Epidemiology 1 Flashcards
(108 cards)
1
Q
What is an epidemiological transition?
A
A decline in total mortality and a significant reduction in infectious diseases, which increase the relative role of chronic non-communicable diseases
2
Q
What is clinical medicine concerned with?
A
The cases of disease and the disease burden for the individual patient.
3
Q
What is epidemiology concerned with?
A
Disease rates and the burden of disease in populations
4
Q
What are the distal and proximal risk factors for cardiovascular disease?
A
- Socioecomic and environmental factors, eg. Social environment, pollution, and sanitation
- Behavioural factors and infections
- Physiological pathways (eg. Raised blood pressure, diabetes, and thrombosis)
5
Q
What is a case-control study?
A
An observational study where two groups are compared to see if a certain factor increases the risk of a disease. This helps to determine if an exposure is associated with an outcome.
6
Q
What are the advantages of a case control study?
A
They are quick, cheap, and useful in investigating outbreaks of infections diseases.
7
Q
Define prevalence
A
Frequency of a disease in a population at a moment of time
8
Q
Define incidence
A
The number if new infections within a population over time
9
Q
Define mortality
A
The number of deaths in a population due to a specific condition over a given time
10
Q
Explain the relationship between prevalence and mortality
A
As mortality decreases, the prevalence increases as there are more people alive with the disease.
11
Q
What are desriptive studies?
A
They describe the distribution if factors or disease in relation to person, place and time.
12
Q
What is routine data?
A
Data that are routinely collected and recorded in an ongoing systematic way, often for administrative or statutory purposes and without any specific research question in mind at the time of collection
13
Q
What are the problems with calculating prevalence?
A
- The people available (and not available) to collect the data at the time may result in participation bias
- There may be contamination - people from a different area present by chance
- May be self reporting errors if the patient is embarrassed about something
- Have to consider the sensitivity and specificity of the test being used
14
Q
How do you calculate incidence?
A
New cases / total cohort population
15
Q
What are the 4 possible causes of correlation?
A
Causation, confounding (other variables), bias, chance
16
Q
How do you calculate attributable risk?
A
Incidence in exposed - incidence in unexposed
17
Q
Define attributable risk
A
A measure of the exposure effect that indicates on an absolute scale how much greater the frequency in the exposed group is compared with the unexposed, assuming the relationship is causal.
18
Q
When is the attributable risk useful?
A
When evaluating the impact of introduction or removal of risk factors. it indicates the number of cases that could be prevented if exposure were eliminated.
19
Q
What is the difference between a cohort study and a case control study?
A
- A cohort study is where participants are selected based on exposure to a risk factor and they are followed over a period of time.
- A case-control study is where participants are chosen based upon the outcome of interest, and they are asked about exposure.
20
Q
Define count
A
The number of cases of the disease or condition in a population, a simple count of affected individuals.
21
Q
When do you calculate relative risk?
A
Relative risk is calculated used in cohort studies. A measure of association between an exposure and a disease. It can be used as the incidence of disease in exposed and non-exposed groups are known.
22
Q
What is the outcome?
A
The event of interest in a study (eg. the disease)
23
Q
When do you calculate odds ratio?
A
This is calculated from a case control study as patients are selected on basis of disease status. The odds of exposure is calculated.
= Cases exposed/unexposed + controls exposed/ controls not exposed
24
Q
Define the p-value
A
The probability that data were obtained by random error or chance. e.g. p<0.05= less than 5% chance.
25
What is standardisation?
A method for controlling the effect of confounding at the analysis stage of a study.
26
Define stratification
A method of controlling the effect of confounding at the analysis stage of a study, calculating risk separately for each category of confounding variable.
27
Define matching
A method for controlling the effect of confounding at the design stage, where controls have a similar distribution of potential confounding variables as the cases.
28
What is exposure?
The thing hypothesised to have an effect on health.
29
What is a control?
The person without the outcome under study, or a person not receiving the intervention.
30
Define a systematic review
Reviewing all the evidence available concerning a cleary formulated question using systematic and explicit methods to:
- Identify
- Select
- Critically appraise research
- Collect data
- Analyse data
31
Why is it good to conduct a systematic review?
