Twelve-year results of the Coronary Risk Factor Study (CORIS).

BACKGROUND: After 4 years a coronary heart disease risk factor intervention programme produced equally large and significantly reduced risk profiles in two intervention towns compared with a control town. Intervention effects through community participation were assessed after cessation of the active intervention programme. The impact of secular trends was assessed in the control town and in two previously unstudied towns. METHODS: Cross-sectional surveys were done in a random sample of 1620 participants aged 15-64 years in the three original towns 12 years after the initial quasi-experimental study. Two years later 327 subjects, aged 35-44 years, were studied in the original control town and in two non-intervention towns. Risk factor knowledge, smoking and medical histories were determined by questionnaire. Blood pressure, anthropometry and blood lipids were recorded. Data were compared across towns, and with previous surveys. RESULTS: At 12 years the low intensity intervention town maintained a significantly better risk factor profile than the control town, while the high intensity intervention town now matched the control town. No differences in risk factor profiles were found between the control town and the two new towns. Deaths from coronary heart disease and strokes showed a downward trend in the study area. CONCLUSIONS: Outcome suggests large ongoing secular trends during the study could have overtaken the intervention effects in the high intensity town, but not in the low intensity intervention town, which showed an advantage over the control town. These results support the effectiveness of media-based, long term health promotion strategies to reduce cardiovascular disease risk profiles.

Community-based intervention: the Coronary Risk Factor Study (CORIS).

The Coronary Risk Factor Study (CORIS) examined the feasibility and effectiveness of a multifactorial community intervention programme to reduce coronary heart disease (CHD) risk factor levels. Three Afrikaner communities were surveyed before and after a 4-year intervention in two of the communities, the third serving as a control (C). Intervention was primarily by small mass media (low-intensity intervention, LII) or by small mass media plus interpersonal intervention to high-risk individuals (high-intensity intervention, HII). After allowing for change in C, significant net reductions in blood pressure, smoking, and risk score were obtained in LII and HII alike. Though the total cholesterol (TC) fell by 10-12%, there was no net reduction in favour of the intervention communities. However, LII and HII resulted in significant increases in high-density lipoprotein cholesterol (HDL-C) levels and HDL-C/TC ratios in comparison to C. Overall, the LII community fared almost as well as the HII community, and high-risk individuals did not show a greater change in risk factors than others. We conclude that community-based intervention works, and that in these particular communities a media-based health education programme was more cost-effective than one which adds a greater degree of interpersonal intervention.

Changes in smoking during a community-based cardiovascular disease intervention programme. The Coronary Risk Factor Study.

A prospective anti-smoking clinical trial was conducted as part of a coronary risk factor intervention study in three rural South African communities in the south-western Cape over a period of 4 years. The aim of this part of the study was to reduce smoking rates in two of the communities through application of high- and low-intensity intervention. The effect was evaluated by examining the net change in smoking habits, which was defined as the residual change in the intervention areas after allowing for change in the reference area. This paper presents the analyses of the estimated effect of the programme on the cohort aged 15-64 years at baseline who participated in the two surveys (4,087 subjects). The intervention programme among men in the high-intensity intervention area resulted in a reduction of 8.4% in smoking rates and 13.0% in the amount smoked per day. Among women in this area there was a reduction of 30.6% in smoking rates and 20.5% in amount smoked. Smoking and the amount smoked per day also decreased in the low-intensity intervention area, but less so than in the high-intensity intervention area. Smoking quit rates were strongly associated with initial smoking levels, with light smokers being significantly more successful quitters than heavy smokers. This study has proved that a community-based intervention programme can effectively reduce smoking.

Relation of family history and reversible risk factors to coronary heart disease prevalence in an Afrikaner community.

