BANOO PARPIA: So the initial data that constituted the core of the project, the 1983 data, were connected at a time when China was undergoing the epidemiologic transition. And by epidemiologic transition we mean a time in the country's history when the disease profile shifts or transitions from the infectious communicable diseases to the more chronic degenerative diseases, such as cancer and heart disease. And the study provides an extraordinary snapshot of China at this particular point in time.
It is important to note that this decline in the infectious diseases in the West was not due to modern medical practices and curative measures, such as the pharmaceuticals and vaccines and so on. But it was essentially due to prevention. If we look at the slides here that are on the screen on the right, we see the decline of diseases such as pneumonia, influenza, diphtheria, and so on, coming down way before the modern medicines were discovered or introduced.
Look, for example, at penicillin. It was discovered in 1930, and this was way after scarlet fever and tuberculosis actually declined. So it was essentially through sanitation-- improved sanitation measures, better public hygiene, and better nutrition. In fact, by some estimates better nutrition accounts for 75% of this decline.
So it is in this context then that we should be viewing the chronic degenerative diseases where nutrition has a large role to play. The decline of diseases could be really primarily through prevention before some of these genetic so-called modern miracle drugs or treatments could perhaps come about. We have an extraordinary opportunity to in fact utilize prevention with nutrition at its core to bring about the decline of these diseases.
The project is an epidemiologic study. And as we know, epidemiology is the study of disease causation. And epidemiologists study how human health is affected by our relationship to the total environment. And by the environment, we mean not only the physical environment, the air, the water, the soil, and so on, but also the nutritional environment, the social and economic environment, and so on.
So environment is defined in the broadest possible sense here. There are several types of epidemiologic studies, case control studies, cohort studies, prospective studies, randomized clinical trials, and so on. I won't go into defining each one of these studies.
But I will say that the China project is one specific type of epidemiologic study known as an ecologic study, or sometimes referred to as a correlational study. An ecologic study is one in which the unit of analysis is the population or an aggregate of individuals and not simply an individual. So we study populations and not individuals.
An ecologic study also looks at the degree of association between a specific risk factor or exposure and an outcome or a disease. Now, I'd just like to say a word or two about what a correlation coefficient is, especially for those of you who may want to pursue this a little further and open the monograph and take a look at the relationship between a specific exposure or risk factor and a specific disease. Because the correlation coefficient is the measure, the statistical measure of the degree of association between these two factors.
A correlation coefficient is simply a number that ranges from 0 to 1. The higher the value of the number, the stronger the degree of association. So 0.99 would be a very, very strong association between risk factor and a disease.
The number can also be positive or negative. And that direction essentially tells you whether in fact the association is positive or negative. For example, cholesterol is positively associated with heart disease. So that's a positive correlation coefficient.
A negative correlation coefficient would be the number of green vegetables, let's say, that is eaten and heart disease risk. So the greater the amount of green vegetable intake, the lower the degree of heart disease-- the lower the risk of heart disease. Another criteria that is used to assess the correlation coefficient is the degree of statistical significance, typically referred to by stars by the side of the number in the monograph. And this statistical significance is the degree of confidence that we have that the association didn't occur by chance alone.
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This study room provides a general overview and introduction to the Cornell-China-Oxford project. The project is a large and comprehensive epidemiologic study designed to explore and investigate the relationship between diet and disease.
In addition to the general descriptive findings of the study, the implications of this body of research evidence for prevention of chronic diseases such as heart disease and cancer are discussed.
This video is part 2 of 8 in the The China Project: Studying the Link Between Diet and Disease series.