BANOO PARPIA: Next let's move on to the study design and describe what was actually done in China to connect these data that provide this vast data resource and this historical database that has been analyzed, and will continue to be analyzed as we move on. One of the major research questions that was posed by the four principal investigators at the outset of the study was, how important is nutrition in the etiology of some of these diseases? More specifically, what role does nutrition play in disease causation for these chronic, degenerative diseases, such as cancer and heart disease?
The data from the first phase of the study was collected in 1983 using a multi-stage random sampling procedure. And by that, we mean first, the 65 counties of the units of analysis in the study were selected to obtain a wide geographic scatter-- that is, to ensure that we had one county in each of the provinces across the country-- and then to maximize the full range of seven of the most prevalent cancers. So once these counties were selected then, two communes were selected within each county randomly. A commune is what was referred to in 1983 and 1989. These units are referred to a xiangs, or villages. And within each of these communes, 25 males and 25 females, or 50 adults, between the ages of 35 and 64 years, were selected as the survey subjects.
So on these 6,500 individuals that were the survey subjects of the study, five general types of information were collected. First blood samples were collected, and biochemical indicators of nutritional status were analyzed. Urine samples were collected in males only after a load test of 5 milligrams of riboflavin and 500 milligrams of ascorbic acid. So vitamin C status and riboflavin status was assessed in the urine. Then we had a three-day food intake survey, dietary intake survey, which was conducted using a variety of food weighing and food disappearance techniques. This is essentially the gold standard to measure nutritional intakes.
In the West and in the US, we use 24 hour recall and food diaries and these kind of instruments to study dietary intake. But here in China, individual investigators went into the households, weighed the foods that were eaten, and then daily intakes of food nutrient intakes were estimated. After that, food samples were collected. So samples of the most commonly consumed cereals and vegetables were collected in their uncooked state and analyzed for fiber and other food constituents, including minerals and pesticide residues. And finally, a questionnaire was administered to get information on several demographic factors, but also on lifestyle factors such as smoking history, alcohol consumption, the frequency of consumption of certain foods, and the reproductive history in females.
In the follow-up study in 1989, there was an expanded and more robust study design. And let me just comment a little bit on the features of that study. The number of survey counties increased from 65 in 1983 to over 100 in 1989. Because in China we added four additional counties, which included some specific ethnic minority counties, which were very interesting in terms of their dietary intake habits. And then in Taiwan, there were 32 areas that were included in the study as well. So this increased the survey size enormously.
Several other surveys were conducted in 1989. There was an extended questionnaire that was given at different and multiple levels. So it was given not only to the household and the individual, but there was a questionnaire that was completed at the village level, at the xiang level, at the county level, and so on. So we had this nested set of socioeconomic data, which can be very effectively analyzed to look at context of dietary intakes and disease occurrence.
In addition, there was a survey that was conducted amongst all the mothers to babies born between 1986 and 1989 to determine the pregnancy, lactation, and child feeding practices in women. In addition, an anthropometric survey of children school-aged and ages three to four was done. So in other words, 300 children per xiang were selected to be weighed and measured for height. A survey on lung function was also conducted, as well as on blood pressure. So we have an expanded set of data in 1989.
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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 4 of 8 in the The China Project: Studying the Link Between Diet and Disease series.