fit, and largely free of the degenerative cardiovascular diseases common in modern societies. This review outlines the essence of our hunter-gatherer genetic legacy and suggests practical steps to re-align our modern milieu with our ancient genome in an effort to improve cardiovascular health.

Cardiovascular disease from copper deficiency--a history

Although the nutritional essentiality of copper was established in 1928, a preoccupation with hematology delayed the discovery of cardiovascular disease from copper deficiency for more than a decade. Anatomical studies of several species of deficient animals revealed, interalia, aortic fissures and rupture, arterial foam cells and smooth muscle migration, cardiac enlargement and rupture, coronary artery thrombosis and myocardial infarction. Abnormal biochemistry in deficiency probably contributes to these lesions, e.g., decreased activities of lysyl oxidase and superoxide dismutase which result in failure of collagen and elastin crosslinking and impaired defense against free radicals. Copper deficiency also decreases copper in hearts and other organs and cells and increases cholesterol in plasma. Abnormal physiology from deficiency includes abnormal electrocardiograms, glucose intolerance and hypertension. People with ischemic heart disease have decreased cardiac and leucocyte copper and decreased activities of some copper-dependent enzymes. Copper depletion experiments with men and women have revealed abnormalities of lipid metabolism, blood pressure control, and electrocardiograms plus impaired glucose tolerance. The Western diet often is as low in copper as that proved insufficient for these people. Knowledge of nutritional history can be useful in addressing contemporary nutritional problems.

Developmental antecedents of cardiovascular disease: a historical perspective

Knowledge of the fetal antecedents of cardiovascular disease has increased rapidly since the association between low birth weight and the disease was demonstrated 20 yr ago. It now is known that individuals who had low birth weight or who were thin or short at birth are at increased risk for both cardiovascular disease and type 2 diabetes. This has been shown in studies in different countries and cannot be explained by confounding variables. Through clinical and animal studies, the biologic processes that underlie the epidemiologic associations and how their effects are modified by postnatal growth and by living conditions in childhood and adult life are beginning to be understood. One such process is altered renal development, with reduced nephron numbers, which may initiate hypertension.

From Belfast to Mayo and beyond: the use and future of plethysmography to study blood flow in human limbs

Venous occlusion plethysmography is a simple but elegant technique that has contributed to almost every major area of vascular biology in humans. The general principles of plethysmography were appreciated by the late 1800s, and the application of these principles to measure limb blood flow occurred in the early 1900s. Plethysmography has been instrumental in studying the role of the autonomic nervous system in regulating limb blood flow in humans and important in studying the vasodilator responses to exercise, reactive hyperemia, body heating, and mental stress. It has also been the technique of choice to study how human blood vessels respond to a variety of exogenously administered vasodilators and vasoconstrictors, especially those that act on various autonomic and adrenergic receptors. In recent years, plethysmography has been exploited to study the role of the vascular endothelium in health and disease. Venous occlusion plethysmography is likely to continue to play an important role as investigators seek to understand the physiological significance of newly identified vasoactive factors and how genetic polymorphisms affect the cardiovascular system in humans.

Therapeutic uses of inorganic nitrite and nitrate: from the past to the future

Potential carcinogenic effects, blue baby syndrome, and occasional intoxications caused by nitrite, as well as the suspected health risks related to fertilizer overuse, contributed to the negative image that inorganic nitrite and nitrate have had for decades. Recent experimental studies related to the molecular interaction between nitrite and heme proteins in blood and tissues, the potential role of nitrite in hypoxic vasodilatation, and an unexpected protective action of nitrite against ischemia/reperfusion injury, however, paint a different picture and have led to a renewed interest in the physiological and pharmacological properties of nitrite and nitrate. The range of effects reported suggests that these simple oxyanions of nitrogen have a much richer profile of biological actions than hitherto assumed, and several efforts are currently underway to investigate possible beneficial effects in the clinical arena. We provide here a brief historical account of the medical uses of nitrite and nitrate over the centuries that may serve as a basis for a careful reassessment of the health implications of their exposure and intake and may inform investigations into their therapeutic potential in the future.

