epi exam 2
What is ethics with regards to human subjects protection
- Informed consent: Describes risks and benefits, purpose, how long it will last, procedures involved - Withholding treatment known to be effective: Being in a control group in an experimental design requires that medication be withheld from people who might benefit from it (one part of the term clinical equipoise) -Protecting the interests of the individual patient -Monitoring for toxicity and side effects -Deciding when to withdraw a patient from a study
How many people are covered in a census track?
4,000
Hawthorne effect
A change in a subject's behavior caused simply by the awareness of being studied
Disease registries such as SEER are good for what type of data
A disease registry is a centralized database for collecting data about a disease. Surveillance, Epidemiology, and End Results (SEER) Program - Conducted by the National Cancer Institute (NCI) Collects cancer data from different cancer registries across the U.S. Provides information about trends in cancer incidence, mortality, and survival
Difference between descriptive and analytic studies in terms of the hypothesis
A key feature of analytic studies is that they use comparison groups. In contrast to descriptive studies, which generate hypotheses, analytic studies are used to test hypotheses. They are used to look for and measure associations
Difference between prophylactic and therapeutic trial and examples
A prophylactic trial evaluates the effectiveness of a substance that is used to prevent disease; it can also involve a prevention program Example: Researchers from the London School of Hygiene and Tropical Medicine have achieved an astounding 86 per cent reduction in malarial infections in children under five during a study carried out in Senegal. Results published in The Lancet follow the randomised, placebo-controlled trial which took 1,136 children aged between two months and five years. Candidates were given intermittent doses of either the prophylactic combination of artesunate and pyrimethamine (Daraprim) or placebos Therapeutic usually denotes working with individuals who are ill Example: Twenty-three patients with rheumatoid arthritis on orthodox first-line anti-inflammatory treatment plus homeopathy were compared with a similar group of twenty-three patients on orthodox first-line treatment plus an inert preparation. There was a significant improvement in subjective pain, articular index, stiffness and grip strength in those patients receiving homoeopathic remedies whereas there was no significant change in the patients who received placebo. Two physicians were involved in prescribing for the patients and there were no significant differences in the results which they obtained. No side effects were observed with the homoeopathic remedies.
Examples of ecological studies
A study of mortality from lung disease in different cities that are known to have differing levels of air pollution would comprise an ecologic study. The unit of analysis is a city. Is the ranking of cities by air pollution levels associated with the ranking of cities by mortality from cardiovascular disease, adjusting for differences in age, percent of the population below poverty level, and occupational structure? Have seat belt laws made a difference in motor vehicle fatality rates? The question coud be addressed by comparing the motor vehicle fatality rates from years before and years after seat belt laws were passed Are daily variations in mortality in Boston related to daily variations in particle air pollution, adjusting for season of year and temperature? Are the long-term time trends (1950-1995) for mortality from the major cancers in the United States, Canada, and Mexico?
What is a cross sectional study?
A study that collects data at one point in time. Ex: surveys, data collected from individuals A type of prevalence study Exposure and disease measures obtained at the individual level Single period of observation (snap shot) Exposure and disease histories collected simultaneously Both probability and non-probability sampling used
Why do we have unplanned crossover designs
A treatment crossover is any change of treatment for a patient in a clinical trial involving a switch of study treatments. Unplanned crossovers exist for various unexpected reasons, such as patient's request to change treatment. For example, patients in a coronary bypass treatment may have misgivings about this invasive surgical procedure, or patients in a medical care group may require surgical treatment because of deterioration in their condition
Types of follow up
Active follow-up: The investigator, through direct contact with the cohort, must obtain data on subsequent incidence of the outcome. Accomplished through follow-up mailings, phone calls, written invitations to return to study sites/centers. Example: Minnesota Breast Cancer Family Study (mailed survey, reminder postcard, second survey, phone call to non-responders) Passive follow-up: Does not require direct contact with cohort members. Possible when databases containing the outcomes of interest are collected and maintained by organizations outside the investigative team. Example: Used in the Iowa Women's Health study
What is true about the US Census
Administered every 10 years Some segments of population is underrepresented Provides information about social-demographic characteristics
advantages and limitations of case-control studies
Advantages: Tend to use smaller sample sizes than surveys or prospective studies Quick and easy to complete Cost effective Useful for studies of rare or unusual diseases Limitations: Provide indirect estimate of risk Timing of exposure-disease relationship difficult to determine Representativeness of cases and controls often unknown
Crossover design advantages and disadvantages
