Study Guide

Study Guide

Review questions 1

Long-term and short-term fluctuations show the pattern of disease occurrences by its distribution by time. Short-term variation of a disease is the occurrence of an illness or other health-related conditions in a region or community more than the average expectancy. Types of short-term changes include common source epidemics, propagated epidemics, and slow epidemics. An example of shorter fluctuating disease is leptospirosis cases in an area that affect swimmers who swim in an infected rehabilitation lake. Long-term/ temporal fluctuation in a condition refers to the progressive increase or decrease in a disease for several decades or years (Rosmalen et al. 18). An example is an increase in cases of lung cancer, coronary heart disease, and diabetes or the decrease in polio, typhoid and tuberculosis cases.

Uses of epidemiology

1. a) Epidemiology can be used in historical studies of the health in a community and the increase or decrease of diseases within the population. This history can be used to make projections into the future of any possible outbreaks or occurrences.
2. b) It can be used in community diagnosis of the nature, distribution, and presence of health and diseases among the population.
3. c) Can also be used to assess the progress of health services which begins by determination of the needs and healthcare resources available. These studies or assessments can be compared between different populations.
4. d) Epidemiology can be used to determine own chances and risk factors of the disease.
5. c) Epidemiology helps in coming up with a complete picture by including all cases in proportion and relating all clinical disease by observing their secular changes and similar from other places.
6. e) It also helps in the identification of syndromes from the distribution of clinical features among the population.
7. f) Epidemiology helps during the search of causes of the disease. It is done by starting with the discovery of groups within the population with low and high rates of infection. This helps in the testing of the casualties hence discovering the cause of the disease. (Haskins, 8).

3) Natural History of Disease Model

It refers to how a disease progresses in an individual over time in the absence of therapy. For instance, in HIV infection it causes a spectrum of problems that usually begins at the time of primary HIV infection and terminating with AIDs that usually causes death (Berkman, Lisa, Ichirō and Maria 10).

4) Primary prevention of diseases aims to prevent injury or diseases before its occurrence. It is done by prevention of exposure to hazards that causes the injury or disease. An example of such steps is legislation and enforcement to ban control or ban the use of products that are hazardous such as asbestos. Secondary prevention is aimed at reducing the impact of injury or disease that has already taken place. It is done by treatment of the disease or injury as soon as possible to slow the progress, encouraging strategies to prevent recurrence of the disease or injury and the implementation of programs that return the people to their original health status (Berkman, Lisa, Ichirō and Maria 13). An example of such includes regular examination and screening test for disease detection at their earliest stages. Tertiary prevention aims at softening of the impact caused by an ongoing illness or injury. It is done by helping people manage long-term health problems such as chronic diseases. An example includes the creation of support groups that allow members to hare strategies of healthy living.

5) Epidemic

An epidemic is the rapid spreading of an infection to a large area of people in a particular population over a short period (Park 2).

6) John Snow

In the 1800s there was the largest epidemic of cholera in America and Europe that killed several people (Thomas 3). John snow was a physician in London, and he spent several decades studying cholera systemically. He is credited for solving the cholera outbreak that occurred in London in 1854. However, his studies on cholera were extensive more than that. John snow is considered the father of epidemiology today through his research and management of cholera outbreak in London.

7) The attack rate in epidemiology is the measure of the frequency of morbidity or speed of spread of a disease in a population which is at risk. Secondary attack rate documents the difference between transmissions of illness in a community versus transmission in a closed population (Haskins 14).

8)

1. a) The incidence rate is expressed as the number of events per person in one particular time. In a population where there is the prevalence of a certain type of disease, some people will show symptoms of the disease earlier than others (Haskins 18).
2. b) The mortality rate is also known as death rate is the measure of the number of deaths caused by a specific cause disease or condition within a given population scaled to the size of the population per unit time (Haskins 18).
3. c) Case fatality rate is the section of people in a population dying from a particular specific disease among individuals diagnosed with the disease over a certain period. Case fatality rates are used to determine the severity of the disease which is often used to predict the outcome of the disease (Haskins 18).
4. d) The proportional mortality rate is the number of deaths within the population caused by a specific cause or disease divided by the overall number of deaths in the population in a specified amount of time such as a year (Haskins 19).

