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作者 Yu, Winifred Wingyun
書名 The Application of Evidence-Based Methods to Nutrition Research and Challenges Encountered: Fiber and Cardiovascular Outcomes
國際標準書號 9781124889962
book jacket
說明 283 p
附註 Source: Dissertation Abstracts International, Volume: 72-12, Section: B, page: 7262
Adviser: Alice H. Lichtenstein
Thesis (Ph.D.)--Tufts University, Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy, 2011
The use of systematic review methodology to summarize all available data to answer a research question is increasing in the nutrition field. However, methodological issues unique to nutrition have not yet been adequately adjudicated. Research that focuses on factors influencing the validity and quality in conducting evidence-based review in nutrition is needed
The overall aim of this thesis research was to identify the challenges and to explore methods to facilitate the application of the evidence-based approach to nutrition research. Using the relationship of dietary fiber and cardiovascular clinical and risk factor outcomes as the test case, we qualitatively and quantitatively described the published literature by first developing an evidence map. An evidence map is a description of the type and amount of evidence in the literature for a particular research area. According to the evidence map, we found that the available literature was diverse. Two areas were identified where the available literature was judged adequate for conducing systematic reviews---(i) the association between dietary fiber types (total, cereal, vegetable, fruit, soluble, insoluble) and fiber-rich foods (whole grains, legumes), and the incidence and mortality of coronary heart disease (CHD) among observational studies, and (ii) the effect of oat, barley or beta-glucans supplement, and serum lipid concentrations or blood pressure among interventional studies. We found that evidence among observational studies for the association between dietary fiber and incidence and mortality of CHD was inconclusive. Among interventional studies, we found modest protective effects of oat, barley or beta-glucans supplementation on total and low-density lipoprotein cholesterol concentrations, but not for high-density lipoprotein cholesterol and triglyceride concentrations, and blood pressure
While conducting the above systematic reviews, we identified challenges when synthesizing dose data from epidemiological studies because of inconsistent reporting. This led to an exploration of different statistical techniques for conducting meta-analyses of epidemiological dose-response data, and comparison of statistical methods between (a) meta-analyses using only data from extreme exposure categories versus meta-analyses using data from all exposure categories, (b) meta-analyses using observed (crude, unadjusted) count data versus estimates obtained from adjusted data, and (c) meta-analyses using the 2-step approach, where study-specific effect sizes were first calculated and then combined across studies, versus the 1-step approach, where data from all primary studies are analyzed in one regression model. This comparison was done among 26 identified nutrition and health topics of meta-analyses. Compared to methods that uses all exposure categories, meta-analysis including extreme exposure categories only resulted in consistently greater magnitude of effects and wider confidence intervals. There was little difference in the results between meta-analyses using the 1-step approach versus the 2-step approach. Comparisons between meta-analysis using unadjusted data and adjusted data suggested no consistent pattern when discordant results were identified in the direction, statistical significance, or magnitude of effect
In summary, this thesis research identified the challenges encountered when applying the evidence-based approach to nutrition research and explored statistical methods for synthesizing dose-response data, using the relationship between dietary fiber and cardiovascular clinical and risk factor outcomes as a test case. Critical components of successfully conducting a systematic review for a nutrition topic include thoughtful research question refinement, rigorous protocol development, meticulous evaluation of the adequacy and types of available literature, and appropriate processing of the available data. When statistically synthesizing data from epidemiological studies, meta-analytic methods that consider the unique characteristics of dose-response data should be applied
School code: 1546
Host Item Dissertation Abstracts International 72-12B
主題 Health Sciences, Medicine and Surgery
Health Sciences, Nutrition
Health Sciences, Epidemiology
Alt Author Tufts University, Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy. Nutritional Epidemiology
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