A history of physical activity, cardiovascular health and longevity: the scientific contributions of Jeremy N Morris, DSc, DPH, FRCP

Since Hippocrates first advised us more than 2000 years ago that exercise-though not too much of it--was good for health, the epidemiology of physical activity has developed apace with the epidemiological method itself. It was only in the mid-20th century that Professor Jeremy N Morris and his associates used quantitative analyses, which dealt with possible selection and confounding biases, to show that vigorous exercise protects against coronary heart disease (CHD). They began by demonstrating an apparent protection against CHD enjoyed by active conductors compared with sedentary drivers of London double-decker buses. In addition, postmen seemed to be protected against CHD like conductors, as opposed to less active government workers. The Morris group pursued the matter further, adapting classical infectious disease epidemiology to the new problems of chronic, non-communicable diseases. Realizing that if physical exercise were to be shown to contribute to the prevention of CHD, it would have to be accomplished through study of leisure-time activities, presumably because of a lack of variability in intensities of physical work. Accordingly, they chose typical sedentary middle-management grade men for study, obtained 5-minute logs of their activities over a 2-day period, and followed them for non-fatal and fatal diseases. In a subsequent study, Morris et al. queried such executive-grade civil servants by detailed mail-back questionnaires on their health habits and health status. They then followed these men for chronic disease occurrence, as in the earlier survey. By 1973 they had distinguished between 'moderately vigorous' and 'vigorous' exercise. In both of these civil service surveys, they demonstrated strong associations between moderately vigorous or vigorous exercise and CHD occurrence, independent of other associations, in age classes 35-64 years. In the last 30 years, with modern-day computers, a large number of epidemiological studies have been conducted in both sexes, in different ethnic groups, in broad age classes, in a variety of social groups, and on most continents of the world. These studies have extended and amplified those of the Morris group, thereby helping to solidify the cause-and-effect evidence that exercise protects against heart disease and averts premature mortality.

Foundations for blockbuster drugs in federally sponsored research

'Blockbuster' drugs, which are widely prescribed and improve the health of millions, often originate in fundamental laboratory research. An important example of such drugs are the cholesterol-lowering drugs called 'statins', including Zocor, Pravachol, and Lipitor, which millions of people take in the U.S. every year. This short paper outlines the direct and indirect contributions of federally sponsored research to the development of these important drugs.

The Framingham Heart Study's impact on global risk assessment

Cardiovascular disease (CVD) is the leading cause of mortality, responsible for about 30% of deaths worldwide. Globally, 80% of total CVD deaths occur in developing countries. In recent years, age-adjusted CVD death has been cut in half in developed countries. Much of the decline is due to reductions in risk factors that the Framingham Heart Study helped to identify. The Framingham Heart Study also helped to classify those at highest risk by creating multivariate risk scores. As a result, other investigators have created various risk prediction scores for their countries. These scores have been the foundation for guidelines and prevention strategies in developed countries. However, most scores requiring blood tests may be difficult to implement in developing countries where limited resources for screening exist. New studies and risk scores inspired by the Framingham Heart Study need to simplify risk scoring in developing countries so that affordable prevention strategies can be implemented.

Trends in cardiometabolic risk factors in the Americas between 1980 and 2014: a pooled analysis of population-based surveys

BACKGROUND

Describing the prevalence and trends of cardiometabolic risk factors that are associated with non-communicable diseases (NCDs) is crucial for monitoring progress, planning prevention, and providing evidence to support policy efforts. We aimed to analyse the transition in body-mass index (BMI), obesity, blood pressure, raised blood pressure, and diabetes in the Americas, between 1980 and 2014.

METHODS

We did a pooled analysis of population-based studies with data on anthropometric measurements, biomarkers for diabetes, and blood pressure from adults aged 18 years or older. A Bayesian model was used to estimate trends in BMI, raised blood pressure (systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg), and diabetes (fasting plasma glucose ≥7·0 mmol/L, history of diabetes, or diabetes treatment) from 1980 to 2014, in 37 countries and six subregions of the Americas.

FINDINGS

389 population-based surveys from the Americas were available. Comparing prevalence estimates from 2014 with those of 1980, in the non-English speaking Caribbean subregion, the prevalence of obesity increased from 3·9% (95% CI 2·2-6·3) in 1980, to 18·6% (14·3-23·3) in 2014, in men; and from 12·2% (8·2-17·0) in 1980, to 30·5% (25·7-35·5) in 2014, in women. The English-speaking Caribbean subregion had the largest increase in the prevalence of diabetes, from 5·2% (2·1-10·4) in men and 6·4% (2·6-10·4) in women in 1980, to 11·1% (6·4-17·3) in men and 13·6% (8·2-21·0) in women in 2014). Conversely, the prevalence of raised blood pressure has decreased in all subregions; the largest decrease was found in North America from 27·6% (22·3-33·2) in men and 19·9% (15·8-24·4) in women in 1980, to 15·5% (11·1-20·9) in men and 10·7% (7·7-14·5) in women in 2014.

