Epidemiology Midterm

Descriptive Research

(Surveillance) Research conducted to clarify the characteristics of certain phenomena to solve a particular problem.

How is health measured in the real world?

- Health Status (e.g. health conditions, human function and well-being, infant mortality, deaths) - Non-medical determinants of health (health behavior, living & working conditions, personal resources, environmental factors) etc.

Specificity - Validity

- Indicates how accurately the test identifies those without the condition or trait (i.e., the proportion of persons whom the test correctly identifies as negative for the disease [true negatives]) - High specificity is needed when re-screening is impractical and when reducing false positives is important. - The number of subjects who receive a negative test result and actually who do not have the disease, divided by all the subjects who do not have the disease. TN/(TN + FP) x 100%

Sensitivity

- Quantifies how accurately the test identifies those with the condition or trait and represents the proportion of persons with the disease whom the test correctly identifies as positive (true positives) - High sensitivity is needed when early treatment is crucial and when identification of all cases is important. - The number of subjects who receive a positive test result and who actually have the disease, divided by all the subjects who have the disease TP/(TP + FN) x 100%

Case-control studies

- Selection based on outcome/disease - Backward directionality (E<D) RETROSPECTIVE! - Study one disease, many exposures - Persons with rare disease of interest (cases) are compared to another group without the disease (controls) - Purpose: Do 2 groups differ in proportion of exposure to specific risk factors? - Measure: Odds Ratio (OR) •Advantages: •Inexpensive •First step in hypothesis testing •Good for rare conditions/chronic diseases •Can look for multiple risk factors/exposures •Disadvantages: •Past information may not be available or recall bias •Selection of control subjects may be difficult •Temporal relationship may be unclear

Screening

- The testing of groups of individuals who are at risk for a certain condition but do not manifest any symptoms, in order to determine the likelihood that these individuals will develop the disease - secondary prevention interventions.

Public Health Nursing

-Assessing the populations health needs -Diagnose and develop policy in relation to community health needs. -Plan for the community as a whole in order to prevent disease and disability and preserve the health of the community. For example, after an illness outbreak, the public health nurse will assess the need and develop a program for an immunization clinic.

Community Health Nursing

-Deliver health services to individuals, groups, and families -Diagnosis is based on the needs of individuals, family, or group.

To what degree do social determinants affect health outcomes?

-Socioeconomic factors (50%) -Health care (25%) -Genetics (15%) -Physical environment (10%)

Validity

-The accuracy of a test or measurement; how closely it measures what it claims to measure -In a screening test, validity is assessed in terms of sensitivity and specificity.

Measures of test accuracy

1) Reliability 2) Validity 3) Predictive value

Health promotion activities

1. Build healthy public policy 2. Create supportive environments 3. Strengthen community action 4. Reorient health services 5. Develop personal skills

Health Protection Activities

1. Communicable diseases 2. Protection from injury 3. Environmental health 4. Emergency health

Screening Criteria

1. Condition sought should be an important health problem. 2. Should be an accepted treatment for patients with recognized disease. 3. Facilities for diagnosis and treatment should be available. 4. Should be a recognizable latent or early symptomatic stage. 5. Should be a suitable test or examination. 6. Test should be acceptable to the population. 7. Natural history of the disease should be understood. 8. There should be an agreed policy on whom to treat as patients. 9. Cost of case-finding should be balanced with overall potential medical costs. 10. Case-finding should be a continuing process.

Stages of Surveillance

1. Data collection (Mandatory reporting of communicable disease, surveys) 2. Analysis & Interpretation (expert analysis of data) 3. Timely communication of findings (Disseminate knowledge)

5 health promotion action strategies

1. Develop personal skills (Stress management, healthy eating, exercise) 2. Create supportive environments (Support and empower ppl to maintain and enhance their health) --> Physical and social. ** churches, schools, workplaces 3. Re-orient health care services (Currently influenced by the biomedical model **Funding needs to be allocated to sustain health in the community) 4. Strengthen community action (Community development, Capacity building, Community mobilization, Empowerment) 5. Build healthy public policy (Positive effect on or promotes health, creating environments that support health and reduce inequities).