9) During an outbreak, it’s when the incidence of disease will equal the prevalence. Inference and prevalence data helps in the determination of the impact of an outbreak (Kuo et al. 5).

10) Morbidity rate is defined as the rate of being unhealthy or sick due to poor health status while mortality rate, on the other hand, is defined as the rate at which people die or exist for a certain period.

11) The similarity is that in all the cases, they have a similar denominator in their calculation which is the total no number of people residing in that particular area. However, their difference is that they all cover different areas in the population (Kuo et al. 15). For instance, maternal mortality ratio covers deaths that occur among mothers while infant deaths are deaths occurring among infants.

12) A ratio is a comparison of sizes between two qualities of the same unit while proportion is the equality of two ratios. A ratio is an expression while proportion is an equation that can be solved (Berkman, Lisa, Ichirō and Maria 6).

13) Advantages

1. a) Helps in the representation of the exact number of cases in a population at a specific period.
2. b) Any size of the population can be used during calculations
3. c) Allows comparison in a population that has different sizes without demographic consideration.
4. d) It does not need to consider all factors affecting observed rates.

Disadvantages

1. a) Does not allow comparison of the population that vary in composition
2. b) Population varies in the composition such as age, economic status, and differences in crude rates are difficult to interpret (Berkman, Lisa, Ichirō and Maria 34).

13) It is a quality that is expressed as a ratio or percentage that quantifies the decrease or increase of mortality rates of a cohort study in that specific general population.

14)

1. a) Age-specific rates are total deaths to residents of a particular age group or age found at a specific location divided by the entire population of the same age group or age in the same location for a specific period.
2. b) An age-adjusting rate is an approach of making a fair comparison between that has different age distribution.

The major difference between this two is that age adjusting rate is used to make a fair comparison while the age-specific rate is specific to a particular age.

16) Cyclic variation represents an increase and decrease of health-related events periodically. These variations are usually predictable with some diseases variations being seasonal or migration patterns (Berkman, Lisa, Ichirō and Maria 143).

17) Descriptive epidemiology generates hypothesis and answers the questions where the epidemic is when it occurred, and who are most affected while analytic epidemiology tests the hypothesis. It answers why there is an epidemic and what is the cause (Marzuka and Book 13).

18) Clinical description of a disease describes a disease by identification of its pathological impact on the body after infection while epidemiologic description describes a disease by its signs, symptoms and the possible cause.

Part II

Epidemic measurements and sources should be evidence-based. That is they should be based on research or a survey that was carried out prior (Rothman 4).

External validity is the logical application of scientific conclusion outside the context of a particular study. External validation is essential in the choice of data since, during research, credible data sources are necessary for drawing relevant conclusions (Khorsan, Raheleh and Cindy 12).

Health insurance

Health insurance statistics summarizes the utility, costs, and efficiency of medical goods and services. These statistics are also used to measure the performance of various healthcare organizations. One of the important strengths of these statistics is that they can be used to predict the types of services used most by people. By knowing this researcher can develop relevant measures that can prevent the occurrence of the disease. One of the major weaknesses is that these statistics are not a total representation of the population sine not everyone has health insurance.

Data from medical clinics can be used to carry out cross-sectional studies within a given hospital, and longitudinal studies on patients are distributed geographically. The major strength of this data is that helps researchers understand how diseases are caused and how they can be treated or prevented. A weakness is that this source overrides a patient’s privacy.

Morbidity surveys are used in the evaluation of the general health of the population in a particular area. This survey provides a comprehensive picture of the health status in a specific population. A weakness in morbidity survey data is that the data may not have been collected uniformly across the entire population.

Vital statistics are used to establish disparities in health across different ethnic and racial subgroups within a population. A major strength is that vital statistics cover a large area in the population and it is consistent over time. The weakness is that the data report from history is not validated and also some race or ethnic groups are too small.

Absenteeism data in an organization is used for the detection of an outbreak in a particular organization or school. The strength of this method is that it has the potential of providing patterns of illness that are a server and those that are less server occurring among children in schools or employees in a particular organization. A major weakness is that it is time-consuming to go through all the data and establish a pattern.

Disease registers are used in prevention and control of diseases that are highly infectious. The strength of this approach is it has already preventive, and control measures are already put in place. The major weakness is that it is limited to diseases that have already been documented new disease, however, are not.

