HED 343 Cohort Studies

HED 343 Cohort Studies - Cohort Studies Cohort a Also...

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Unformatted text preview: Cohort Studies Cohort a Also called • • • Prospective study Longitudinal study Follow-up study Cohort Studies Cohort a ascertain exposure levels for a group ascertain of people a then relate those exposures to the then subsequent development of disease or some other health outcome or Estimates of Exposures a usually free of many of the problems of measuring exposure that occur in cross-sectional or case-control studies • e.g., the health outcome influences the present level of the exposure or the recall of the past exposure Two Major Types Two a Concurrent • Also prospective cohort studies Also a Non-concurrent • Also retrospective cohort studies Concurrent Cohort Study a Follows a group of people forward through Follows forward real time real Example: The Framingham Study Example: The a The Framingham Study The Time: 1948 ~ 1950(selection), ~present 1948 a Place: Framingham, Massachusetts Framingham, a Person: 4469 men and women, aged 30-59 4469 a Selection: Random Random a Measurements: Personal characteristics ersonal such as diet, blood pressure, and overweight such a Outcome: Cardiovascular disease Cardiovascular a Non-Concurrent Cohort Study Non-Concurrent a Goes back in time, identifies the cohort from historic records, and traces the study subjects over time until the present subjects Example: Study about Reserpine and Example: Breast Cancer Study Breast a Reserpine and Breast Cancer Reserpine a a a a a Literature: Reserpine is positively related to the serpine occurrence of breast cancer occurrence Time: Early 1980's to track 1950~1973 Person: 2077 with breast cancer in 143,574 Place: Kaiser-Permanente HMO in San Francisco Measurements: Pharmacy records to identify Pharmacy who had received reserpine, women with breast cancer cancer a Reserpine is an indole alkaloid[2] antipsychotic and indole alkaloid antipsychotic antihypertensive drug known to irreversibly bind to storage antihypertensive vesicles of neurotransmitters such as dopamine, vesicles neurotransmitters dopamine norepinephrine, and serotonin.[3] Reserpine depletion of norepinephrine and serotonin monoamine neurotransmitters in the synapses is often used to bolster the theory that depletion of the neurotransmitters causes subsequent depression in depression humans. However a 1950's drug trial at Maudsley Hospital found that However in fact reserpine, far from causing depression, actually acted as an antidepressant. This has since been shown to be a function of dosage; low doses act as an antidepressant, while large doses cause monoamine depletion and depression. Moreover, reserpine has a peripheral action in many parts of the body, resulting in a preponderance of the cholinergic part of the nervous system (GI-Tract, smooth muscles vessels). a Quality of Data Quality a a Usually high for a cohort study because the disease generally does not influence the estimate of exposure of The number of disease (or outcome) events is The usually much smaller than in a case-control study. Thus, association estimates between exposure and a health outcome will usually be statistically unstable unless sample size is large unstable Advantages Advantages a Exposures are usually estimated years prior Exposures to the occurrence of disease to Thus, the disease state has a very low Thus, likelihood of influencing the estimates of exposure exposure a Disadvantages Disadvantages a Impractical and sometimes impossible Impractical for the study of rare diseases for Usually more expensive and timeconsuming than ecological, cross-sectional, consuming and case-control studies and a ...
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This note was uploaded on 04/12/2009 for the course HED 10520 taught by Professor Edmundson during the Spring '08 term at University of Texas.

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