Equations and definitons

Question 1

Define descriptive and analytic epidemiology

Answer 1

Descriptive epidemiology can identify patterns among cases and in populations by time, place and person

Analytic epidemiology, compares caharacteristsic between groups or populations and attempts to find a causal relationship or association for differeences, and quantify this relationshp

Question 2

Provide examples of occupational hazards

Answer 2

Hazard is any source or situation that has the potential to cause harm to workers.

Situational hazards: psychosocial(short term overload, failing to cope, sudden horror or terror, bullying and harassment), safety (situations that can cause accident, trauma or injury; slips, trips and falls; workplace layout; heigh related hazards), ergonomics (manual handling, repetitive work, long working duration, posture and body movements), mixed basis (sick building syndrome, fire hazard)

Hazards of specific agent/form of energy: chem (gas, fume , particulate, mied eg machine smoke and tobacco smoke), phys (noise, electricity, lighting, barometic pressure, radiation, vibration and temperature), biological

Question 3

Define occ dest of health

Answer 3

Various factors related to a person’s work or occupation that can affect their physical, mental, and social well-being
These determinants include aspects of the work environment – hazards or occupational factors
Other occupational determinants of health include
type of job
work hours
income and job security
access to healthcare and other resources

Question 4

Define social determinants of health

Answer 4

Social determinants are social features that increase the risk of illness through their influence on biomedical and behavioural factors, as well as impacting on health directly.

Social determinants are referred to as the “causes of the causes of illness”

The social determinants of health are defined by the World Health Organisation as:

“The circumstances in which people are born, grow, live, work, and age, and the systems put in place to deal with illness. The conditions in which people live and die are, in turn, shaped by political, social, and economic forces.”

Question 5

Calculate odds ratio

Answer 5

same as risk ratio
Definition:

Question 6

Calculate risk ratio

Answer 6

Recall ratio is a comparison of two independent variables i.e. A/B

Risk ratio or relative risk, calculated in studies where people are followed over time, and the development of an outcome is then measured e.g. cohort or RCTs.

RR = (incidence in the exposed group) / (incidence in the unexposed group)

To calculate the risk ratio from a contingency table:

Calculate the incidence in the exposed group (a/a+b)
Calculate the incidence in the unexposed group (c/c+d)
Divide the answer from (1) by the answer in (2)

Formula:
RR = (a/a+b) / (c/c+d)

where a is exposed and disease, b is exposed and no disease, c is no exposed and disease, d is no exposure and no disease

Question 7

Calculate rate difference

Answer 7

The rate difference is calculated by subtracting the incidence rate in the comparison group from the incidence rate in the group of interest. As it is an absolute measure two compare the rates in two groups, the units of measurement are the reported (and are the same as the units used in reporting the rates).
The correct answer is: 90.1-44.9 = 45.2 per 1000 person years

Question 8

Interpret 95% CI

Answer 8

crossing 1

Question 9

Calculate se

Answer 9

The standard error is therefore the variation in means from multiple sets of measurements.
Sd/ root(n)

Question 10

Define determinants of health

Answer 10

Health determinants can be defined as:

(i) attributes, characteristics or exposures that increase or decrease the likelihood that a person will develop a disease or disorder.

(ii) a broad range of personal, social, economic and environmental factors that determine individual and population health.

Determinants of health include both risk factors and protective factors.

A risk factor is any factor which increases the likelihood of a person developing a health disorder or health condition.

Protective factors can reduce the likelihood of developing disease, or slow the progression and severity of the disease.

Determinants may be modifiable or non-modifiable.

Modifiable factors are those that can be changed, such as lifestyle, social and environmental factors.

Non-modifiable factors are those that cannot be changed, such as age, sex (biological, not gender), and ethnicity.

Question 11

Defien environmental determinants of health

Answer 11

Environmental health addresses all the [physical], chemical, and biological factors [external]to a person, and all the related factors impacting [behaviours]. It encompasses

the [assessment ] and control of those environmental factors that can potentially affect health. It is targeted towards preventing [disease ] and creating health-supportive

[environments].

Question 12

Interpret p values and explan why they might be problematic

Question 13

Define the study designs, their benefits and disadvantages

Answer 13

pidemiological study designs

Case series: describes the characteristics of a group of people who have the same disease or exposure.
Ecological studies: Ecological studies collect data at the population level, for example measles rates in different countries. The disease and exposure of interest are measured in different populations and their relationship examined.
Cross-sectional surveys: information is collected from a defined population at a single point in time providing a "snapshot" of the health status of a population. Often involves collecting information using questionnaire. Often referred to as prevalence surveys.
Case-control studies: groups of diseased (cases) and non-diseased (controls) subjects are selected and compared.
Cohort studies: groups of exposed and non-exposed individuals are followed over time to measure the development of disease.
Intervention studies: study participants are randomly allocated to treatment and control groups and the outcomes in each group are compared.