INTERPRETATION

Despite the generally high prevalence of cardiometabolic risk factors across the Americas, estimates also showed a high level of heterogeneity in the transition between countries. The increasing prevalence of obesity and diabetes observed over time requires appropriate measures to deal with these public health challenges. Our results support a diversification of health interventions across subregions and countries.

FUNDING

Wellcome Trust.

Trends in Cardiovascular Disease Mortality Among Persons With HIV in New York City, 2001-2012

BACKGROUND

Cardiovascular disease (CVD) has become more prominent among human immunodeficiency virus (HIV)-infected individuals. The extent to which CVD mortality rates are changing is unclear.

METHODS

We analyzed surveillance data for all persons aged ≥13 years with HIV infection between 2001 and 2012 reported to the New York City HIV Surveillance Registry. We examined age-specific and age-standardized mortality rates due to major CVDs. We compared mortality time trends among persons with HIV with the general population, and examined differences among HIV-infected persons by RNA level.

RESULTS

There were 29 588 deaths reported among 145 845 HIV-infected persons. Ten percent of deaths were attributed to CVD as the underlying cause, including chronic ischemic heart disease (42% of CVD deaths), hypertensive diseases (27%), and cerebrovascular diseases (10%). While proportionate mortality due to CVD among persons with HIV increased (6% in 2001 to 15% in 2012, P < .001), the CVD mortality rate decreased from 5.1 to 2.7 per 1000 person-years. After controlling for sex, race/ethnicity, borough of residence, and year, those with HIV had significantly higher CVD mortality than the general population in all age groups through age 65. The CVD mortality rate was highest among viremic persons (adjusted rate ratio [RR], 3.53 [95% confidence interval {CI}, 3.21-3.87]) but still elevated among virally suppressed (<400 copies/mL) persons (adjusted RR, 1.53 [95% CI, 1.41-1.66]) compared with the general population.

CONCLUSIONS

Our findings support continued emphasis by HIV care providers on both viremic control and preventive measures including smoking cessation, blood pressure control, and lipid management.

Uncovering the effects of smoking: historical perspective

Tobacco was introduced into Europe from America at the end of the fifteen century. At first used primarily for medicinal purposes it came to be burnt in pipes for pleasure on a large scale nearly 100 years later, at first in England and subsequently in Europe and throughout the world. Pipe smoking gave way to the use of tobacco as snuff and, in turn, to cigars and cigarettes at different times in different countries until cigarette smoking became the dominant form in most of the developed world between the two world wars. Societies were formed to discourage smoking at the beginning of the century in several countries, but they had little success except in Germany where they were officially supported by the government after the Nazis seized power. In retrospect it can now be seen that medical evidence of the harm done by smoking has been accumulating for 200 years, at first in relation to cancers of the lip and mouth, and then in relation to vascular disease and cancer of the lung. The evidence was generally ignored until five case-control studies relating smoking to the development of lung cancer were published in 1950. These stimulated much research, including the conduct of cohort studies, which, by the late 1950s, were beginning to show that smoking was associated with the development of many other diseases as well. The interpretation that smoking caused these various diseases was vigorously debated for some years but came to be generally accepted in respect of lung cancer by the late 1950s and of many other diseases in the subsequent two decades. Cigarette smoking has now been found to be positively associated with nearly 40 diseases or causes of death and to be negatively associated with eight or nine more. In some instances the positive associations are largely or wholly due to confounding, but the great majority have been shown to be causal in character. The few diseases negatively associated with smoking are for the most part rare or nonfatal and their impact on disease incidence and mortality as a result of smoking is less than 1% of the excess of other diseases that are caused by smoking. The most recent observations show that continued cigarette smoking throughout adult life doubles age-specific mortality rates, nearly trebling them in late middle age. All the diseases related to smoking that cause large numbers of deaths should now have been discovered, but further nonfatal diseases may remain to be revealed by cohort studies that are able to link individuals' morbidity data with their personal characteristics.

