Web of causation

public health

1. Web of causation Presented by :Kumar Nyaupane

2. Introduction This model of disease causation was suggested by MacMahon and Pugh in their book “Epidemiologic principles and methods”. This model is ideally suited in the study of chronic disease , where the disease agent is often not known, but is outcome of interaction of multiple factors. The web of causation considers all the predisposing factors of any kind and their complex interaction with each other.

3. Contd … Above figure illustrates the complexities of a causal web of myocardial infraction. The basic theme of epidemiology is to study the clusters of causes and combinations of effects and how they relate with each other. It can be visualized that the causal web provides a model which shows a variety of possible intervention that could be taken which might reduce occurance of MI.

4. Prevention in web of causation The web of causation does not imply that the disease can not be controlled unless all the multiple causes or chains of causation or at least a number of them are appropriately controlled or removed. Sometimes removal or elimination of just only one link or chain may be sufficient to control disease.

5. Contd … In a multifactorial event therefore individual factors are by no means all of the equal weight. The relative importance of these factors may be expressed in terms of “relative risk”.

6. Contd.. Based on this theory it is believed that the prevention offers a better prospects for health than cure since, many of these factors can be modified. Since several factors contributes to several disease , community efforts were shifted to factors modification ( prevention) rather than disease treatment.

7. The prevention of myocardial infarction is based on some well designed strategies aimed at treating both asymptomatic high risk patient ( Primary prevention ) and patient with established CHD (secondary prevention). A positive impact from primary prevention can be basically achieved through a reduction in high blood pressure and by correcting dyslipidemia . The benefit can be increased by, Smoking cessation Increase physical exercise Reduction of body weight Moderate alcohol consumption.

8. Secondary prevention of MI can be obtained by, Controlling blood pressure. Reducing serum cholesterol in pt. surviving acute MI who can also benefit from administration of B-blockers , aspirin and ace-inhibitors.

9. Intervention at different level of prevention for MI Primordial prevention 1. Diet modification : diet rich in soluble fiber , vegetables, fruits and whole grains and low in saturated fat / trans fat and cholesterol should be encouraged. 2. Exercise 3. Low alcohol consumption 4. stop smoking

10. Primary prevention a. Health promotion . Healthy public policy - Taxes on energy dense foods - tobacco and alcohol control - Subsides for healthy food production . Health education - Effects of alcohol and smoking - Healthy food consumption - Low salt intake - Low fat intake - Daily exercise

11. b. Specific protection - blood [pressure - Lipid management - Weight management - Physical activity - High level of high density lipoprotein, Vitamin D , apolipoprotein B

12. B. Secondary prevention a. Diagnosis - Echocardiogram - Cardiac catheterization - Blood tests b. treatment - aspirin - thrombolytic therapy - heparin - Antiplatelet drugs - ace inhibitors - B- blockers

13. C. Tertiary prevention - Percutaneous coronary intervention and coronary artery bypass grafting. - cardiac rehabilitation program