Allows for a switch of study treatments All participants serve as both the control and treatment group. Treatment can be assessed for every participant. Disadvantages: carryover effect- a type of bias that may affect the results during the second period of the trial
Characteristics of a good study design
Allows you to compare two or more populations/groups Allows the comparison of risk of developing disease to be quantified (absolute or relative) Assess temporal sequence ( what came first the exposure or the outcome? Referred to as causality) Minimize biases, confounding, and error
This is one of the largest telephone survey conducted on risk behaviors that are linked to diseases (primarily chronic conditions)
BRFSS (behavioral risk factor surveillance system)
What are reportable disease statistics and limitations
By legal statute physicians and other healthcare providers are required by law to report cases of certain diseases known as reportable and notifiable diseases, to health authorities. These diseases are usually infectious and communicable ones that might endanger a population. Limitations include a possible incompleteness in population coverage. Not everyone that develops a disease will seek medical attention and some people may be asymptomatic therefore also never seeking medical attention. The may also be shortcomings or failures in physicians to report and fill out the paperwork.
Calculate an Odds Ratio and interpret the results
Calculate: (AD)/(BC) Interpret: OR = 1 implies no association Assuming statistical significance: ◦OR>1 greater odds of disease/injury/disability due to the exposure ◦OR<1 suggests a protective factor. Also interpreted less odds of disease/injury/disability due to the exposure OR = 2 suggests odds 2 x greater in getting disease based on the exposure
Note 3 limitations of mortality data
Certificate of cause of deaths (sometimes we get the cause wrong) Stigma of some diseases may lead to inaccurate reporting (if someone has personal relationship or agenda to keep a person's cause of death private to protect their reputation from stigma) Errors in coding or changes in coding
Characteristics of clinical trials and examples
Characteristics: A planned experiment Outcomes in treated group are compared with outcomes in an equivalent control group Same time period Focus is on the individual Types of clinical trials include medical interventions, prevention studies, diagnostic studies Examples: Medical Research Council Vitamin Study-- Tested for: role of folic acid in preventing neural tube defects Design: double blind Eligible subjects: women who were planning a pregnancy, had a previous child with NTD, and/or were not already taking vitamin supplements Esults: folic acid supplementation could now be recommended for all women who had a previously affected pregnancy. Public health: All women of childbearing age should receive adequate dietary folic acid. South Bronx, NY, STD Program-- Tested for: evaluated effectiveness of education efforts to prevent the spread of sexually transmitted diseases Subjects: African American and Hispanic male and female patients Results: increases in number of people practicing safer sex could have significant impact on public health Women's Health Initiative-- Tested for: elevated risk for breast cancer and CVDs after Hormone Replacement Therapy (HRT) Results: The clinical trial demonstrated that the epidemiologic findings on cancer were generally accurate, but the benefits on cardiovascular disease had been overestimated Use of HRT decreased 40-80% after the trial was stopped.
Strengths and Limitations of clinical trials and community trial
Clinical Trial Advantages: "Gold standard" for evaluating treatment/prevention intervention Investigator control Ability to demonstrate causality Randomization and blinding (if applied) eliminate biases (e.g. unknown confounding factors, experimenter bias) Clinical Trial Disadvantages: Time consuming Costly Allows to study 1 or 2 exposures/interventions to be tested Risk for treatment non-adherence or dropout Limited generalizability (limited applicability of findings to the larger community) Challenges ethics Address a narrow question Community trial advantages: Estimate realistically the impact of behavior change or other modifiable exposure in the incidence of disease Some types can be randomized Cluster randomized trial: trial that randomizes units such as communities to the conditions of an intervention. They randomize intact social units, such as households, primary care practices, hospital wards, classrooms, neighborhoods, and entire communities to differing intervention arms. Community trial disadvantages: Inferior to clinical trials with respect to ability to control entrance into study, delivery of the intervention, and monitoring of outcomes. Fewer study units are capable of being randomized, which affects comparability. Affected by population dynamics, secular trends, and nonintervention influences. Loss off effect may occur due to the shifting in the study population composition Secular trends with respect to prevalence of the exposure being modified make it difficult to determine the effect of the intervention Blinding and double blinding not generally used
Clinical trial phases and designs (know all the designs discussed in class and in your book
Clinical trial phases: Phase 1- test safety Phase 2- test efficacy Phase 3- confirm efficacy Phase 4- confirm efficacy for wider audience Two basic purposes: testing new medications (therapeutic trials) and substances to prevent disease (prophylactic trials) Clinical Trial Designs: Single-Blinded RCTs, Double-blinded RCTs, Unblinded RCTs, two-arm RCT, Cross-over RCT, Factorial RCT design, parallel RCT design Sequential design- investigators continuously monitor results and add subjects
advantages of the case-control studies ?