Hospital and clinic statistics are used in the detection of infection and overall mortality rate in patients due to an infection or disease. The strength of this approach is that the source is credible since they are evidence-based. A weakness is that hospital and clinical statistics are limited to only to hospital settings and may not cover a huge geographical region (Pope, Daniel, and Debbi 19).

The bibliographic database provides an index of articles from journals in multiple fields, and it includes abstracts, citation and usually a link to the full text. The bibliographic database includes GALILEO database social science abstract, meta-database, and census bureau database (Waffenschmidt et al. 3).

Understanding of distribution and dynamics of disease provides useful information on how to prevent the spread of disease, design an intervention plan and control the prevalence of the disease in the population (Rothman 13).

An epidemiologic study is the analysis of determinants and distribution of disease and health conditions within a particular population. Epidemiologic study cycles are the sequences of the process that is necessary for caring out an epidemiologic study. For instance, the descriptive study cannot follow a analytic survey because a hypothesis needs to be developed first for it to be tested.

1. a) Cross-sectional design is a type of observational study in which the investigators measure the outcomes and the exposures of the participants in the study at the same time. This design is used to prove or disprove assumptions however its limitation is that it is not used to analyze behavior (Pope, Daniel, and Debbi, 13).
2. b) Case-control design is used to aid in the determination of exposure is to an outcome. A major strength of this design is that it is efficient for diseases with a long latency period or diseases that are rare. Its limitation is that this design has selection biases (Pope, Daniel, and Debbi 16).
3. c) Prospective cohort design also called longitudinal cohort study includes following similar individuals or groups being studied over time that are different due to certain factors to determine factors affecting rates of outcomes. One of the strengths is that several outcomes can be measured for any single exposure. The limitations of this design are that it is time-consuming and costly (Pope, Daniel, and Debbi 18).
4. d) Clinical trials are the development of experiments as well as caring out of observations medically while trying to intervene in an epidemiologic case. One of the strengths of this design is that it provides evidence that the intervention is effective. A limitation of this design is that researchers invest much time and resources during the investigation (Pope, Daniel, and Debbi 19).
5. c) Community trials designs are appropriate for evaluation of lifestyle intervention choices in a particular community. The strength of this design is that it can be used to carry out intervention in a whole community while its weakness is that community trial design is sometimes not as effective as a clinical trial (Pope, Daniel, and Debbi 21).

8) Ecological studies are an observational study that involves measurement of at list one variable in a group level. This study is used during the initial investigation of a hypothesis. An example is environmental measures which involve observation of physical characteristics of a particular place in which members of each group work or leave being observed. Limitation of this study is that there is a potential difference between the systems used for measurements of exposure in different areas (Johns et al. 14).

9) A case-control study involves comparison of patients who have a disease or an outcome of interest with patients or those who do not have the disease or outcome while comparing how frequent the risk factors are being exposed to the patient’s group. It helps in the determination of the relationship between risk factors and the disease (Rothman 21).

Advantages

It is good for studying new diseases or conditions.

Less time consuming because the disease has already been established.

Looks at multiple risk factors simultaneously.

Can answer questions that other studies cannot answer.

Disadvantage

It is some cases it might be difficult to find a suitable control group.

It is not suitable for performing diagnostic tests since it is already known those who have the condition and those who do not.

It is a retrospective study, and this type of studies has a problem with the quality of the data because they depend on the memory of the people with the condition.

10) The odds ratio is used to compare an outcome in the presence of a risk factor or some exposure. However, odds ratio give good approximation when it is equivalent to the odds ratio.

11) A cohort study is a study design where samples are prospectively followed and are subsequently evaluated concerning outcomes or disease that are conducted to determine what are the risk factors associated with it (Rothman 14). One of the examples of cohort studies is the Nurses’ health study that was set up in 1976 and was used to investigate the potential consequences of using oral contraceptives. Another example is Framingham heart study that recruited over 5,209 participants both male and female in 1948 used to determine risk factors for cardiovascular risks.

12) A major characteristic of this study is that investigators identify a point in time when there are no certain desired outcomes in a population and compare them with the incidences of the outcomes that are of interest among groups that are exposed to a certain risk factor (Rothman 23).

Advantages

It allows examination of multiple effects of a single exposure

It facilitates studying of rare risk factors or unusual exposures such as adverse effects of treatments or drugs.