In a cross-sectional study of an Afrikaner community (n = 2,722 men and n = 3,173 women aged 25-64 years), family history of coronary heart disease (CHD) was associated with an adverse risk factor profile and with prevalent CHD. Men with myocardial infarction (MI) and a family history of CHD had higher total minus high density lipoprotein cholesterol (TC-HDLC) levels than men with MI but no CHD family history. In preliminary multiple regression analyses, family history of CHD appeared to exert its effect partly independently of known risk factors and partly dependently through age, TC minus HDLC, and HDLC. Even though their association with MI was weakened after entering family history into the models, the reversible risk factors (particularly TC minus HDLC, HDLC, and uric acid levels) continued to contribute to CHD. For MI in men, there was an interaction between family history of CHD and TC minus HDLC, to the extent that raised TC minus HDLC levels were adverse only in the presence of a positive CHD family history. The findings suggest coinheritance of high blood cholesterol and increased susceptibility to CHD. If confirmed in prospective studies, the interaction between family history and TC minus HDLC will have implications for cholesterol screening and management.

Choice of coronary heart disease risk factor variables in a cross-sectional study of white South Africans.

This report explores the possibility of redefining risk factors so as to improve their observed associations with prevalent coronary heart disease (CHD). A large cross-sectional community study of 5,895 white males and females aged 25-64 years yielded 240 cases of confirmed angina pectoris and 361 of confirmed myocardial infarction. Odds ratios for CHD end-points by level of risk factors when risk factors were expressed in the conventional manner (e.g. total cholesterol, systolic and diastolic blood pressure or current smoking) were often low and not statistically significant. Redefinition of risk factor variables in a manner that improved their specificity or compensated to some extent for the decreased risk factor exposure as a result of a CHD event (e.g. stopping smoking after a myocardial infarct) improved the strength of association. In this study, the most useful cholesterol variable was total cholesterol minus high-density lipoprotein cholesterol; for blood pressure the most useful variable was a blood pressure of 160/95 mmHg or above and/or being on anti-hypertensive treatment; and for smoking the most useful variable was the total duration of smoking (previous and current). Strong associations with CHD end-points were also found for conventionally expressed serum uric acid, diabetes prevalence (females) and family history of CHD. The study suggests that appropriate redefinition of risk factor variables and CHD end-points in cross-sectional studies yields associations similar in strength and direction to those found in prospective studies.

Socio-economic status, risk factors and coronary heart disease. The CORIS baseline study.

The relationship of socio-economic status (SES) indicators and coronary risk factors (RFs) with coronary heart disease (CHD) prevalence was examined in 5 620 subjects aged 20-60 years who participated in the Coronary Risk Factor (CORIS) baseline study. Education and income (with some exceptions in males) were strongly and inversely related to hypercholesterolaemia, low high-density lipoprotein cholesterol, hypertension, smoking, overweight and prevalence of angina pectoris. In contrast, type A behaviour was positively associated with higher income and education. Females showed stronger SES-RF relationships than males. Town-dwelling females were more likely to be smokers, and had a higher prevalence of angina pectoris and myocardial infarction. The lowest overall prevalence of RFs, angina pectoris and myocardial infarction was found in the professional and managerial categories for both males and females. The SES indicators had little or no independent effect on CHD prevalence in multivariate logistic analyses after inclusion of the standard RFs. We conclude that these indicators relate to RFs, and through them to CHD.

Smoking patterns in the coloured population of the Cape Peninsula (CRISIC study).

A cross-sectional study of tobacco-smoking habits in a random sample of 976 coloured subjects aged 15-64 years revealed that smoking was common, 57% of men and 41% of women being current smokers and 10.4% of men and 9.6% of women having stopped smoking. Heavy smoking prevailed, indicating by mean daily consumption of 14.2 and 13.1 cigarettes among male and female smokers respectively; only 33.5% of male and 39.6% of female smokers used less than 10 cigarettes per day. Coloured smokers smoked more heavily during the weekend. Both men and women smoked mostly filter cigarettes. Forty-four per cent of male and 49.5% of female smokers stated that they had attempted to stop smoking, mainly for health reasons. More than one-third of the participants had a positive attitude to combating smoking, particularly those with an educational level higher than Standard 7. Former smokers and heavy smokers had a significantly higher prevalence of ischaemic heart disease than the other participants. Smoking was associated with a low body mass index, low high-density lipoprotein cholesterol levels, low socio-economic standing, high alcohol consumption and type A coronary-prone behaviour in men. In 1982 the economically active coloured population of the Cape Peninsula spent an estimated R36.2 million on cigarettes.

