Cardiovascular disease in the tropics. IV. Coronary heart disease

Worldwide Exposures to Cardiovascular Risk Factors and Associated Health Effects: Current Knowledge and Data Gaps

Information on exposure to, and health effects of, cardiovascular disease (CVD) risk factors is needed to develop effective strategies to prevent CVD events and deaths. Here, we provide an overview of the data and evidence on worldwide exposures to CVD risk factors and the associated health effects. Global comparative risk assessment studies have estimated that hundreds of thousands or millions of CVD deaths are attributable to established CVD risk factors (high blood pressure and serum cholesterol, smoking, and high blood glucose), high body mass index, harmful alcohol use, some dietary and environmental exposures, and physical inactivity. The established risk factors plus body mass index are collectively responsible for ≈9.7 million annual CVD deaths, with high blood pressure accounting for more CVD deaths than any other risk factor. Age-standardized CVD death rates attributable to established risk factors plus high body mass index are lowest in high-income countries, followed by Latin America and the Caribbean; they are highest in the region of central and eastern Europe and central Asia. However, estimates of the health effects of CVD risk factors are highly uncertain because there are insufficient population-based data on exposure to most CVD risk factors and because the magnitudes of their effects on CVDs in observational studies are likely to be biased. We identify directions for research and surveillance to better estimate the effects of CVD risk factors and policy options for reducing CVD burden by modifying preventable risk factors.

Secular growth and its harmful ramifications

Secular growth has been occurring in Europe for about 150 years. In the USA, since 1900, each new generation has increased by an average of 1in (2.54cm) in height and about 10lb (4.54kg) in weight. This trend has generally been viewed as favorable and tallness is admired, with the current ideal height for a man in the Western world being 6ft 2in (188cm). The Japanese have increased in height since the end of the Second World War by about 5in (12.7cm) in height and the Chinese have been growing at the rate of 2.54cm/decade since the 1950s. In spite of admiring greater height, a world population of increasing height and body-weight is a major threat to our environment, health and survival. Based on more than two decades of research, quantitative data are given for increased use of resources, and increased pollution, energy and fiscal costs resulting from a population of larger people. The laws of scaling are described to show why the impact of increasing stature has a non-linear impact on consumption, body-weight, strength, pollution and economic costs. Paleontological findings indicating that larger body size increases the risk of extinction are also discussed. Various studies indicate a loss of 0.47 year of longevity for each cm increment of height. Caloric restricted diets are also reviewed for their applicability to humans. Recommendations are made for dietary practices to moderate growth in our youth and to postpone development of chronic or degenerative diseases.

Some determinants of postprandial lipaemia in Nigerian diabetic and non-diabetic subjects

The efficiency of clearance of plasma triacylglycerols (TAG) after fatty meals in non-diabetic Caucasian subjects is believed to determine the plasma level of high-density-lipoproteins-cholesterol (HDL-C). It is unknown if this observation holds in diabetic subjects and in other racial groups. In assessing the factors that determine TAG responses to acute fat loading in a tropical African population with a low prevalence of atherosclerotic disease, twenty (nine obese) non-insulin-dependent diabetic (NIDDM) patients with optimal glycaemic control and twelve (six obese) age-matched non-diabetic subjects were given meals containing 50 g fat (in butter) and 75 g carbohydrate (in white bread) over 15 min in the morning after a 12 h overnight fast. The fasting plasma levels of glucose, TAG, total cholesterol (total-C), HDL-C, low-density-lipoprotein-cholesterol, insulin and glycosylated haemoglobin (HBAlc) were estimated; glucose and TAG levels were also measured postprandially for 8 h at 2 h intervals. Postprandial lipaemia was consistently higher in the diabetic patients (about 50-100% more than values obtained in the non-diabetic subjects, even when corrected for differences in body mass) and correlated positively with age and postprandial glycaemia. This defect in TAG clearance was even worse (by about 50%) when glucose tolerance became further impaired after ten of the diabetic patients stopped oral hypoglycaemic treatment for 1 week and the fat-tolerance test was repeated. In the obese non-diabetic subjects, but not those of normal weight, there were significant negative relationships between the postprandial lipaemia and fasting plasma levels of HDL-C and HDL-C: total-C ratio, as reported in Caucasians. It is concluded that age and the ambient glucose concentration appear to be the important determinants of the efficiency of TAG clearance in diabetic subjects. This accords with clinical observations of increased atherogenic liability with increasing age and poorer glycaemic control. The determinants in non-diabetic subjects were less defined, indicating that postprandial lipaemia might be influenced by various factors (obesity as shown here) in different subsets of individuals.

Hypertension studies in developing countries

Developing countries vary considerably with respect to the behaviour of the blood pressure among its populations. In many countries hypertension is the commonest cardiovascular disorder; but communities also exist within many of these countries that do not manifest hypertension. Some of the characteristics of such communities include primitive social structures and low dietary salt intake. Some special features of hypertension among African populations and persons of African descent may be related to fundamental differences in cellular handling of cations. Difficulties with hypertension control in developing countries are largely economic. The next decade should attempt to ascertain whether observed variations in hypertension prevalence might provide the key to the pathogenesis of high blood pressure and whether primary prevention might resolve the difficulties the developing world encounters in instituting hypertension control.