Scope of PHN

1. Health promotion 2. Prevention of illness 3. Health protection

Types of Screening

1. Mass: Involves total populations where prevalence is high 2. Selective: Applied to specific high risk groups 3. Multiphasic: Applying a variety of screening tests to one population, on same occasion 4.Case-finding: Testing to find specific cases

Illness Prevention Activities

1. Reproductive & family health 2. Sexual health 3. Prevention of chronic illness 4. Nutrition/food security 5. Mental health

Public Health

1. The health of a whole society. It can be measured and assessed through quantitative and qualitative indicators and analytic processes. 2. The specific policies, services, programs and other essential efforts agreed (ideally, and often, democratically), organized, structured, financed, monitored, and evaluated by society to collectively protect, promote, and restore the people's health and its determinants. 3. The institutions, public and private organizations—including private and public companies—, and other citizens organizations, that plan, develop, fund, and implement such efforts, and which are thus an integral part of local, national, regional, and global public health systems. 4. The scientific disciplines and professions, knowledge, methods, art, and craft essential to positively influence health determinants, and thus prevent disease and disability, prolong life, and promote health through the organized and collective efforts of society. Goals—diverse as they are in democratic societies—remain the same: to reduce the amount of health-related suffering, disease, disability, and premature death in the population.

Population Health

1. The health of the population measured by health status indicators; it is influenced by physical, biological, social, and economic factors in the environment, by personal health behavior, and by access to and effectiveness of health care services. 2. The prevailing or aspired level of health in the population of a specified country or region or in a defined subset of that population. The distinction between population health and public health is that population health describes the condition whereas public health includes the policies, programs, practices, procedures, institutions, and disciplines required to achieve the desired state of population health. The term also sometimes means the disciplines involved in studying the determinants and dynamics of a population's health status.

Passive surveillance

A form of surveillance where health care providers in the community report cases of notifiable disease. Long‐term, passive monitoring of general health trends and health determinants. Provides key info on the health status of a population.

Prevalance

A proportion of individuals in a population who have a particular condition at a particular point in time. - Prevalence increases with: -> Decreased mortality; -> improved life expectancy -> Increasing incidence of disease •Prevalence decreases with: -> recovery (cure) -> death •Existing cases •Status •Being, having •NB for measuring case‐ load Prevalence = Incidence x Duration P = I x D

Retrospective Study

A study that starts with the present condition of a cohort and collects data about their past history to explain their present condition.

Health Indicators

A variable, susceptible to direct measurement, that reflects the state of health of a population. Examples include infant mortality rates, incidence rates based on notified cases of disease, disability days, etc. These measurements may be used as components in the calculation of a health index

Predictive value

ABILITY OF TEST TO PREDICT THE PRESENCE OR ABSENCE OF DISEASE. - A third measure associated with sensitivity and specificity. - Positive predictive value - Negative predictive value

Prevention

Actions that prevent disease occurrence. Actions aimed at eradicating, eliminating, or minimizing the impact of disease and disability, or if none of these is feasible, retarding the progress of disease and disability. Levels of prevention, traditionally called primary, secondary, and tertiary prevention.

Standardized (Adjusted) Rates

Adjustment of rates so that meaningful comparisons of rates for important health outcomes between different geographic regions can be done

HAET Models

Agent, host and environmental interactions. - Agent: Can be excess or insufficient nutrition, poison, bacteria, smoke, viruses, trauma - Host: Immunocompromised, age, race, sex, customs, occupation, previous diseases - Environment: Physical such as weather, geography, pollution, housing, work

Primary prevention

Aims to reduce the incidence of disease by personal and communal efforts, such as decreasing environmental risks, enhancing nutritional status, immunizing against communicable diseases, or improving water supplies.

Secondary prevention

Aims to reduce the prevalence of disease by shortening its duration. If the disease has no cure, it may increase survival and quality of life; it will also increase the prevalence of the disease. It seldom prevents disease occurrence; it does so only when early detection of a precursor lesion leads to complete removal of all such lesions. It is a set of measures available to individuals and communities for the early detection and prompt intervention to control disease and minimize disability; e.g., by the use of screening programs. It is a core task of preventive medicine. Both early clinical detection and population-based screening usually aim at achieving secondary prevention. in certain diseases, these activities may also contribute to tertiary prevention.