Question 14

List and describe the different incidences

Answer 14

• cumulate
• and incidence rates

Question 15

List factors that influence incidence

Question 16

Describe and provide examples of the epidemiological triad

Answer 16

The epidemiological triad is the traditional model to understand infectious disease causation. It shows the interaction between:

an infectious agent, 
it's potential host, 
the transmission process (how the disease is spread) 
and how all of these may be influenced by the environment.

An epidemic may therefore result from:

A recent increase in amount or virulence of the agent,
The recent introduction of the agent into a setting where it has not been before,
An enhanced mode of transmission so that more susceptible persons are exposed,
A change in the susceptibility of the host response to the agent, and/or
Factors that increase host exposure or involve introduction through new portals of entry

Question 17

Define surveillance

Answer 17

Surveillance is defined as:

“The ongoing systematic collection, analysis and interpretation of health data essential for planning, implementing and evaluating public health data”.1

The goal of public health surveillance is to provide information that can be used for action by public health personnel, government leaders, and the public.

Active, passive, surveillance and sentinel:
n passive surveillance, laboratories, doctors or other healthcare professionals regularly report cases of disease to the local or state health department. Notifiable diseases such as measles are reported under passive surveillance systems

In active surveillance, local or state health departments initiate the collection of specific cases of disease from laboratories, doctors or other healthcare professionals. An example of active surveillance is the screening of hospital patients on admission for nasal colonisation with MRSA.

Sentinal surveillance: health events are reported by health professionals who are part of a limited network that is deliberately selected to represent a geographic area or specific reporting group. It is used when high quality information is needed about a disease that can not be obtained through passive surveillance.

An example is the Victorian Sentinel Practice Influenza Network, which is a general practice-based program that provides information about the proportion of patients with influenza-like illness

Syndromic surveillance: focuses on one or more symptoms rather than a doctor diagnosed or laboratory confirmed disease. Syndromic surveillance is commonly used to improve early detection of outbreaks.

An example is the Flutracker system, that collects weekly information on flu-like symptoms therefore providing an early warning of increased activity before data on confirmed cases is available.

Question 18

List examples of notifiable diseases

Answer 18

• campylobacterioriss
• salmonellosis
• measles
  -anthax
• Hepatities BCD
• Chlamydia
• Malaraia
• Legionelloiss
• CJD
• plague

Question 19

Calculate incidence rate

Answer 19

The incidence rate of avoidable hospitalisation in Aboriginal children was twice that of non-Aboriginal children. The rate ratio is a relative comparison of the incidence rates in the two groups. The incidence rate in the group of interest is divided by the incidence in the comparison group. As it is a ratio, there are no units of measurement.
The correct answer is: 90.1/44.9 = 2.01

i.e no units

Question 20

Define crude mortality rate, and distinguish with age adjusted mortality rate

Answer 20

The crude mortality rate reflects the mortality experience and age distribution of a community, whereas the age adjusted mortality rate eliminates any differences in the age distribution. If community A’s age-adjusted mortality rate is lower than its crude rate then that indicates that its population is older.

Question 21

TRUE OR FALSE Cause-specific mortality rate uses mid year population in denominatior

Answer 21

TRUE
but maternal mortality, age-specific, and infant do not

Question 22

Define neonatal mortality rate

Answer 22

The neonatal mortality rate is the probability of dying within the first 28 days of life per 1000 live births.

Question 23

What is a key feature of incidence

Answer 23

Incidence is the number of new cases that occur during a specified period of time in a population at risk of developing the disease.

Question 24

Describe period prevalence

Answer 24

Period prevalence is the proportion of existing cases in a defined population over a specified period of time.

Question 25

Define cumulative incidence

Answer 25

Cumulative incidence is the proportion of an initially disease-free population that develops disease during a specified time. The cumulative incidence is calculated as 15/1000 giving 1.5% (or 15 per 1000 women).