The unique merits of a low-fat diet for weight control

The virtual freedom from obesity enjoyed by many primitive societies may be traceable to the low fat content of their traditional diets. Recent studies indicate that humans have a very limited capacity for de novo lipogenesis from dietary carbohydrate; this implies that it should be easy to achieve negative fat balance if dietary fat intake is kept low and fat oxidation is promoted by regular exercise. Overfeeding with carbohydrate--but not with fat--provokes an insulin-mediated thermogenesis which acts to retard weight gain. Low-fat starchy foods have a relatively low caloric density, resulting in lower caloric consumption with meals. Once absorbed, carbohydrate has greater satiety value than fat. These considerations suggest that avoidance of dietary fat may be a more successful approach to weight control than "calorie counting". The efficacy of low-fat diets may be promoted by supplementary carnitine, which stimulates fat oxidation, and by chromium, which aids insulin-mediated thermogenesis. An unrefined low-fat diet, eaten to satiety and accompanied by regular exercise, may be the ideal means of maintaining a trim figure throughout life while minimizing one's risk for "Western" degenerative diseases.

Racial differences in platelet survival time in patients with symptomatic coronary atherosclerosis

Platelet survival times were studied in 40 patients (21 white and 19 black) with coronary artery disease and stable effort induced angina pectoris. The platelet survival times of 19 white controls (9.27 +/- 0.49 days; mean +/- SD) were not significantly different from those of 12 black controls (8.88 +/- 0.81 days), and the platelet survival times for 21 white patients with coronary artery disease (8.46 +/- 0.65 days) were lower than the times for both the white controls (p less than 0.01) and the combined control group (p less than 0.01). However, the difference between the mean platelet survival times of 19 black patients (9.22 +/- 0.68) and the control groups was not significant, and the difference between the mean platelet survival times of the 21 white patients and the 19 black patients was significant (p less than 0.01). Stepwise multiple linear regression analysis indicated that race was the most significant factor in predicting shortened platelet survival (r = 0.4783; p less than 0.01). It is concluded that racial background should be considered in the interpretation of platelet studies and that reported racial differences in the rate and extent of atherosclerotic lesions may be related to racial differences in platelet consumption.

Acute rheumatic fever in adults over the age of 45 years: an analysis of 23 patients together with a review of the literature

The natural history of acute rheumatic fever (ARF) in adults has been studied from an analysis of 23 patients together with a review of a further 466 published cases. In contrast to the picture in juvenile ARF, in our patients (average age 55 yr), only arthritis (83%) and carditis (35%) were major criteria for the diagnosis. All patients had at least 3 minor criteria. To summarize, 39% of the patients, average age 56 yr were seen in their initial attack of ARF. In those patients with a previous history of rheumatic fever, the mean interval between the index attack and the first illness was 20.5 yr. Contact with young children appeared to be an important predisposing factor. None had an ESR of less than 50 mm in the first hour, even in the presence of cardiac failure. Findings in the acute illness included anemia (70%), hyperglobulinemia (70%), urinary sediment (66%), and hypercalcemia in 7 out of 12 cases. The response to treatment was good and only 1 patient of 13 followed-up developed a new valvular lesion. A survey of the literature shows that attacks of ARF may occur at any age; death in the acute episode is rare and occurs only in patients with severe preexisting valvular disease with congestive failure. The problem of diagnosing active carditis in the presence of rheumatic heart disease (RHD) is discussed. While juvenile ARF may be overdiagnosed, the diagnosis may be missed in the adult rheumatic patient whose cardiac state inexplicably deteriorates. In such patients evidence for a preceding streptococcal infection should be sought. Patients with a high risk of developing ARF include those with carditis in previous attacks, with preexistent RHD, and with several children in the family. These factors should be considered when advising on the duration of antibiotic prophylaxis.

Milk, serum cholesterol, and the Maasai. A hypothesis

The Maasai of East Africa have been found to have low serum concentrations of cholesterol and a low incidence of cardiovascular disease in spite of apparently very high milk intakes. On that basis it has been frequently suggested that milk contains a "hypocholesterolaemic factor". The hypocholesterolaemia of the Maasai had also been attributed to a genetic adaptation. We feel that the milk intakes reported for the Maasai are excessively high and that the low incidence of cardiovascular diseases and low levels of serum cholesterol may be adequately explained by their variable and generally low energy intakes.

Serum cholesterol levels in a Nigerian population sample

Serum cholesterol was determined in 104 healthy Nigerians (57 males and 47 females). The average cholesterol concentration was 187 +/- 72.8 mg/100 ml (mean +/- SD) with a range of 60-480 mg/100 ml. Cholesterol levels were higher in males than in females and increased with age. Distribution of cholesterol level was generally skew to the left.

Serum cholesterol, triglycerides and heart disease of nomadic and sedentary tribesmen consuming isoenergetic diets of high and low fat content

1. The effects were examined of two approximately isoenergetic diets differing widely in saturated fat content on the levels of serum cholesterol and triglycerides of nomads and non-nomads in eastern Niger. Each person was also examined for clinical and electrocardiographic evidence of heart disease. 2. No significant differences could be found between serum cholesterol and triglyceride levels of 297 Anagamba nomad men consuming 73% energy as fat and 303 Kanouri sedentary men consuming 9% energy as fat. 3. Rheumatic heart disease was common in nomads and four possible cases of ischaemic heart disease were found in sedentary men only.