Epidemiological studies statistical analyses

In most studies, phytoestrogen intake has been estimated by direct methods that evaluate food intake either by recall (food-frequency questionnaires -FFQs) or by record (food diary), and subsequently by composition databases based on information of this kind. Food-frequency questionnaires are widely administered to subjects involved in epidemiological studies. Their validity and reproducibility is considered sufficient when statistically correlated to data obtained from dietary records (a properly-completed and comprehensive food diary) and from analysis of blood and urine samples (Kirk et ah, 1999 Huang et al, 2000 Yamamoto et al, 2001 Verkasalo et al, 2001). FFQs can be repeated several times a year and may be administered to large populations. Such an approach provides an easy and low-cost method of assessing the... 

There is some USEPA precedent for use of statistical meta-analysis in a regulatory context, including the recent meta-analysis of organophosphate-related acetylcholinesterase inhibition data and meta-analysis of epidemiological studies on effects of 2nd hand tobacco smoke exposure. Warren-Hicks and Moore (1998) provide some discussion of the potential applicability of meta-analysis to ecological risk assessments. 

Kritchevsky and Kritchevsky (2000) provided a summary of the evidence linking dietary cholesterol to the risk of CHD in 10 cohorts from eight large, well-conducted prospective studies that were reported since 1980, which included the Nurses Health Study, the Health Professionals Followup Study and the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. In eight of the cohorts there was no statistical association between cholesterol intake and the risk of CHD. In one of the positive studies the association was established by simple univariate analysis and was not adjusted for other dietary variables. The other study adjusted only for fat intake. There is no compelling evidence from these epidemiological studies that dietary cholesterol is associated with the risk of CHD. 

Medicine and Pharmaceuticals. Applied mathematics, particularly the use of Fourier analysis and wavelet theory, has sparked explosive growth in the fields of medicine and pharmaceutical development. The enhanced analytical methods available to chemists and bioresearchers through NMR and Fourier transform infrared (FTIR) spectroscopy feciUtate the identification and investigation of new compounds that have potential pharmaceutical applications. In addition, advanced statistical methods, computer modeling, and epidemiological studies provide the foundation for unprecedented levels of research. 

The relation between oseltamivir and adverse behaviors was investigated in a large epidemiological study in Japan in the winter of 2006-2007 and the preliminary results were reported in Japanese oseltamivir had no adverse effects [256. However, the statistical analysis of the results has been criticized, and it has been suggested that a more appropriate analysis shows that the rate ratio of psychiatric adverse reactions to oseltamivir was 1.57 (95% Cl = 1.34, 1.83) [257. Two other studies have since been published. 

Because the epidemiological approach - or at least the statistical analysis that it involves - is theory-fi ee it is prone to many misinterpretations. This can best be illustrated with the findings of a recent study that evaluated the increased crash risk due to a specific color of a car. In other words, does the color of a car affect the likelihood of its getting involved in a crash Furness and his associates (2003) addressed that question by examining the data for 567 crash-involved vehicles in the Auckland region of New Zealand in which at least one of the occupants was either severely injured or killed. They compared the frequencies of different car colors in the crash sample to the frequencies of different car colors in an exposure sample of 588 vehicles traveling on the roads in the same region. The results of their analyses are summarized in Table 17-3. 

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