It also allows calculation of incidences of disease among the exposed groups to calculate absolute risk, risk difference, attributable proportion, and relative risk.

Disadvantage

Allows a large number of subjects for a long time.

They very expensive and time-consuming

It may be difficult to identify and compare an appropriate cohort study (Rothman 24).

13) Two major intervention studies are community interventions and controlled clinical trials. Controlled clinical trials involve individual subjects while community interventions involve an entire group. Treatment is allocated to individual subjects while community trials are allocated to groups of subjects (Rothman 45).

14) Stages of evaluation

Planning

Mainly entails collection of data in a study to asses a situation before the development of a program. It is necessary to define the objectives of the evaluation based on the data collected and the consideration of different evaluation methods that could be used (Szklo and Javier , 2).

Choosing of the evaluation method

There are different types of methods that can be used in caring out of the evaluation. This step involves the selection of an appropriate evaluation method based on the data collected at the initial planning phase (Szklo and Javier 2).

Implementation

It entails running the program and ensuring that it is monitored. Program monitoring ensures that the program that is implemented was the one chosen and it is running efficiently. Process evaluation refers to the activities that are done to measure if the program is accomplishing its intended goals (Szklo and Javier 3).

Dissemination and feedback

It entails feeding of evaluation results back into the planning and implementation phase as well as considering ways in which the results can be shared with different parties that are interested (Szklo and Javier 3).

Part III

1)

1. a) Hand hygiene. The personnel involved in controlling the infection should wash their arms and forearms before performing any procedure in attempts of controlling the disease.
2. b) Environmental hygiene. Most conditions have common sources of contamination therefore if hygiene is maintained disease infection rate is reduced
3. c) Screening and coloration of patients should be part of the controlling planning. This is important to ensure that there is no cross infection happening.
4. d) Vaccination. Medical staffs that are controlling a certain type of infection should have been vaccinated before handling the disease. It prevents further infection.
5. e) Surveillance through surveillance the medical personnel can gather data about the infection measure the outcomes assess the process and take required steps to prevent the disease.

Antibiotic stewardship. Misuse and overuse of antimicrobial drugs can put patients at risk of getting infections.

Care-coordination. Coordination of care between medical staffs is essential during controlling of an infection (Kimberlin et al. 13)

It is an indirect form of protection from disease that occurs in a community or a large percentage of the community that have become immune to that particular disease. This, however, provides immunity also for those who are not immunized (Notkins 46)

Isolation is ineffective when the transmission is not asymptomatic and if the incubation period of the illness is long, such as HIV/AIDs (Bhopal 108).

The population at risk is the part of a community which is at risk of contracting a particular infection (Skolnik 46).

1. a) Acquired immunity
2. b) Natural immunity
3. c) Active immunity
4. d) Passive immunity (Notkins 5)

6) Screening is an investigation or evaluation of someone or something to identify the possibility or presence of an undiagnosed disease (Szklo and Javier 440)

7) The purpose of screening is to detect potential health disorder or disease among people who do not show any symptoms (Szklo and Javier 441).

8) They are two technical properties of a test that are used to indicate the quality and usefulness of a particular study (Bhopal 85).

9) These are statistical measures for assessing the performance of binary classification tests. It is a trade-off because two studies need to be carried out and compare them to a gold standard (Bhopal 667)

10) Screening tests should be done as soon as one is suspected of having a certain disease or infection (Szklo and Javier 440)

11) Exposure to the risk factors that cause the disease is the main reason why one would participate in a screening program (Bhopal 107).

12) Test of significance is used to evaluate the probability of something occurring randomly from a random sample drawn from a particular population of interest. Measures of association are used to quantify the relationship between two or more variables (Bhopal 200)

13) It involves scoring the severity of clinical symptoms, transmission rates of the infection, the number of cases reported and the source of infection (Bhopal 305)

14) Some of the pathological effects triggered by in an infection include; fever, fatigue, headache, and inflammation which are caused as a response of the immune system (Kimberlin et al. 13).

15) Transmission can be direct or indirect. Direct infection mechanism occurs when the bacteria is directly introduced into the body. It can be through ingestion of contaminated food or inhalation of contaminated air. Indirect transmission occurs via a vector that may be through a vector such as mosquitoes (Kimberlin et al. 8).

