Epidemiology odds ratio

Again, in epidemiological studies or clinical trials there is nearly always a degree of uncertainty due to bias, chance and confounders. In these studies uncertainty is measured in terms of / -values, odd ratios, and relative risks, and so on. 

In humans, cases of hepatomas have appeared years after acute exposure to carbon tetrachloride, however, none of the cases could establish a causal link between the exposure and development of neoplasms." Epidemiological studies have also given inconclusive results. A cancer mortality study of a population of rubber workers reported a significantly elevated odds ratio relating carbon tetrachloride with lymphatic leukemia, and lymphosarcoma and reticulum cell carcinoma." A recent retrospective cohort mortality study of aircraft maintenance workers found an increased risk of... 

Epidemiological data can be analyzed in various ways to give measures of effect. The data can be represented as an odds ratio, which is the ratio of the risk of disease in an exposed group compared with a control group. Odds ratio can be calculated as... 

High-dose lead exposure is a recognized risk factor for stillbirth or spontaneous abortion. Epidemiologic studies of the impact of low-level lead exposure on reproductive outcome such as low birth weight, preterm delivery, or spontaneous abortion have yielded mixed results. However, a well-designed nested case-control study recently detected an odds ratio for spontaneous abortion of 1.8 (95% Cl 1.1-3.1) for every 5 / g/dL increase in maternal blood lead across an approximate range of 5-20 g/dL (Boija-Aburto et al, 1999). In males, blood lead concentrations in excess of 40 / g/dL have been associated with diminished or aberrant sperm production. 

After a study has been conducted, the data are analyzed to see whether an association is observed. This section briefly defines the two major measures of occurrence (incidence and prevalence) and discusses measures of associations in detail, focusing on the most common measures used in the epidemiological study designs described above, such as correlation coefficient, relative risk, and odds ratio. 

First, this chapter will describe a conceptual framework to illustrate the special challenges posed because exposures assessed for epidemiologic studies must be relevant to the health outcome under investigation. Secondly, some of the most commonly applied epidemiological study designs will be introduced, with special emphasis on exposnre assessment issnes associated with the design. Thirdly, some widely applied exposure assessment approaches will be introduced, ranging from qualitative classifications of exposure to quantitative exposure assessment of pesticide concentrations. The influence of measurement error on measures of association between exposure and disease, such as the slopes of exposure-response relationships and risk or odds ratios, will be briefly reviewed. Finally, exposure proxies used in case-control studies of chronic effects of pesticide exposure will be reviewed and the concepts introduced earlier will be applied. 

Stepping back to view the big pictun , one can see that the values for the risk ratio (3,0) and edds ratio (3.86), as calculated above, are not exactly the same. For both risk ratio and odds ratio, a value of 1.0 corresponds to a situation where no association exists betwHCcn the risk factor and the outcome. Fhe use of the risk ratio or odds ratio for expressing epidemiological data can be a matter of personal taste and custom. However, it should be noted that odds ratio has a valuable property not shared by risk ratio, as illustrated with imaginary data involving cholesterol and diabetes (Feinstein, 1985). 

Figure 1. Overview of epidemiological studies investigating the renal risk of analgesic consumption. A. Description of methodological details used in the included studies. B. Presentation of the overall risk (odds ratio with 95% confidence interval) associated to the consumption of any analgesic exceeding the mentioned dose. C. Presentation of the odds ratios with 95% confidence interval published in the included epidemiological studies focussing separately on the ingredients aspirin and paracetamol.

The odds ratio (OR) is commonly used in epidemiological and clinical studies to express the relationship between two populations [12,13]. It is defined as... 

A meta-analysis of 16 clinical studies showed a benefit of intensive blood glucose control in patients with type 1 diabetes as evidenced by a reduction in the frequency, severity, and a delay in the development or progression of diabetic comphcations including nephropathy. The Epidemiology of Diabetes Interventions and Complications study, which observed the DCCT subjects for an additional 4 years while they were receiving care from primary physicians, showed a continued benefit of IIT on the risk of nephropathy as defined by the development of microalbuminuria (53% odds ratio reduction in microalbuminuria). ... 

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