Epidemiology & Environment Terms in this set (62) Epidemiology the scientific study of the distribution & determinants of disease and the application of this study to protect public helath Environmental Epidemiology Provides... Specific information on wh

Epidemiology & Environment Terms in this set (62) Epidemiology the scientific study of the distribution & determinants of disease and the application of this study to protect public helath Environmental Epidemiology Provides... Specific information on whether environmental hazards impact human health risks In relations to environmental health, epidemiology... outlines methods to quantify health risks from exposure to chemical, physical, biological, or social factors What is the key approach of Epidemiology? To compare characteristics of the sick to the healthy Major Objective of Epidemiology/Human Research Studies To compare the occurrence or rates of disease or other health outcomes between groups known to be exposed at varying levels or not exposed at all Biomarkers Allows for identification of exposure or disease in early preliminary stages Model of Exposure & Body Diposition Source => a. Fate & Transport => Concentration => a. Exposure routes => Exposure => Absorbed dose=> Biologically effective dose => Possible health effect Who is the father of epidemiology? John Snow Mortality (death) - overall or specific causes of death Morbidity (non-fatal outcomes) - Studying a diseased (morbid) state Prevalence Proportion of population with existing disease at a given time Incidence New cases of disease during given time period ; (Only newly diagnosed cases are counted & is the preferred metric when identifying the trigger/risk factors for a disease) Disability-Adjusted Life Year Characterizes not only the association between risk factors and disease but also the impact factors have upon quality of life 1 DALY =? The loss of one year of productive life Prevalence Equation # of existing cases/ # in population who could be cases Incidence proportion (also known as Risk) (new cases/# people at risk ) over a specified time period Descriptive Epidemiology Describes patterns of disease in populations by person, place, or time (No particular hypothesis, just reporting) Case series Noteworthy set of cases Ecological fallacy The bias that may occur because an association observed between variables on an aggregate level does not necessarily represent the association that exists at an individual level Surveillance Tracks and compares disease rates across places, diseases, and time Surveillance biomonitoring use of biomonitoring to document rates of exposure or disease in populations Crude Rates Use actual observed disease numbers Crude rates are... for different population, of for the same population at different times, are not comparable Crude rates...cont'd - Not comparable when characteristics of the population change over time - Crude rates may obscure differences in disease occurrence by group Adjusted rates Use specific or standardized rates - Age-adjusted Ecological study An epidemiologic study that uses group-level data instead of data from individual participants (data may be easier to easier to obtain) Ecological study cont'd Adjusted mortality or morbidity rates for a disease are compared between different populations Benefits of Ecological Study - Use available data, so study may be quicker to analyze - Cost effective - Can help to generate hypotheses Disadvantages of Ecological Study - Trends occurring in group-level data may not be true at the individual level - Ecological fallacy Observational Analytic Epidemiology Goal: To test a priori hypotheses regarding an exposure with a specific outcome of interest Cross-sectional studies primarily prevalence surveys Benefit of Cross-sectional studies Snapshot in time: Exposure and disease at the same time Limitation of Cross-sectional Studies Temporality: did exposure precede the disease? Cohort Studies Identify participants based on their exposure status, follow through time, then determine and compare incidence rates between exposure groups Cohort Studies cont'd - can be done prospectively or retrospectively - Relative Risk (RR) ratio - Relative risk greater than 1 indicates and exposure to be harmful Case-control studies identify those with and without the disease in a population and compare their past exposure - Uses Odds Ratio Odds Ratio (OR) Quantifies the degree of association between exposure rates for cases and controls - OR serves as an appropriate surrogate for the RR Relative Risk (RR) Prevalence of Disease in Exposed Group/ Prevalence of Disease in Nonexposed Group Relative Risk A ratio that quantifies the strength of association between exposure and disease Relative Risk >1 (greater than 1) indicates exposure may be harmful RR < 1 Disease prevalence is less common in exposure group compared with non-exposed group RR=1 Considered "null" - no association Prevalence of Disease in Nonexposed Group Number with Disease in Nonexposed Group/ Total Number in Nonexposed Group Case-control Studies determine past exposure for all study subjects Case-Control Study Recruit... participants into a study based on their disease status (As a case with the disease or one free of the disease being studied) OR equation Odds that a Case was Exposed/ Odds that a Control was Exposed Odds that a Case was Exposed # of Cases in Exposed Group/ # of Cases in Nonexposed Group Odds that a Control was Exposed # of Controls in Exposed Group/ # of Controls in Nonexposed Group OR = 1 "Null" - No association or that the odds of exposure among cases and controls is the same OR > 1 Exposure is associated with higher odds of disease OR < 1 Exposures is associated with lower odds of disease Cohorts Used for common exposures (prospective cohorts) or rarer occupational exposures (if access to employment records exist to conduct retrospective cohort Case-control studies useful for assessing risk factors for rare diseases (Participants recruited based on disease status) Experimental studies... such as clinical trials, are not typically appropriate for environmental health hypotheses; Except for community trials such as study of fluoride in drinking water and the development of dental cavities When evaluating epidemiologic associations they must be assessed for internal and external validity Internal Validity Assessment determines if the association might be due to random chance, a systematic error during the conduct f the study (bias), or influence of a third variable that confound the observed association Challenges of Evaluating Epidemiologic Associations? - Long latency periods - Exposure to multiple harmful exposures - Modest relative risk Informed Consent musts tell enrolling individual about.. - What the study is about What will be collected form them - Inform of potential risks/benefits of participating - That they can withdraw at any time Causality Whether a causal connection has been shown, as opposed to merely a valid and statistically significant association Factors researchers consider when judging Causality.... - Strength of Association - Consistency across studies - Temporal relationship (exposure precedes disease) - Dose-response relationship (Risk increase with increasing exposure) - Biological Plausibility