Challenges for research and prevention in relation to work and cardiovascular diseases

The purpose of this paper is to discuss future challenges for research and prevention in the field of work environment and cardiovascular diseases (CVD). First, research on CVD and work during the last half of the 20th century is discussed. Second, the theories dominating the last 20 years are presented. Third, cardiovascular and occupational epidemiology are compared, and it is stressed that occupational epidemiology should avoid the individualistic bias of mainstream cardiovascular epidemiology. Finally, future challenges are discussed, and improvements are recommended concerning the use of intermediate end points, intervention research, theories about chemical and physical risk factors, the use of a unifying model for society, stress, and health, and the application of integrated prevention. It is concluded that research on CVD and work can play an important part in the development of integrated prevention strategies for the next century.

The development of sex differences in cardiovascular disease mortality: a historical perspective

OBJECTIVES

Little is known about why males have higher cardiovascular disease (CVD) mortality rates than do females. An important factor that has hampered efforts in this regard is the lack of clarity about whether male excess mortality from CVD has existed throughout history. To answer this question, an investigation was conducted of trends in CVD mortality differences between the sexes from the time when data first became available until the present, including the full range of age groups.

METHODS

Mortality statistics for CVD in England and Wales from 1861 through 1992 and in the United States from 1900 through 1991 were used.

RESULTS

Three stages in the relationship between male and female CVD mortality were found: (1) An early stage of equal male and female mortality, (2) a stage of the appearance of sex differences in mortality, and (3) a stage with consistently present male excess mortality.

CONCLUSION

Male excess mortality from CVD has not always been present in the historical record. Further research is needed to elucidate the causes of this excess mortality.

Premature Mortality from Cardiovascular Disease in the Americas - Will the Goal of a Decline of "25% by 2025" be Met?

Background

Cardiovascular diseases (CVD) are the underlying cause 1.6 million deaths per year in the Americas, accounting for 30% of total mortality and 38% of by non-communicable deaths diseases (NCDs). A 25% reduction in premature mortality due four main NCDs was targeted by the 2011 High-level Meeting of the General Assembly on the Prevention and Control of NCDs. While overall CVD mortality fell in the Americas during the past decade, trends in premature CVD mortality during the same period have not been described, particularly in the countries of Latin America and the Caribbean.

Methods

This is a population-based trend-series study based on a total of 6,133,666 deaths to describe the trends and characteristics of premature mortality due to CVD and to estimates of the average annual percentage of change during the period 2000–2010 in the Americas.

Findings

Premature mortality due to CVD in the Americas fell by 21% in the period 2000–2010 with a -2.5% average annual rate of change in the last 5 year—a statistically significant reduction of mortality—. Mortality from ischemic diseases, declined by 25% - 24% among men and 26% among women. Cerebrovascular diseases declined by 27% -26% among men and 28% among women. Guyana, Trinidad and Tobago, the Dominican Republic, Bahamas, and Brazil had CVD premature mortality rates over 200 per 100,000 population, while the average for the Region was 132.7. US and Canada will meet the 25% reduction target before 2025. Mexico, Costa Rica, Venezuela, Dominican Republic, Panama, Guyana, and El Salvador did not significantly reduce premature mortality among men and Guyana, the Dominican Republic, and Panama did not achieve the required annual reduction in women.

Conclusions

Trends in premature mortality due to CVD observed in last decade in the Americas would indicate that if these trends continue, the Region as a whole and a majority of its countries will be able to reach the goal of a 25% relative reduction in premature mortality even before 2025.

History of right heart catheterization: 100 years of experimentation and methodology development

The development of right heart catheterization has provided the clinician the ability to diagnose patients with congenital and acquired right heart disease, and to monitor patients in the intensive care unit with significant cardiovascular illnesses. The development of bedside pulmonary artery catheterization has become a standard of care for the critically ill patient since its introduction into the intensive care unit almost 40 years ago. However, adoption of this procedure into the mainstream of clinical practice occurred without prior evaluation or demonstration of its clinical or cost-effectiveness. Moreover, current randomized, controlled trials provide little evidence in support of the clinical utility of pulmonary artery catheterization in the management of critically ill patients. Nevertheless, the right heart catheter is an important diagnostic tool to assist the clinician in the diagnosis of congenital heart disease and acquired right heart disease, and moreover, when catheter placement is proximal to the right auricle (atria), this catheter provides an important and safe route for administration of fluids, medications, and parenteral nutrition. The purpose of this manuscript is to review the development of right heart catheterization that led to the ability to conduct physiologic studies in cardiovascular dynamics in normal individuals and in patients with cardiovascular diseases, and to review current controversies of the extension of the right heart catheter, the pulmonary artery catheter.