16) a) Airborne-it occurs when then infectious agents are carried by dust that is suspended in the air.

1. b) contact- transmission takes place when an infected person touches, or they exchange body fluids with an uninfected person.
2. c) vector-borne: occurs when the infectious agent is inhibited or reserved in a vector for replication, and it is later transmitted into a host through a blood meal an example is a mosquito.
3. d) Vehicle bone occurs when a non-living object carries the infectious agent from one host to another.
4. e) Direct transmission is when one is directly in contact with an infected individual and directly inhales their infectious breaths or gets into contact with droplets or fluids from the infected individual.
5. f) Indirect contact infection occurs when infected sneezes, or coughs, therefore, spreading the infectious agents in the air (Kimberlin et al. 10).

17)

Prepare for field work

Establish existence of an outbreak

Verify diagnosis

Construction of a working case definition

Systematically find the cases and record information

Performance of descriptive epidemiology

Development of hypothesis

Evaluation of the hypothesis epidemiologically

Reconsider, re-evaluate, and refine the hypothesis

Compare with laboratory and environmental studies

Implementation of control and preventive measures

Initiation and maintenance of surveillance

Communication of findings to relevant bodies (Petzold et al. 925).

18) Economic, socio-political and ecologic factors are the main reasons for migration in a community. Violence which is usually caused by ethnic or religious intolerances is also among the reasons for migration. Ecological changes are also among the reasons since these changes have the potential of worsening food security and causing disease outbreaks (Petzold et al. 78).

19) The ecological study design is an observational study design that is used to measure the incidences and prevalence of certain diseases. Cohort study design is carried out to determine the risk factors of as particular disease or outcome. A cross-sectional study is an observational study that is used to measure the outcomes and exposure of risks of the study participants at the same time (Creswell et al. 12).

20)

Identification of the study subject

Obtaining of baseline data on the exposure including measuring of the exposure at the start

Selection of the sub-classified cohort, an unexposed or control cohort which is to be the comparison group.

Follow up which entails measuring of outcomes using records, examination or interviews.

The analysis is done where the outcomes are compared and assessed (Creswell et al., 56)

21) Internal validity represents a causal relationship between the subject’s variables in a study while external validity contains procedural variables and it represents the generalizability of the study and how well it is generalized in a study (Soy 78).

22) Random error is a measurement error that a researcher does due to his/her inability to taking the same measurements. Factors that contribute to this error include poor calibration of instruments, poor observation methods, and environmental interference with the measurement process (Soy 38).

23) Systemic errors occur due to persistent prothe blem throughout the research. Factors causing this error include repeated errors that are caused by faulty experiments design or faulty equipment (Soy 45).

24)

1. a) Review the guidelines for conducting the research
2. b) Draft the study before collection of data
3. c) While doing the research one should keep the records detailed
4. d) All data should be incorporated in the research without leaving out anything.
5. e) Limitations should also be included in the research. These include the areas that might affect the study (Szklo and Javier 418)

25) Confounding variable is an outside value that changes the effect of the independent and dependent variable. Methods of controlling confounding include; matching, randomization of data and restriction (Soy 18).

26)

Simple: the tests should be easily learned and performed. Screening that can be done by a non-physician or medical personnel.

Rapid: the tests should take a short time to administer and the result made available soon.

Inexpensive: the lower the cost of the screening program the more likely it will be beneficial (Szklo and Javier 421).

27)

Recalibration of screening instruments to minimize errors that are caused by the wrong calibration

Retraining of screeners that do a test that requires assessments by human such as blood pressure reading. It will improve precision during testing.

Utilization of different tests. It is important in some situations to have more than one way of measuring the desired outcomes. If one assay performs poorly, another is used.

Due to variability in some measures taken, it is easy for some measures to take to be misclassified. However, if more than one test is done, an average can be done, and the desired outcome be recorded (Szklo and Javier 435).

28)

Infectivity is the capacity of an infectious agent to trigger the host’s immune system.

Virulence is the infectious agent able to cause harm to the host.

Resistance is the ability of an infectious agent to survive adverse environmental conditions in the host’s body.

Pathogenicity is the capacity of the infectious agent to cause disease in an infected host.

Toxigenicity an infectious agent can produce poisons or toxins.