Prospective Study

An approach to studying change over time that identifies research participants at the beginning of the project who are followed throughout the course of the research.

Experimental Study

Analytic studies: - Randomized control trials A study in which the researcher manipulates one of the variables and tries to determine how the manipulation influences other variables.

Observational Study

Analytic study Observational: - > Cross-sectional --> Longitudinal -----> Case-control -----> Cohort

Behavioral Prevention Strategies

Behavioral change models; teaching re: health promotion. Require individual action. (e.g. eating a healthy diet, exercise, smoking cessation)

Biological Gradient

Bradford Hill Criteria of Causation. (Dose-response relationship) •An INCREASE in the level, intensity, duration or total level of exposure to an agent leads to progressive INCREASE in risk. •E.g. smoking and lung cancer •If a threshold exists below which no further harm is done, further reduction in exposure is unwarranted Known fact. The association is coherent with firmly established knowledge on pathobiological processes. Exceptional caution is needed in this consideration: when the understanding of biological mechanisms is incomplete, implausible and speculative biological explanations will seem plausible and even coherent.

Temporality

Bradford Hill Criteria of Causation. - Exposure to the causal factor must PRECEDE the onset of disease. •Retrospective studies and Cross-sectional studies will also not beable to show temporarily. Exposure always precedes the outcome. This is the only necessary criterion of causality. Assessing the time order is not always straightforward (e.g., because of disease progression bias and other causes of reverse causation).

Analogy

Bradford Hill Criteria of Causation. - Implies a similarity between things that are otherwise different. ---> If one pharmaceutical drug (thalidomide) can cause birth defects, so might others. - Weaker criterion but is often a starting place for further research. Similar relations have previously been established. For example, if a virus has been found to cause a particular sarcoma in dogs, it might be reasoned that a similar virus causes the analogous sarcoma in humans. This consideration is not clearly distinguishable from plausibility unless the latter is limited to biology and analogy to upper (clinical, epidemiological) levels.

Strength of association

Bradford Hill Criteria of Causation. In general, the stronger the association between exposure and outcome, the more likely it is that the relationship is causal. This is defined by the size of the risk as measured by appropriate statistical estimates. The stronger, the more likely to be causal, although weak relationships may also be causal. Ratio! Percentage.. 2x

Consistency

Bradford Hill Criteria of Causation. Similar findings found in MULTIPLE studies. Consistency alone does not prove causation. The association is consistent when results are replicated in studies in different settings using different methods. Replicability and survivability.

Temporal relationship

Bradford Hill Criteria of Causation. if a factor is a cause of a disease, exposure must have occurred before the disease developed. Exposure always precedes the outcome. This is the only necessary criterion of causality. Assessing the time order is not always straightforward (e.g., because of disease progression bias and other causes of reverse causation).

Coherence

Bradford Hill Criteria of Causation. •Available evidence concerning the natural history, biology, and epidemiology of the disease must "stick together" (cohere) to form a cohesive whole. •Look @ BIG picture = makes sense?. ---> Multiple disciplines bring together the entire piece of the puzzle. The association is compatible with existing theory and knowledge. It may be theoretical and factual, biological, clinical, epidemiological, social, or statistical.

Experimentation

Bradford Hill Criteria of Causation. •Requires --> experimental studies --> natural experiments --> in vitro laboratory experiments, and animal models in support of a causal hypothesis. •Comparative medical research. An experiment shows that the caused condition can be altered (e.g., prevented) by changing exposure to the putative cause.

Plausibility

Bradford Hill Criteria of Causation. •The association needs to be plausible with known biological facts about the disease. --> Common sense and known biology must take precedence over statistical relationships. •Biological plausibility is also contingent on the biological knowledge of the day

Specificity

Bradford Hill Criteria of Causation. •causal factor should lead to only one disease and that the disease should result from only this single cause. Present when a putative cause produces a specific effect, as hypothesized or predicted by background theory (e.g., exogenous estrogen usage is expected to show a relation to hormone-sensitive conditions but not to seat-belt use). The particularity with which one variable predicts the occurrence of another. •When present is a very powerful criterion.

