Epidemiologic studies descriptive

There are two basic kinds of epidemiological studies, descriptive and analytical. The goal of the first is to describe the occurrence of disease in populations. Analytical studies identify and explain the cause of the disease. For instance, descriptive epidemiology may identify a new disease such as AIDS. Interpretation of descriptive results leads to analytical studies that examine the disease in more detail. Since epidemiology is the study of disease in populations, the proportion of affected individuals in a population is of basic importance. However, the epidemic pattern has varied from country to country. In the United States and the United Kingdom, 65% and 85%, respectively, of AIDS cases have... 

Respiratory Effects. Effusions and alveolar infiltrations of the lung occurred in a man who had washed his hair with an unknown amount of diesel fuel (Barrientos et al. 1977). Effects resulting from inhalation versus dermal exposure could not be distinguished in this case. An epidemiological study found a significant increase in feelings of "thoracic oppression" (no description provided) in workers who were chronically exposed to jet fuels by the inhalation, oral, and/or dermal exposure routes (Knave et al. 1978). The limitations of the study are discussed in detail in Section 2.2.1.2 under Respiratory Effects. 

Different methods are used in epidemiology. Epidemiological studies are often divided into descriptive studies and analytic studies. 

Experimental studies in laboratory rodents have demonstrated that a diverse array of chemical exposures suppress immune function (Table 19.2). In addition a limited number of clinical and epidemiologic studies have reported suppression of immune function and/or increased frequency of infectious and/or neoplastic disease following exposure of humans to some of these agents. From the description above it is clear there are a number of cellular and molecular targets for chemicals that act as immunosuppressants. Clearly, a chemical that disrupts cell proliferation would affect clonal expansion. Disruption of T cell maturation in the thymus is another potential mechanism for immune suppression. Chemicals may also interfere with receptor ligand binding at the cell... 

As explained in the detailed report (6), the above conclusions and recommendations were based on evidence from a data base consisting of descriptive as well as analytical epidemiological studies, and a vast number and variety of animal experiments and in-vitro tests. 

Wynder and Shigematsu (15) were the first to suggest that nutritional factors in general and specifically differences in fat intake may be responsible for the international variation in colon cancer incidence. Subsequent descriptive epidemiologic studies have found a strong positive association between colon cancer mortality or incidence in different countries and per capita availability in national diets of total fat (4,16) and of animal fat, estimated from food balance sheets. Such international correlations may be supportive of a hypothesis, but they should be interpreted with caution because the dietary data were based not on actual intake information but on food disappearance data. 

Circunstantial evidence directly implicating dopamine in the pathogenesis of duodenal ulcer in man is the unusual incidence of peptic ulcer disease in dopamine-deficient disorders. From purely descriptive clinical and epidemiologic studies we know that patients with Parkinson s disease, before the introduction of dopamine therapy, had an excess of ulcer disease (72). One report even comments on the curiosity that after initiation of L-DOPA administration the ulcer symptoms have virtually disappeared (72 ). On the other hand, less clearly, schizophrenia which is associated with dopamine excess and/or receptor hyperactivity is accompanied by virtual lack, or decreased prevalence, of peptic ulcer (73-76). Schizophrenia associated with ulcer disease has been viewed as a reportable curiosity in medical literature (75). At present, possibly because of the widespread therapeutic application of neuroleptics, the lack of peptic ulcer disease in schizophrenics is less striking than in the past. On the other hand, we recently observed in our autopsy series perforated duodenal ulcers in two schizophrenic patients who had been on large doses of haloperidol therapy (Szabo, unpublished observation). Thus, even in man, dopamine may indeed be implicated in the pathogenesis of duodenal ulcer disease. 

A brief description of known mechanisms of resistance to the drug and results of any in vitro studies regarding resistance or any known epidemiologic studies that demonstrate prevalence of resistance factors. 

Epidemiological studies can be categorized into three major types (1) descriptive or studies based on routine data, (2) analytical observational studies in which the researcher observes the occurrence of disease in two groups already segregated by disease or exposure, and (3) experimental studies in which the researcher randomly assigns individuals to the exposure in question. 

The analytical plan of epidemiological studies should use descrip tive and analytical techniques in describing the sample and results. Descriptive statistics, such as frequency distributions, cross-tabulations, measures of central tendency, and variation, can help explain underlying distributions of variables and direct the assessment of appropriateness of more advanced statistical techniques. Careful weighing of study findings with respect to the design and methods helps to ensure the validity of results. 

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.

There are several other types of descriptive epidemiology studies, but we need not say much more about them here. They will continue to be used to uncover major disease trends and to suggest hypotheses about cause-effect relationships. Full study of such hypotheses must be undertaken using more analytical techniques. 

The age of onset of a degenerative neurologic disease is 35, Epidemiologic study of affected persons indicates that most cases occur in the spring, are isolated (i.e., no neighbors or relatives are affected), and occur equally in men and women, Elowever, a subset of cases consists of two affected siblings in a family. The best description of this disease is... 

The types of epidemiologic studies used by risk assessors include case-control studies, cohort studies, descriptive epidemiologic studies, and case reports ... 

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. 

A description of studies used in assessing carcinogenic risk is given below. Epidemiological studies... 

The epidemiology of human disease caused by harmful marine phytoplankton is still at an early stage. This lack of progress in the phycotoxin disease epidemiology is attributed to a lack of disease biomarkers and exposure in humans. Epidemiology studies are limited to the mere description of clinically identified cases and little else. More recently, the studies have included laboratory testing of ingested food. 

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