Question 26

What is the difference between a rate and a proporiton

Answer 26

A proportion is a comparison of two independent varaibles, whrea numberot is included indenominator. EG prev, incidence, mortality

Rate is a special case of proportion, includes a specific time period

Question 27

Definition of prevalence

Answer 27

The proportion in a defined population who have a specific disease at a certain point or piod of time: no of people with disease ata given time/period divided by no in totatl popoulation at time

Can be expressed as percentage or as per 100, 1000

Question 28

Distinguish between cumulative incidence and incidence rate

Answer 28

• cumulative: proportion of new cases of disesase in population i in a fgiben period
• divdided by pop at risk in psecifc time priod

Rperesents risk of developing diseae
percent, %/yr, per 1000, per 100k

Inc rates: how hast new cases of disease are occuring in pipulation aat risk
multiplied by time interval

expressed in person-time units:

note: 100 new cases of cholera, divided by population at risk of 5000, times 5 years

= 0.004 new cases per year
OR 4 per 1000 person years

Assumption in calculation= all persons followed for total interval

Question 29

List the two factors within the envirionemnt which can affect health

Answer 29

• natural environemnt
• built environment

Question 30

List the principle exposures of environmental health

Answer 30

Bio
Phys
Chem

Question 31

Describe some environmental health risk assessments

Answer 31

• dose respinse
• exposure
• hazard*’
• risk characterisation: Risk characterisation examines how well the data support conclusions about the nature and extent of the risk from exposure to environmental stressors.

Question 32

Define risk managemtn

Answer 32

Risk management involves consideration of reducing the hazard at source, removing exposures at the individual level, and removing exposures at community levels.

Idnetify and assesss, develop control measures to reduce it, and monitor effectiveness of control measures

Once the hazard has been identified - risk assessment
Probability, the likelihood of exposure to the hazard
Level of severity of disease or injury that occurs
A combination of both
Influenced by
Hazard nature
Dose-response relationship
Workplace policy
Individual factors

Question 33

List the steps to surveillance process

Answer 33

• data collection
• data analysi
• data interpretation
• data dissemination
• link to action

Question 34

List some categories of epidemic and outbreak disease patterns

Answer 34

Sporadic refers to a disease that occurs infrequently and irregularly.

Endemic refers to the constant presence and/or usual prevalence of a disease or infectious agent in a population within a geographic area. In other words, it is the amount of a particular disease that is usually present in a community and is often referred to as the baseline level. For example, malaria is endemic in much of Africa.

Hyperendemic refers to persistent, high levels of disease occurrence.

Epidemic refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area.

Outbreak carries the same definition of epidemic, but is often used for a more limited geographic area.

Cluster refers to an aggregation of cases grouped in place and time that are suspected to be greater than the number expected, even though the expected number may not be known.

Pandemic refers to an epidemic that has spread over several countries or continents, usually affecting a large number of people. Examples are the influenza pandemics of 1918, 1957 and 1968; HIV and multi-drug resistant tuberculosis

Question 35

Describe patterns of epidemic

Answer 35

Epidemics can be classified according to their manner of spread through a population. There are two main types:

Common-source
    Point
    Continuous
    Intermittent
Propagated

A common-source outbreak is one in which a group of persons are all exposed to an infectious agent or a toxin from the same source.

A propagated outbreak results from transmission from one person to another.

The progress of an outbreak is studied using an epidemic curve. This is a plot of the number of cases of disease against time relative to the date of onset. From it’s shape we can identify the type of epidemic.

Question 36

Describe the hierarchy of evidence

Answer 36

The hierarchy of evidence

Meta-analysis of randomised controlled trials
Randomised controlled trial
Cohort study
Case-control study
Cross-sectional study
Ecological study
Case series

Question 37

List the advantages and disadvantages of case series

Answer 37

Advantages

Disadvantages

Describes the demographics, presentation or prognosis of people who have a particular disease.

Has no comparison group.

Can draw attention to an emerging issue and lead to confirmatory studies using higher quality study designs

Question 38

List the advantages and disadvantages of ecological or correlational studies

Answer 38

Ecological level variables may be:

aggregrate measures: summaries of observations derived from individuals (e.g. incidence of a disease, proportion of smokers, area level deprivation indices), 
environmental measures (e.g. air pollution level or hours of sunlight) 
global measures for which there is no distinct individual level measure (e.g. Gross Domestic Product, population density)

Advantages:

Useful for comparing health between different populations or over time

Useful for highlighting issues that can be investigated in future studies

Inexpensive and quick as can use existing sources of data, such as published statistics

Useful in environmental epidemiology where we often can not measure exposures at the individual level for large numbers of subjects

Useful for the evaluation of the impact of new policies, programmes and legislation on the population

Negatives:

Has no comparison group.
The people who are exposed may not be the same ones who experience the outcome. If the associations detected at group level do not hold on an individual level, the study suffers from a type of bias known as ecological fallacy.

Question 39

Describe cross-sectional studies

Answer 39

In cross-sectional studies, information is collected from a defined population at a single point in time without any follow-up, providing a “snapshot” of their health.