Cost effective Useful for studies of rare or unusual diseases Use smaller sample sizes than surveys or prospective studies Identifies possible causes of disease by finding out how the two groups differ with respect to exposure to some factor Quick and easy to complete
This refers to joining data from two or more sources e.g., employment records and mortality data
Data linkage or record linkage (same thing)
This is the primary limitation of insurance data
Data may not represent the entire population (not everyone has insurance)
Voluntary release of info by one investigator or inst to another for the purpose of scientific research
Data sharing
The nature of the data refers to the
Data source (e.g. vital statistics)
Exposure-based cohort studies
Definition: These studies overcome limitations of population-based cohort studies, which are not efficient for rare exposures. Certain groups, such as occupational groups, may have higher exposures than the general population to specific hazards. involve select subgroups w known exposures Sampling: select subgroups with known exposures Advantages: permit investigations of exposures that are uncommon Disadvantages: limited generalizability for public health inferences
Population-based cohort studies
Definition: exposures are unknown until the first period of observation when exposure information is collected. The cohort can then be divided into two or more exposure categories as a result of what is learned from the subjects. The nonexposed subjects become an internal comparison group Sampling: either an entire population or a representative sample of the population Advantages: results are generalizable, it is possible to define demographics and other characteristics of the parent population used in the research Disadvantages : exposures unknown until first information collection
amples of randomization (purpose, advantages, limitations)
Definition: the method of choice for assigning subjects to the treatment or control conditions of a clinical trial Purpose: subjects are stratified in order to improve comparability among conditions Advantages: limits bias, improves comparability Limitations: In order for randomization to be fully effective, a reasonably large number of subjects must be enrolled in order to obtain equal distributions of demographic and other variables in the study conditions. Examples: Two general methods for randomization: fixed and adaptive Fixed: easier to perform than adaptive; once subjects have been selected, pass eligibility, and agree to participate, they have an equal probability of being assigned to the intervention or control group. Simplest form of randomization is the "flip a coin" More elaborate protocols employ random numbers tables or computer algorithms. These are more typically used in clinical trials.
What data is on a death certificate
Descendants personal data, place of death, cause of death, physicians certification, funeral director/local registrar, spouse and parent information, usual resisdence
Limitations and strengths to the different types of studies
Ecologic: Strengths: Quick, simple, inexpensive Good approach for generating hypotheses when a disease is of unknown etiology Limitations: Ecological fallacy Imprecise measurement of exposure and disease Cross-sectional: Strengths: Can generate hypotheses Can estimate the magnitude and distribution of a health problem Limitations: Hard to detangle risk factors from factors associated with survivor Cannot study low prevalence diseases Cannot determine temporality of exposure and disease (or causation) Case-control study: Strengths: Tend to use smaller sample sizes than surveys or prospective studies Quick and easy to complete Cost effective Useful for studies of rare or unusual diseases Limitations: Provide indirect estimate of risk Timing of exposure-disease relationship difficult to determine Representativeness of cases and controls often unknown Cohort: Strengths: Permit direct determination of risk. Time sequencing of exposure and outcome. Can study multiple outcomes. Can study rare exposures Limitations: Takes a long time Costly Subjects lost to follow-up Experimental Strengths: Allows for manipulation Considered gold standard Investigator control Ability to demonstrate causality Allow randomization and blinding Disadvantages: Requires more time Costly Challenges ethics Only 1 or 2 exposures/interventions tested at a time Risk of non-adherence or dropout
Examples of case control studies
Examples: On the association between chili pepper consumption and gastric cancer risk: a case-control study conducted in Mexico City. Patients from the same hospital as a case The association between green tea consumption and lung cancer was the focus of a case-control study in Shanghai, People's Republic of China Birth defects research, heart disease research, infectious disease research also common examples (p.312)
Difference between quasi and experimental
Experimental has both manipulation and randomization. Quasi-experimental has manipulation but no randomization.