- There are many available papers to review, and the best independent studies can be used
- Differences between studies can be explored
- Publication bias can be identified
- Generate a pooled risk estimate
32
What is a meta-analysis?
- The use of statistical techniques in a systematic review to integrate the results of included studies.
- Calculate a weighted average of effects across all studies
- Generate a pooled risk estimate
33
What are the limitations of systematic reviews and meta-analysis?
- Publication bias
- Inconsistency of results
- Low study quality
- Heterogenity
34
When are systematic reviews used?
To make clinical decisions
35
What is public health?
The science and art of preventing disease, prolonging life, and promoting health through organised efforts of societies.
36
What are the domains of public health?
- Health improvement/promotion
- Health protection
- Health services/care
37
What is the main social determinant of health?
Life expectancy at birth
38
What is health promotion/health improvement?
- The process of enabling people to increase control over and improve their health
- Clinical interventions include screening and immunisation
- Knowledge transfer
- Healthy policies
- Community development
39
What is the tannahill model of health improvement?
- Prevention (medical interventions to reduce risk)
- Protection (legislation and social measures)
- Education (Influencing knowledge and attitudes)
40
What are the levels of prevention?
- Primordial (prevents emergence of unhealthy habits by not showing them in movies)
- Primary (Health promotion - vaccination, diets)
- Secondary (early detection and treatment)
- Tertiary (treating those already diagnosed, rehabilitation and quality of life action eg.smoking cessation)
41
What is the high risk approach to disease prevention vs the population approach?
- High risk is identifying those most in need and controlling exposure of a rare issue
- Population is recognising a common disease that affects society as a whole
42
What are the strengths and weaknesses of the high risk approach?
Strengths: Effective, effiecient, high benefit: risk ratio, approprite to the individual
Weakness: Palliative and temporary, limited potential, hard to change individual behaviours
43
What is the prevention paradox?
- High risk approach has a higher benefit for individals but a lower benefit for society
- Population has a low benefit for the individual but high for society
- Eg. Down syndrome risk increases with maternal age, but there is a greater benefit of screening younger mothers as there are higher pregnancy rates so a greater proportion of down syndrome babies are by younger moms.
44
What are the strengths and weaknesses of the population approach?
Strengths: Large potential for the population, behavourally appropriate, radical
Weaknesses: small advantage to the individual, low motivation for the physician and the patient, low benefit: risk ratio
45
What is basic research?
Reaearch looking at the scientific processes at a cellular level
46
What is applied research?
Research that takes place in a natural setting to see how the basic research is seen in the real world
47
What is empirical research?
Research that is purely evidence based, meant for a clinical setting
48
What is reductive research?
Research that looks at use of ath results outside of a clinical setting, ie. generalisation to areas that are not clinical. The aim may be to encourage patients to increase or decrease an exposure.
49
What is the validity of a test?
- The ability to distinguish between subjects with the condition and those without.
- Defined in terms of sensitivity and specificity
50
What is the gold standard?
A definite test to determine the disease status of individuals
51
What is sensitivity?
Ability of a test to correctly identify people with the disease
52
What is specificity?
The ability of the test to correctly identify people without the disease.
53
What is the positive predictive value?
The likelihood a patient with a positive test result will actually have the disease
54
What is the negative predictive value?
The likelihood a patient with a negative result will not have the disease.
55
What are receiver operator characteristics curves?
Curves used to determine a cut off value for a diagnostic or screening test.
56
What are the major approaches to screening?
- Mass screening involved the whole population
- Targeted screening involves groups who are anticipated to have an increased prevalence.
- Systematic screening is where people are called for screening.
- Opportunistic programmes are where the person goes to the doctor for another reason and are offered a test.
57
What is a clinical trial?
A planned experiment in humans to measure the effectiveness of an intervention.
58
How are experimental studies different to epidemiological studies?
Most epidemiological studies involve an investigator observing a group of people with no interference. Clinical trials involve interference.
59
List the main features of a clinical trail.
- They must contain a control group
- They must be prospective (participants are followed over time)
- Patients should be randomised
- There should be blinding
60
Why is a control group used?