Primordial prevention

Conditions, actions, and measures that minimize hazards to health and that hence inhibit the emergence and establishment of processes and factors (environmental, economic, social, behavioral, cultural) known to increase the risk of disease. Primordial prevention is accomplished through many public and private healthy public policies and intersectoral action. It may be seen as a form of primary prevention

Florence Nightingale

Established sanitary nursing care units. Founder of modern nursing. began professional education of nursing.

John Snow & the Broad Street Pump

Fathers of modern epidemiology, in part because of his work in tracing the source of a cholera outbreak in Soho, London, in 1854. His findings inspired fundamental changes in the water and waste systems of London, which led to similar changes in other cities, and a significant improvement in general public health around the world.

Henle-Koch's Postulates

Four criteria for causative relationship between a microbe and a disease. Koch's postulates are the following: - The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms. - The microorganism must be isolated from a diseased organism and grown in pure culture. - The cultured microorganism should cause disease when introduced into a healthy organism. - The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

Louis Pasteur

French chemist and biologist whose discovery that fermentation is caused by microorganisms resulted in the process of pasteurization (1822-1895).

Population Health Promotion Model

Hamilton and Bhatti (1996) Combines: - 5 health promotion action strategies (Ottawa Charter for Health Promotion) - 12 determinants of health - Target populations (levels of action): ---> Individual, family, groups/aggregates, community, structures/systems, society -Evidence-based decision making

Environmental Prevention Strategies

Healthy public policy/laws, public protection. Those that society can impose and that require little effort on the part of an individual. e.g. laws limiting smoking, water supplies, seat belts

Cohort Studies

Incidence study. Quasi-experimental studies using two or more groups; epidemiologic designs in which subjects are selected based on their exposure to a determinant. A cohort study conducted by reconstructing data about persons at a time or times in the past. This method uses existing records about the health or other relevant aspects of a population as it was at some time in the past and determines the current (or subsequent) status of members of this population with respect to the condition of interest. Different levels of past exposure to risk factor(s) of interest must be identifiable for subsets of the population.

Rate

Information about Vital events that occur during a year's time, expressed as "rates". # of occurrences that take place during a year's time (numerator) / population at risk for the event (denominator).

Incidence

Measure of the rate of development of a given health condition in a population in a given time period. •Incidence increases with: -> Rise in development of disease (epidemics) -> Sudden, improved disease‐reporting procedures •Incidence decreases with: -> Resolution of epidemics -> Cure -> Excellent prevention measures •New cases •Change •Becoming •NB for establishing causation

Relative Risk

RR = [a/(a + b)] / [c/(c + d)] The ratio of the incidence of a health outcome (disease) among the exposed to that among the unexposed. The ratio of two risks, usually of exposed and not exposed. RR = 1 Risk is equal RR > 1 Risk is greater in exposed group RR < 1 Risk is less in exposed group

analytic epidemiology

Studies risk factors and the relationships among risk factors for the purpose of understanding the etiology of the disease or condition. "Why are certain groups at higher or lower risk of disease x than others?"

Lead Time Bias

Study error: Patients seem to live longer only because disease is detected earlier by test method than by conventional method. Earlier knowledge about the disease but the extension of life is no different than if you knew earlier or did not know earlier about the disease.

Morbidity rates

The amount of illness in a population. Useful in understanding the relative importance of a given illness or injury at a particular point in time / period of time.

Determinants of Health

The economic and social conditions that shape the health of individuals, communities, and jurisdictions as a whole.. Social determinants of health are about the quantity and quality of a variety of resources that a society make available to its members. 1.Income and social status 2.Social support networks 3.Education and literacy 4.Employment & working conditions 5.Physical environments 6.Social environments 7. Personal Health Practices and Coping skills 8. Healthy child development 9. Biology and genetic endowment 10. Health services 11. Gender 12. Culture

Robert Koch

The founder of modern bacteriology, he is known for his role in identifying the specific causative agents of tuberculosis, cholera, and anthrax and for giving experimental support for the concept of infectious disease --> Henle-Koch's Prostulates.