What is generalizability and another name for it
Generalizability (external validity) - ability to apply the findings of study to the population that did not participate in the study (the general population)
This act was signed in 1996 by former President Clinton to protect identifiable information
HIPPA
What are the DISADVANTAGES of Cross-sectional studies?
Hard to detangle risk factors from factors associated with survivor, Cannot study low prevalence diseases, Cannot determine temporality of exposure and disease or causation
What is HIPAA
Health Insurance Portability and Accountability Act of 1996 Sections of HIPAA "...require the Secretary of HHS to publicize standards for the electronic exchange, privacy and security of health information..." Categories of protected health information pertain to individually identifiable data
What are deficiencies in hospital data
Hospital data is often deficient for epidemiologic research applications because the individuals included do not represent any specific population.
Clinical trial history examples
In 1537, Ambroise Paré applied experimental treatment for battlefield wounds East India Shipping Company (1600) found that lemon juice protected against scurvy James Lind (1747) used the concurrently treated control group method
What are case control studies and characteristics
In a case-control study with two groups, one group has the disease of interest (cases) and a comparable group is free from the disease (controls) The case-control study identifies possible causes of disease by finding out how the two groups differ with respect to exposure to some factor Characteristics - A single point of observation (single point in time) Defined by presence or absence of the outcome Exposure is determined retrospectively Does not directly provide incidence data
High rates of follow-up are essential to the validity of cohort studies. What are some approaches that can be employed to ensure compliance when linkage to a central disease registry is not an option?
Mailings Medical evaluation phone calls written invitations to return to study sites/ centers Bio specimen collection Mailed survey Telephone technology answering machines/ caller identification
Know examples of community trials
Minnesota Heart Health Program Risk factors for atherosclerotic disease Stanford Five-City Project Designed to lower risk of cardiovascular diseases. Two treatment cities and two control cities were selected and randomly assigned to control or treatment. Pawtucket Heart Health Program Pawtucker was randomly selected for the intervention Focus of intervention was to help individuals adopt new, healthy behaviors and to create a supportive physical and behavioral environment, targeting risk factors, behavior change, and community activation Achieving cardiovascular risk reduction at the community level was feasible, but maintaining statistically significant differences between cities was not community Intervention Trial for Smoking Cessation (COMMIT) Multicenter project in 1989 Sought to reach cigarette smokers and bring about long term cessation of the habit 11 matched pairs of communities in US and Canada Project Respect RCT for prevention of HIV and other STDs. sought to establish the efficacy of several counseling methods for reducing high-risk sexual behaviors. Had 4 interventions. Results demonstrated that brief counseling sessions for risk reductions are effective in increasing condom use and preventing the occurrence of new STDs.
Statistics derived from Vital Registry System includes what
Mortality and birth (certificates from birth and fetal deaths as well)
2 strengths of mortality data:
Mortality data are nearly complete Useful for studying mortality overall and by specific cause
What is a multicenter trial
Multicenter trials--results from several researchers are pooled Recruitment of participants is extended across several to hundreds of accrual sites with data sent to a coordinating center for analysis They have been instrumental in the development of treatments for infectious diseases and recently in chronic diseases that are of noninfectious origin.