Antigenicity is the ability of an infectious agent to induce antibody production in the host (Kimberlin et al. 16).

29) Genetic epidemiology focuses on how genes produce disease in human beings while molecular epidemiology focuses on molecular determinants of health and how they might cause disease (Szklo and Javier 34).

30) Stress is a risk factor for some chronic diseases such as heart condition. When one is under stress, their immune system becomes unable to respond to hormonal control and consequently reacts by producing levels of inflammation, therefore, promoting the disease (Lovallo 2).

Part IV

1. a) Individual odds in a case study is the likely hood a researcher’s hypothesis to be true during a particular study.
2. b) The odds ratio is a measure of association in a case-control study. Odds ratio show how high risks of exposures are among cases compared to the controls of that particular study (Keogh, Ruth & David 13).

2)

1. i) Individual risk determines the rate of disease infection by a person at a particular place and time.
2. ii) Relative risks are used in the identification of the risk factors for disease.

iii) Attribute risks are used in the development of disease prevention mechanisms (Tigchelaar et al. 84).

3a) In research a variable is a quantity that keeps changing. An independent variable is a quantity that mainly affects the dependent variable. It is usually manipulated by a researcher during the research.

1. b) A dependent variable, however, is a variable that a researcher is investigating and is interested in. The changes to this value are what the researcher is investigating.
2. c) Mediator variable affects the relation between criterion and predictor variable this variable can be qualitative such as race or sex.
3. d) Confounding variable is the outside effect that is not part of the research, but it affects both independent and dependent variables (Mehta 15).

4 a) an analytic design of the study in research is used in identification and quantification associations in a review, test the hypothesis and determine if there is any association between exposure and onset of disease in a study. These studies usually compare two or more sets of data.

1. b) The descriptive study provides a platform for analyzing and organizing data to understand the variation in disease occurrence frequency overtime geographically and how the disease also varies among people based on their characteristics.
2. c) Experimental design gives the researcher ability of testing their hypothesis by reaching conclusion about the relationship between dependent and independent variables.
3. d) The interventional design is a randomized control trial usually performed in clinical trials and laboratories to establish the beneficial outcomes of a drug or a particular procedure (Yin 9).

5) Persons lost to follow-up refer to patients who were participating in a clinical trial, but they have become lost at the point of follow-up (Piantadosi 46).

6) Persons year of observation is a denominator that is used in a cohort study to estimate the rate of a particular disease during a certain defined period (Piantadosi 18).

7)

1. a) Relative risk is used in the comparison of likelihood or chances of an event occurring between two different groups.
2. b) The difference between the rate of incidence in exposed and a non-exposed group.
3. c) Odds ratio defines the relationship between exposures and outcomes.
4. d) Sensitivity helps in ruling out the possibility of occurrence of disease.

8) Type A behavior an individual is competitive, aggressive and hostile (Hollands et al. 3)

9) Life stress it is physical, emotional or mental tension or strains that one goes through every day (Lovallo 5).

10) Reliability is another term of consistency when the person gets the same results after several tests. Validity is a measure of what it is supposed to be real (Neuman 14).

11) Time, place and person variables are used in the detection of patterns in disease occurrences.

12) Natural history of the disease is important for the designing of interventions both chemotherapeutic and environmental to reduce the prevalence of disease in a particular circumstance (Bhopal 78).

13) It is a tool used to investigate the distribution and occurrence of mental disorders across people, time and space and to investigate the causes and the related consequences (Bhopal 103).

14) Defines the degree to which a person’s and environmental characteristics match.

15)

1. a) indirect method of difference
2. b) Method of agreement
3. c) Method of concomitant variation
4. d) Method of difference
5. e) Method of residues (Arkin et al. 16)

16) Acculturation is the process in an environment in which a new person adapts to behaviors that are common in a host community, and it leads to changes in diet patterns, environmental exposures and the physical activity levels (Firills et al. 336).

17) It is a concept that describes the body’s adaption to stress.

18)

1. a) The temporal relationship between the cause and the disease
2. b) General consideration
3. c) Global sorting d) Lifesaving intervention
4. e) Individual assessment (Friis, Robert and Thomas 97).

19) The incidence rate is a measure of the probability of the occurrence of disease while prevalence rate is the rate is the actual number of cases associated with the disease during a particular period (Creswell et al. 38).

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