Relationship between coronary-prone (type A) behaviour and other coronary risk factors in the coloured population of the Cape Peninsula.

In this investigation, conducted among 976 adult coloureds living in the Cape Peninsula, emphasis was placed on the relationship between type A (coronary-prone) behaviour and a number of other coronary risk factors (hypertension, hypercholesterolaemia, overweight and cigarette smoking), as well as certain demographic variables (age, occupational group and level of education). There was a fairly even distribution between high and low type A behaviour scores for both sexes in the groups aged 15 - 54 years, whereas there were proportionally fewer high than low scores in people between 55 and 64 years old. Housewives generally had lower scores than working women and other women who were not economically active. Both male and female respondents with high type A scores recorded on average higher systolic blood pressure readings. Type A men also smoked more than others. It appears that type A behaviour is mainly independent of other coronary risk factors.

Coronary risk factors in the coloured population of the Cape Peninsula.

A cross-sectional study of risk factors for coronary heart disease (CHD) in a random sample of 976 coloured people revealed a population greatly at risk of CHD. The major reversible risk factors--hypercholesterolaemia, hypertension and smoking--were very common, with 56% of the men and 40% of the women smoking, 18% of both men and women being hypertensive and 17% of both sexes being hypercholesterolaemic. At high cut-off points 62,8% of the men and 59,4% of the women had at least one major reversible risk factor. At lower but real levels of risk, over 80% of the population was affected. Other risk factors such as inactivity, overweight, hyperuricaemia, hypertriglyceridaemia and a positive family history of CHD were all common in this population group. A 'protective' high-density lipoprotein cholesterol level of greater than or equal to 20% of the total serum cholesterol level was found in 74,5% of the men and 81,1% of the women. A comparison with available data on other South African population risk profiles shows marked differences. The need for preventive strategies in the coloured population is clear.

Coronary risk factor screening in three rural communities. The CORIS baseline study.

A three-community study of rural Afrikaans-speaking Whites in the south-western Cape revealed that the major reversible risk factors hypercholesterolaemia, hypertension and smoking, as well as 'minor' factors such as inactivity, obesity, hyperuricaemia, coronary-prone behaviour and the irreversible risk factors of chest pain, ischaemic changes on the ECG and a family history of ischaemic heart disease (IHD), were exceedingly common. Singly or in combination, the major risk factors were present in the great majority of the study population after the age of 44 years. The interaction of high levels of lifestyle-induced risk factors with constitutional predisposition could adequately explain any excess risk of IHD in the Afrikaans-speaking community. The almost universal risk factor prevalence in this study has major implications for any preventive strategy.

[The control of hypertension in 2 communities. An interim evaluation]. / Die bekamping van hipertensie in twee gemeenskappe. 'n Interim-evaluasie.

More than 26% of Whites studied in two rural communities were found to be hypertensive during the 1979 Coronary Risk Factor Study (CORIS). At re-study during registration at the commencement of the hypertension intervention phase, hypertension could be confirmed in 72%. The mean blood pressures had decreased, and the percentages on treatment or with control of hypertension had improved by 43% and 136% respectively, indicating that screening for, and awareness of, hypertension had beneficial results. During the first 8 months of the hypertension intervention phase, 451 hypertensives were registered in the high-intensity intervention (HII) town, and 166 in the low-intensity intervention (LII) town. In both towns decreases in mean blood pressure and increases in treatment and control percentages could be demonstrated. In the HII town 80% of hypertensives were on treatment and 83% were controlled 4 - 8 months after registration, the most impressive results being achieved in the group which began treatment as a result of the intervention. A group with mild hypertension which was treated by non-pharmacological means only also improved, 66% eventually being controlled. The hypertension programme was three times more successful in the HII town, where the results suggest that hypertension in a community can be effectively controlled in the short term, using for the most part locally available health personnel and facilities.