Absenteeism data is limited because
Not all people who are ill take time off Additionally, not everyone who says they are "sick" is actually sick
How study designs differ
Number of observations made Directionality of exposure Data collection methods Timing of data collection Unit of observation Availability of subjects
Examples of major cohort studies
Nurse's health study, Physicians health study, Framingham study
Know year of study, what disease they were looking for, and description of cohorts: Nurses study Physicians study Framingham heart study
Nurses study-- 1976, tested effect of contraceptive use on health outcomes such as CVD, smoking, and cancer. Cohorts were married, female RNs between 33 and 55 years old in 11 most populous states Physicians study-- 1982, testing effects of aspirin and beta-carotene on CVD and cancer. Cohorts were males ages 40 to 84 Framingham heart study-- 1948, tests various risk factors for CVD. cohorts were residents of framinghams, MA, ages 28-62 years old.
Odds Ratio vs Relative Risk - when does OR approximate RR?
OR ~ RR (Relative Risk) under 3 conditions: Disease is rare Controls are representative of target population Cases are representative of all cases
Difference between observational and experimental
Observational - no manipulation and no randomization. Experimental has both manipulation and randomization. Quasi-experimental has manipulation but no randomization.
Ecological fallacy
Observations made at the group level may not represent the exposure-disease relationship at the individual level. The ecologic fallacy occurs when incorrect inferences about the individual are made from group level data.
What is the best measure of association for case control studies?
Odds ratio
How do we determine the best controls
Perhaps the best way to ensure that the distribution of exposure among the controls is representative of the exposure levels in the population is to select population-based controls The use if population based controls is most likely to result in a control group that is representative of the exposure rate in the general or target population
Phases of trial and purpose of each phase
Phase I--tests a new vaccine in adult volunteers (fewer than 100 volunteers). Purpose: Is it safe? Phase II--expands testing to a group of 100 to 200 subjects (from the targeted population). Immunogenicity and reactogenicity in the target population are assessed, as well as antibody responses and clinical reactions to vaccines. Purpose: does it work? Phase III (the main test)--assesses the efficacy of the vaccine in the target population. Vaccine efficacy refers to the reduction in the incidence rate of a disease in a vaccinated population compared with an unvaccinated population. Assess protective efficacy in vaccines. Purpose: confirm efficacy. Phase IV - Tested for effectiveness in the general public. Continue to monitor efficacy and safety. Purpose: test for effectiveness in general public
Practical considerations in conducting a cohort study, also strengths and limitations
Practical Considerations: availability of exposure data, size and cost of the cohort, data collection and data management, follow-up issues, sufficiency of scientific justification Strengths: Permit direct determination of risk. Time sequencing of exposure and outcome. Can study multiple outcomes. Can study rare exposures Limitations: Takes a long time Costly Subjects lost to follow-up
Know the acts and laws related to protecting individuals information
Privacy Act of 1974 ◦Prohibits the release of confidential data without the consent of the individual Freedom of Information Act ◦Mandates the release of government information to the public, except for personal and medical files The Public Health Service Act ◦Protects confidentiality of information collected by some federal agencies
What is a retrospective versus a prospective study?
Prospective cohort study Definition: characterized by determination of exposure levels at baseline (the present) and follow-up for occurrence of disease at some time in the future Retrospective cohort study Definition: makes use of historical data to determine exposure level at some baseline in the past; "follow-up" for subsequent occurrences of disease between baseline and the present is performed
Be able to differentiate between the 3 types of cohort studies in terms of sampling, advantages and disadvantages
Prospective cohort study Definition: characterized by determination of exposure levels at baseline (the present) and follow-up for occurrence of disease at some time in the future Sampling: sampling strategy may be population-based or defined by a special exposure of interest Advantages: enable the investigator to collect data on exposures, the size of the cohort to be recruited is under greater control by the investigators than is the size of a retrospective cohort, biological and physical assays can be performed with decreased concern that the outcome will be affected by the underlying disease process, and direct measures of the environment can be made in order to define exposures precisely Disadvantages: investigators must wait for cases to accrue while conducting a prospective cohort study. Depending on the size of the cohort and the prevalence of a disease in the population, several years could elapse before meaningful analyses are feasible. Retrospective cohort study Definition: makes use of historical data to determine exposure level at some baseline in the past; "follow-up" for subsequent occurrences of disease between baseline and the present is performed Sampling: begin with exposure measured sometime in the past; the study subject is the entire cohort of exposed individuals Advantages: a significant amount of follow-up may be accrued in a relatively short period of time, and the amount of exposure data collected can be very extensive and can be available to the investigator at minimal cost Disadvantages: size of cohort to be recruited is under less control by the investigator than is the size of a prospective cohort Ambispective cohort study Definition: A design that makes use of both the retrospective (to determine baseline exposure) and prospective (to determine disease incidence in the future) features. Also known as historical prospective cohort study Sampling: cohort from those exposed to the exposure of interest, based on historical records Advantages: makes use of both prospective and retrospective cohort studies, can consider past exposures as well as study future exposures Disadvantages: follow-up may be difficult, very long time period
Which of the following are the DISADVANTAGES of Case-control studies?
