Singapore Chinese Health
The Singapore Chinese Health Study was drawn from men and women, aged 45–74 years, who were permanent residents or citizens of Singapore and who resided in government-built housing estates; eighty-six percent of the Singapore population live in these facilities. The study was restricted to individuals who were members of the two major dialect groups of Chinese in Singapore: the Hokkiens and the Cantonese. Between April 1993 and December 1998, 63,257 individuals, approximately 85% of those eligible, were enrolled. Development of the cohort was funded by a grant from the National Cancer Institute.
Study participants completed a baseline in-person interview that took place in their home. The questionnaire elicited information on diet, demographics, current physical activity, reproductive history (women only), occupational exposure and medical history. At baseline, a 165-item quantitative food frequency questionnaire, developed for and validated in this population, along with color photographs to represent portion sizes, was used to assess usual diet over the past year. Beginning in 1999 the researchers added assessment of respiratory outcomes to the study by means of standardized questions on history of asthma, cough and phlegm production administered during a telephone interview. Interviews from the first wave of follow-up were completed in 2004. The second follow-up telephone interview cycle began in 2006.
The study team conducted and completed a questionnaire validation of self-reported incident asthma diagnoses. The large proportion of nonsmoking women in this study facilitates the study of other risk factors for respiratory disease. Findings from this study indicate a protective effect of dietary fiber from fruits and soy foods on the development of chronic bronchitis symptoms. In these data, fiber explains associations with antioxidant intake reported in studies that did not adjust for fiber. To better understand the complex interplay between correlated intakes of foods and nutrients, London studied dietary patterns in relation to chronic bronchitis symptoms. This work indicated that independent of fiber intake, high intake of a diet high in fresh and preserved red meat, refined carbohydrates, and sodium was associated with increased risk. This was the first examination of dietary patterns in relation to nonmalignant respiratory disease. The investigators also found that early life exposure to secondhand smoke was related to the development of chronic respiratory symptoms in adulthood among nonsmokers. This effect could be mitigated by adult intake of fiber. In the future, London’s work in the Singapore Study will focus on interactions between diet, environment and genetic susceptibility in relation to respiratory endpoints.
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Stephanie J. London, M.D., Dr.P.H. (http://www.niehs.nih.gov/research/atniehs/labs/lrb/gen-epi/index.cfm)
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