Because they measure health status at a point in time, they are often called prevalence studies.

Cross-sectional studies usually involve asking participants a series of questions using a questionnaire.

Cross-sectional studies may be:

descriptive: they measure one parameter, e.g. the prevalence of type 2 diabetes in adults over the age of 40y (often called prevalence studies.)
analytical: the measure exposure associations with outcomes, e.g. the association between obesity and type 2 diabetes in the same population.

Advantages:
Relatively inexpensive and easy to conduct
Can provide information on multiple exposures and outcomes
Assess the health needs of a population
Useful for studying asymptomatic conditions where patients may not present to doctors, such as high blood pressure. The clinical iceberg is a recognised phenomenon in which medical services are only aware of symptomatic patients, i.e. those above the water line.

Diasadvantages:
Cannot determine causality: measurements of the outcome and exposure are made at the same time, cross-sectional studies cannot be used to determine whether a particular exposure caused the disease. In addition, the exposure may be secondary to the disease (reverse causality).
Selection bias: subjects with an interest in the topic may be more likely to volunteer to participate. Selection using random sampling may still result in bias if the response rate to selection is low.

Recall bias: cases of disease may be more aware of suspected exposures than participants without disease

Confounding: association with a third variable that provides an alternative explanation for the observed association between the exposure and the outcome.

Question 40

Describe case control studies

Answer 40

Case-control studies start with cases of a disease and uses a comparison of controls, who are similar to cases but do not have the disease.

Both groups are asked about their exposure to previous risk factors. Sometimes exposure information is extracted from records.

Case-control studies compare the frequency of exposure to a suspected risk factor in cases with the frequency of exposure to that risk factor in controls. The summary measure expressing the association between the exposure and disease is known as the odds ratio (see below).

Advantages:
- evaluate many different exposures
- useful fro rare diseases becuase they start off with caes
- quick and cheap tp perform

Disadvantages:
- not good for rare exposures: bec may involve small numbers
- control selection: can be dif to obtain controls that adequately represent the population that cases come from
- info bias: recall bias and observer or interviewr bases (if case and control, info not comparable)
- confounding
- reverse causality: outcome already occurred, dif to tell if exposure preceded outcome
- selection bia: arises if cases and controls are no choen independently of the exposures being studied

\
eg smoking and lung cancer

Question 41

Describe cohort studies

Answer 41

In cohort studies a group of people are followed over time to study what happens to them.

Information about exposures are usually measured at the start of the study among people who have not yet developed the disease outcome of interest. They are then followed over time to evaluate the occurrence of the outcome. This is known as a prospective cohort study.

Sometimes, a retrospective cohort study is conducted where the disease has already occurred and investigators can collect exposure data from pre-existing records. This design is useful for studying long-term exposure effects as the investigators do not need to wait for the disease to develop in a prospective study.

Risk ratio

The main advantage of cohort studies is that the time sequence of events can be determined.
- exposure information is measured before the onset of disease so the temporal relationship between exposure and outcome is clear
- provide a direct measure of incidence (risk)
- among observational studies, cohort studies provide best evidence that an exposure-outcome association is causal.
- can assess multiple exposures and multiple outcomes allowing sub-analyses to be conducted

Disadvantges:
- Time consuming and expensive as can involve a large number of people being followed for many years.
- not suitable to study rare diseases
- loss to follow up bias: type of selection bias – move, oose contact, grow tired, become too ill
- confoudning: the exposed and unexposed groups of participants will differ on factors other than the exposure being investigated.

Question 42

Describe RCTs

Answer 42

Randomisation is important because it ensures that the two groups are similar on all aspects (e.g. age, sex, general health, socio-demographic factors) other than the intervention. If one group were in some way less healthy than the other at the start this might make this group look worse even if the intervention had no effect.

Ideally, neither the participants nor the investigators should know which intervention group patients belong to (called double blinding) so that neither of them can influence the outcome of the study.

Best for intervention studies

RR or hazard ratio: comparing incidence rates rather than cumulative incidences

Advantages:
- good evidence of causality - strongest study design that an intervention led to the outcome.
- Randomisation - ensures that both groups have an equal chance of receiving the intervention and that they have similar characteristics. The effect of the intervention can be studies without other factors influencing the outcome (confounding).

Disadvantages:
- Measurement bias may arise if double blinding can not be ensured.
- May need to include a large number of participants.
- May not be suitable in situations where not giving an intervention may be inappropriate or unethical. Can allocate people to harmful exposures.
- can be expensive
- randomisation does not guarantee group equivalence if the numbers of participants are small