- These are people who don’t receive the intervention. This is used to make sure we know why the outcome happened
- Control group receive a placebo or a standard treatment
61
Why does randomisation occur?
- People who are eligible for a trial are randomly allocated to the intervention or the control
- This removed allocation bias.
62
Why are trials blinded?
This ensures there is no measurement bias. People recieving a treatment may report improvement in subjective symptoms as they are enthusiastic, and doctors may also look harder for improvements.
63
How are trials regulated?
- They must be recorded by an independent scientific committee and approved by a research ethics committee.
- Trials use an independent data monitoring committee
- If there is a large difference they are able to stop the trial
64
How are clinical trials reported?
- According to the CONSORT (consolidated standards of reporting trials) guidelines.
- This ensures papers about trials include all the relevant information so readers can critically appraise them.
65
Why does epidemiological transition occur?
As a result of demographic, socioeconomic, technological, cultural, environmental and biological changes
66
Give examples of diseases that have appeared, disappeared and become more/less prevalent following epidemiological shift,
- Some diseases disappear (small pox) and others appear (AIDS) or re-emerge (TB,Dengue)
- There is a decline in stomach cancer, rise and fall of lung cancer and a shift from stroke to heart disease
67
What are the most commonly diagnosed cancers?
Lung, breast and colorectal
68
What are the most common causes of cancer death?
Lung, liver and stomach
69
What proportion of cancers are preventable?
ONE THIRD of cancers are likely to be preventable through a small number of lifestyle and environmental approaches
70
What is the largest preventable cause of cancer?
SMOKING is the largest preventable cause of cancer in the world
71
List the 9 major risks of cancer
- Smoking
- Low intake of fruit and veg
- Alcohol use
- Unsafe sex
- Overweight and obesity
- Physical inactivity
- Contaminated injections in healthcare
- Urban air pollution
- Indoor smoke from household solid fuel use
72
List some examples of cancer deaths due to infections
```
Hepatitis – liver
H. pylori – gastric cancer
HPV – cervical
EBV – Hodgkins lymphoma, stomach cancer
HIV - "AIDS-defining malignancies": Kaposi sarcoma, non-Hodgkin lymphoma, and cervical cancer.
Schistosomes – bladder cancer
```
73
Where do CHD and stroke rank in mortality worldwide?
1st CHD
| 2nd stroke
74
Where does CHD and stroke have a greater impact?
- More deaths in the developing world
- Low rates in japan
- High rates in europe and middle east
- Rates are higher in men
75
List the three main risk factors for CVD
- High blood pressure
- Tobacco smoking
- Cholesterol level
76
Where are infectious diseases the leading cause of death?
Sub-Saharan Africa
77
List the 6 commonest infectious causes of world mortality
1. Lower respiratory infections- 3.9M
2. HIV/AIDS-2.8M
3. Diarrheal diseases -1.8M
4. Tuberculosis- 1.6M
5. Malaria- 1.2M
6. Measles-0.6M
78
Define case
A person who has the disease, health disorder or suffers the event of interest
79
Define morbidity
Number of cases of ill health, complications, side effects attributed to a specific condition over a particular time period.
80
How is the AIDS epidemic controlled?
- Broad access to Anti-Retroviral Therapy
- Effective HIV prevention methods- Safer sex, safer injection practices, condom use and male circumcision
- Decline in HIV prevalence in pregnant women
- Now a vaccine is needed
81
How is the prevalence and mortality of HIV changing over time?
- The numbers of new cases of HIV being diagnosed each year (incidence) is rising.
- The numbers of deaths from AIDS has declined, due to improved treatment (HAART).
- The consequence is a steep increase in the prevalence of HIV (the number of people living with HIV).
82
List the major sources of routine data in the UK
- 2001 Census
- Health Survey for England
- NHS Inpatient Survey on patient experience
83
List the advantages of routine data
- Relatively cheap
- Already collected and available
- Standardised collection procedures
- Relatively comprehensive – population coverage, large numbers
- Wide range of recorded items
- Available for past years
84
List the disadvantages of routine data
- May not answer the question (no information or not enough detail)
- Incomplete ascertainment (not every case captured)
- Variable quality (e.g. variable diagnosis fields)
- Validity may be variable (i.e. do they measure what you think they measure?)