Provide indirect estimate of risk Timing of exposure-disease relationship difficult to determine Representativeness of cases and controls often unknown
This act provides protection to certain agencies from releasing info when mandated by court order, etc.
Public Health Service Act
Which studies have higher validity
Ranked: Experimental study Controlled experiment/randomized clinical trial quasi-experiment/community trial Prospective cohort study Retrospective cohort study Nested case-control study Time series analysis Cross sectional study Ecologic study Case study Anecdote
Absentee data?
Records of absenteeism from work or school - useful for rapidly spreading conditions
What is validity
Refers to the ability to apply study findings to the intended audience
What is the best measure of association for Cohort studies?
Relative risk
What is relative risk and how do you calculate and interpret the results
Relative risk = Incidence rate in the exposed -------------------------------------- Incidence rate in the non-exposed Relative Risk - An estimate of the magnitude of an association between exposure and disease Interpretation: RR = 1 implies no association Assuming statistical significance: RR = 2 suggests risk 2 x greater of getting disease among exposed RR < 1 suggests a protective factor; exposure is associated with less risk of disease
This disease registry collects data about different cancers around the US
SEERS (surveillance, epidemiology, and end results program)
What have school health program data been used to study
School heath data provide information about immunizations, physical exams, and self-reports of illness
Single versus double masking
Single-blind design: subject unaware of group assignment. Researcher knows Double-blind design: Neither subject nor experimenter is aware of group assignment Purpose of blinding: maintain integrity of a study and reduce potential for bias
What is a census tract and how many residents are considered in the track
Small geographic subdivisions of cities, counties, and adjacent areas. Each tract contains about 4,000 residents.
What are sources of insurance data and limitations
Sources : ◦Social Security--provides data on disability benefits and Medicare ◦Health insurance--provides data on those who receive care through a prepaid medical program ◦Life insurance--provides information on causes of mortality; also provides results of physical examinations
What statistics are derived from vital statistics
Statistics derived from the vital registration system include mortality and birth certificates ( certificates from birth and fetal death)
Which of the following criterion state that factors inherent in the data may limit its usefulness
Strengths vs. limitations
What are strengthens and limitations of mortality data
Strengths- Mortality data are nearly complete. Useful for studying mortality overall and by specific cause Limitations - primary cause of death may not be clear. Death certificates list multiple causes of mortality as well as the underlying cause. Lack of standardization of diagnostic criteria employed by various physicians in different hospitals and settings. Stigma associated with some diseases Errors in coding by the nosologist Changes in coding
What is temporality
Temporality refers to the timing of information about cause and effect.
If I wanted info on characteristics of US population where would I go for data
The U.S. Bureau of the Census provides much information of value to epidemiologic research, for example, general, social, and economic characteristics of the U.S. population. - cited from the book.
What is the advantage of a cohort analysis
The benefit of cohort studies is that they allow us to measure risk (relative risk). This is Bc we have information about the timing between cause and effect (temporality)
What is a cohort effect and an example
The influence of membership in a particular cohort. Example: Tobacco use in the U.S.: Fewer than 5% of population smoked around the early 1900s. Smoking behavior is greatly influenced by the calendar year of birth
When are birth certificates unreliable
The mother might have inconsistencies and gaps in her recollection of events Certain malformations and illnesses that affect the neonate may not be detected at the time of birth.