2x2 table

The most common way in epi to measure the association between an exposure factor and the occurrence of disease.

Screenable Population

The objective is to identify a high risk group: -Identifiable -Accessible -Accepting of the screening procedure -Be willing to seek treatment

Reliability

The precision of a measuring instrument, which depends on its consistency from one time of use to another, and its repeatability

Health Promotion

The process of enabling people to take control over those factors and conditions which influence their health. A collective, rather than individual activity.

Negative Predictive Value

The proportion of cases who truly do not have the disease among all those who received negative test results TN/(TN + FN) X 100 = _____% "How likely is it that one who tested negative actually does not have the disease?"

Positive Predictive Value

The proportion of cases who truly have the disease among all those who received positive test results TP/(TP + FP) X 100 = _____% "How likely is it that one who tested positive actually has the disease?"

Proportion

The relationship of one thing to another in size, amount, etc. # of people with attribute x # of people in the pop'n (can be expressed as a percentage, decimal)

Epidemiology

The study of the occurrence and distribution of health-related events, states, and processes in specified populations, including the study of the determinants influencing such processes, and the application of this knowledge to control relevant health problems.

Clinical Prevention Strategies

Traditional medical model for preventive health. Conveyed by a HCP to a pt, often within the clinical setting. (e.g. Vaccinations, screening and tx, monitoring)

Public Health Agency of Canada

a federal agency founded in 2004 to promote and protect the health and safety of Canadians with a focus on preventing chronic diseases and injuries, and responding to public health emergencies and infectious disease outbreaks. --> SARS outbreak = PHAC

Crude rate

a rate in which the denominator includes the total poplation

Case Control Studies

a type of retrospective study in which researchers begin with a group of people who already had the disease; studies that compare two groups: those who have a specific condition and those who do not have the condition. A detailed analysis of the occurrence, development, and outcome of a particular problem or innovation, often over a period of time. A detailed description of a concrete situation requiring ethical analysis, judgment, and—sometimes—action.

Tertiary prevention

measures aimed at softening the impact of long-term disease and disability by eliminating or reducing impairment, disability, and handicap; minimizing suffering; and maximizing potential years or useful life. It is mainly a task of rehabilitation

Randomized control trials

subjects randomly allocated to two or more groups (experimental or control), includes control group and experimental group = double blind. -> Most rigorous of the studies. -> Results observed at some future time (always prospective). -> Directional E>D

Analytical Research

tests hypotheses concerning the effects of specific factors of interest and allows causal associations to be determine. Observation of a disease to identify determinants of disease by showing relationship between disease and other factor.

Birth rate

the number of births in a year for every 1,000 people in a population.

Death rate

the number of deaths in a year for every 1,000 people in a population.

Active surveillance

when public health officials contact healthcare providers to ask about whether they are seeing particular types of disease or other means of collecting surveillance data. Active, ongoing, or short‐term surveillance. Searches for emergent diseases or outbreaks.

Cross-sectional studies

•Attempts to address question of strength of association btwn 2 factors (seeks to establish causation) •Info about D and E in a defined population collected at one point in time •Difficult to establish temporality (did E occur before D? no directionality established) •Multiple sampling strategies •Measure - prevalence

Exposure and Outcome

•Exposure (E) independent variable: •Risk factor, determinant, treatment, intervention •Outcome (D) dependent variable: •Health state, disease, death, survival, cure

Measures of Association

•Relative Risk (RR) or Odds Ratio (OR) •Depends on type of study •RR for cohort studies •OR for case-control studies •Either can be used for cross-sectional studies

Criteria for Causation

•Strength of association •Consistency •Specificity •Temporal relationship* •Plausibility •Biological gradient (dose-response) •Coherence •Experimental evidence •Analogy Bradford Hill (1965)

Cohort Study

•Tracks groups of individuals over time •Selection based on exposure(E) •Forward directionality (E->D) PROSPECTIVE!! •Study one exposure, many outcomes •Not suitable for studying rare disease •Prospective vs. retrospective cohort •Measure: Relative Risk (RR)