- Disease labelling may vary over time or by area
- Need careful interpretation
85
Define standardised mortality ratio
A ratio between the observed number of deaths in an study population and the number of deaths would be expected (accounting for age and often sex)
(observed deaths/ expected deaths)
86
Give an example of the use of standardised mortality ratio
Age Standardised Death Rates: Measuring how many people die each year and why they have died is one of the most important means of assessing the effectiveness of a country's health system.
87
Define a sample
- A group of people, objects, or items that are taken from a larger population for measurement.
- Estimates of the true underlying risk in a population can be calculated
88
Define variation
Variation of observations (the data points) in a single sample.
89
Describe how relative risk and odds ratio are interpreted
RR<1 exposure has lower risk than outcome
RR=1 Exposure is not associated with the outcome
RR>1 Exposure is associated with a higher risk of the outcome
90
What are the methods of controlling for confounding at the design stage?
- Randomisation (with minimisation to prevent the risk of allocation bias)
- Restriction/matching (in case control)
91
What are the methods of controlling for confounding at the analysis stage?
- Stratification (splitting analysis)
- Standardisation
- Regression
92
List the bradford hill criteria.
- Temporal relationship (only one that is necessary)
- Strength
- Consistency
- Specificity
- Dose-response relationship
- Plausibility
- Coherence
- Experimental evidence
- Analogy (a source of an elaborate hypothesis about the association in question)
93
List the phases of clinical trials
- Phase 1 (tests safety on a small number of healthy volunteers)
- Phase 2 (biological test to look at effectiveness using a few hundred people with the condition)
- Phase 3 (Overall effectiveness on thousands of patients, randomised control trial)
- Phase 4 (to look at rare side effects, post marketing)
94
Identify potential biases in clinical trials
- Allocation bias
- Measurement bias
- Reporting bias
- Sample size
95
Define the experimental event rate
Incidence in the intervention arm
96
Define the control event rate
Incidence in the control arm
97
Describe how to calculate relative risk in clinical trials
EER/CER
98
Describe how to calculate relative reduction in clinical trials
(CER-EER)/CER
99
Describe how to calculate absolute risk reduction in clinical trials
CER-EER
100
Define number needed to treat
- The number of people that must be treated to prevent one occurrence of the disease
- 1/ARR
101
List the critical appraisal guidelines for randomised control trials, observational studies, and systematic reviews
- RCT uses CONSORT
- Observational studies use STROBE
- Systematic reviews use PRISMA/MOOSE
102
Why are systematic reviews conducted?
- Due to the high volume of data that needs to be considered
| - Single studies are insufficient, with poor study design and low numbers
103
How is heterogenity identified?
Gailbriath plots - more appropriate to use meta-analysis when there is heterogenity
104
Why is screening performed?
- Early diagnosis of disease where early intervention improves prognosis
- Identification of high risk individuals where intervention improves prognosis
- Identification of those posing a risk to others
105
List the mass screening programmes in the UK
- Cervical Cancer - every 3 years for women aged 25-49, every 5 years to women 50-64
- Breast Cancer - every 3 years for women aged 50-70, women aged 70 and over can self-refer
- Bowel Cancer - every 2 years for men and women aged 60-74
- Abdominal Aortic Aneurysm - offered to men in their 65th year
- Diabetic Eye Screening - offered to people with type 1 or type 2 diabetes over the age of 12
106
List the criteria for screening programmes
- Feasibility
- Effectiveness (affected by selection bias, lead time bias, length time bias)
- Cost
- Ethics of screening
107
Define lead time bias
- Screening identifies disease that would be otherwise identified at a later stage
- Improvement in survival due to screening which is really due to the earlier date of diagnosis.
108
Define length time bias
- As some conditions may be slower in developing to a health threatening stage, they no longer have a preclinical stage.
- More likely to be detected at a stage that has a more favourable prognosis leading to the false conclusion that screening is beneficial in lengthening lives of those found positive.