Screening surveys and limitations
The term screening refers to the application of various tests and procedures in order to identify suspected cases of a disease. A screening survey is defined as an investigation of a particular group of persons in order to identify individuals who have unrecognized health conditions ( ex : infectious or chronic diseases). Limitations are that it would be difficult to generalize results obtained in any other setting than an epidemiologic one.
How do we decide the need for a cohort study in terms of scientific justification
There should be considerable scientific rationale for a cohort study This rationale should be grounded on prior research from various perspectives, such as study designs other than cohort studies, several different investigators, and several different study populations Additional justification for cohort studies may come from laboratory experiments or animal studies
In reference to the completeness of population coverage, the extent to which all cases of a health phenomenon have been identified refers to which term?
Thoroughness
Outcomes and clinical endpoints
To assess the results, investigators compare rates of disease, death, recovery, or other appropriate outcomes. The outcome of interest is measured in the intervention and control arms of the trial to evaluate efficacy.
The investigator's access to data is limited by the following factors
Use of protected health info without IRB approval or patient's permission Use of data with personal identifiable without IRB approval Use of zip codes from publicly available data without IRB approval
Uses of cross-sectional studies and limitations
Uses-Hypothesis generation, Intervention planning, and Estimation of the magnitude and distribution of a health problem Limitations -Hard to detangle risk factors from factors associated with survivor, Cannot study low prevalence diseases, Cannot determine temporality of exposure and disease (or causation)
Occurs at a single point of observation, defined by presence or absence of outcome, exposure determined retrospectively and does not directly provide incidence data
case-control
studies two groups, one group has the disease and is the cases and the other is the comparable group, which are the controls
case-control
study identifies possible causes of disease by finding out how the two groups differ with respect to exposure to some factor
case-control
ABSTRACT: "Self- reported injuries among left-handed and right- handed people were compared in a survey of 1,896 college students in British Columbia, Canada. Lefthanders were more likely to report having had an injury requiring medical attention during the last two years (OR=1.89, 95% CI 1.39, 2.58). The odds was highest for lefthanded males when driving motor vehicles (OR=2.35, 95% CI 1.25, 4.43). Regardless of handedness, males had slightly higher odds of injury than females."
case-control study
Questionnaires were mailed to every 10th person listed in the city telephone directory. Each person was asked to list age, sex, smoking habits, and respiratory symptoms during the preceding seven days. About 20% of the questionnaires were completed and returned. About 10% of respondents reported having upper respiratory symptoms
cross sectional
A prevalence study in which the exposure and disease measures are obtained at the individual level at a single period of observation
cross-sectional
This type of study can be used to generate hypotheses, intervention planning and estimation of a health issue's magnitude and distribution
cross-sectional
with this type of study, the exposure and disease are collected at the same time and used for probability and non-probability sampling
cross-sectional
ABSTRACT: "The authors examined the cross-national correlation of alcohol consumption (based on food availability data) and breast cancer in 20 developed countries. Weighted correlation coefficients for alcohol and breast cancer were 0.31 for mortality and 0.65 for incidence; the corresponding unweighted coefficients were 0.50 and 0.45. Correlation coefficients for fat consumption and breast cancer ranged from 0.69-0.89. After adjustment for fat consumption in multiple regression models, the positive alcohol-breast cancer association disappeared, while the fat-breast cancer correlation remained positive and strong. These findings do not support the positive alcohol-breast cancer association that has been suggested by analytical epidemiological studies. The multivariate results, however, should be interpreted with caution due to the potential variation in the extent to which national alcohol data reflect consumption among females."
ecologic
correlational studies (surveillance), unit of analysis is the group, not the individual
ecologic
Used when trying to establish a correlation between a rate of exposure and a rate of disease among groups or populations
ecological
fallacies can occur, which is when incorrect inferences about the individual are made from group level data:
ecological
What type of study is Framingham?
prospective Cohort study
ABSTRACT: In a classic study in the investigation of the health effects of cigarette smoking, volunteers working in 1,121 counties in 25 states in the U.S. recruited 447,196 men, age 33-92 and had them complete a questionnaire about their smoking habit. Five years later, 39,178 of these men had died, and it was concluded that life expectancy was diminished by cigarette smoking. Which of the following best describes the design of this study?
prospective cohort
What is unit of analysis in ecological study
the group
