Epidemiology testing hypothesis

Most scientists would hold that these unknowns and uncertainties in the regulatory risk-assessment model would tend to favor risk overestimation rather than underestimation or accurate prediction. While this view seems correct, it must be admitted that there is no epidemiological method available to test the hypothesis of an extra lifetime cancer risk of about 10 per 1000 000 from methylene chloride in drinking water. The same conclusion holds for most environmental carcinogens. It is also the case that more uncertainties attend the risk assessment process than we have indicated above. 

In contrast to the documented effect of cotton dust on acute responses, the causation of chronic respiratory effects in occupationally exposed subjects has not been established. The OSHA cotton dust standard is based on the premise that sustained exposure may result in chronic respiratory problems. To test this hypothesis, the pertinent literature is reviewed and discussed in an attempt to decide if convincing epidemiological documentation exists to support a cause and effect connection between prolonged dust exposure and chronic respiratory impairment. There appears to be a need for additional studies to clarify this important aspect of occupational medicine. 

The obj ective of epidemiological studies is to determine whether a causal relationship exists between a putative risk or protective factor and disease. Thus, most studies are designed to test a hypothesis Does exposure (e.g., consumption of cooked meats) cause disease (e.g., colon cancer) After the study is conducted, the data are analyzed and the magnitude of the putative association between exposure and disease is calculated. The study is then evaluated to see whether the association (if observed) could be a result of random or systematic errors or whether other exposures or factors are influencing the exposure of interest (i.e., effect modifiers). 

M.B. Schenker of Institute of Toxicology, University of California Davis in Davis, California is leading a multidisciplinary study supported by National Cancer Institute (NCI). This study will examine whether environmental asbestos deposits in California are associated with increased rates of mesothelioma. The study will address geological occurrence of asbestos and potential human exposure based on population patterns and known occupational exposure, and epidemiological characteristics of the disease in the state. The project will plan a case-control study to rigorously test the hypothesis that mesothelioma in California is independently associated with environmental asbestos exposure. 

Descriptive epidemiologic studies do not have a temporal component like case-control or cohort studies. Rather, this type of study evaluates factors that may influence the incidence of a disease, such as demographic or socioeconomic characteristics. It is not possible to determine causality from a descriptive epidemiologic study. Rather, this type of study is often used to generate a hypothesis that can be tested in case-control or cohort studies. 

The paradigm shift from qualitative observation to quantitative measurement is the cornerstone of science. This shift was advocated by Sir Francis Bacon in the 17th century who insisted that repeated observations of a phenomenon were the first step in a scientific methodology that included experimentation (Jardine 2011). The objective of an experiment might be to test a hypothesis, maximize or minimize a process operation, improve a formulation, reduce variability, compare options, etc. Experiments may be carefully controlled measurements in a laboratory in which extraneous factors are minimized or they may be observational studies of nature, such as an epidemiological study, or field studies. 

Meta-analysis is a detailed, cumulative analysis of data from several similar studies, which is usually based on scientific publications. One of its many advantages is that the assessment or testing of any hypothesis can be carried out on a much larger sample set than in any single tests. It is widely used both in chnical and epidemiological studies. 

Experimental study An epidemiological study designed to test a hypothesis about an outbreak of disease, often about the value of a particular treatment. 

Hope-Simpson, R. E. 1983. Recognition of historic influenza epidemics from parish burial records A test of prediction from a new hypothesis of influenzal epidemiology. J Hyg (Lond) 91 293-308. 

The present research used a cross-sectional observational epidemiological design and did not manipulate independent variables. For purposes of hypothesis testing the recruited subjects were assumed to be a random sample representative of children likely to be considered for screening for lead exposure in the EPSDT population. 

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