1.1. Population Data - Epidemiology, Incidence, Prevalence, and Risk Flashcards
What does the study of “Epidemiology” look at?
It looks at the nature and type of illness in society (using the numerical science of epidemiology) by looking at the time, place and person affected
E.g. rate of occurrence of heart disease between 18th century English Women and 20th century Finish Men
What is the most recent example of an Epidemiological Study
Cholera Epidemic in Haiti, 2011
What are the 3 main aims of Epidemiology?
- Description
- Explanation
- Disease Control
What does the “Description” aspect of Epidemiology entail?
Describing the amount and distribution of disease in human populations
- What does the “Explanation” aspect of Epidemiology entail?
- How does this happen?
- To elucidate the natural history, and identify aetiological factors for the disease
- By combining Epidemiological data with data from other disciplines
What does the “Disease Control” aspect of Epidemiology entail?
Providing the basis on which preventative measures, public health practices, and therapeutic measures can be developed, implemented, monitored and evaluated
What is compared in Epidemiology?
Study Populations
What may define the “Study Population”, being compared in Epidemiology?
- Age
- Sex
- Location
- (The same group over) Time
In comparing “Study Populations”, what is this used to detect?
- Aetiological clues (what causes the problem)
- The scope for prevention
- The identification of high risk or priority groups in society
- What does “Clinical Medicine” deal with?
2. What does “Epidemiology” deal with?
- The individual patient
- Populations
Note - it is essential to be clear about which populations are being talked about when studies / surveys / formulation of hypotheses are being carried out
What is used to be clear about the risk to a population?
Ratios (expressed in terms of a specified time period, and national “at risk” population)
- What is the ratio used to express risk in a population?
2. Use an example of Deaths from IHD in men aged 55-64 in Grampian in 1990:
- Number of Events / Population at Risk
2: Deaths from IHS in men aged 55-64 in Grampian in 1990 /
All men aged 55-64 in Grampian in 1990
What are the ratios, used to express risk in a population, often converted into?
- Rates, by expressing them in terms of a specified time period (e.g. per year)
- A notional “at risk” population in “X per 1000; per 10000…”
What is the significance of the “at risk” part of the ratio, used to express risk in a population?
- Everyone in the denominator (total populous studied) must have the possibility of entering the numerator (those with the condition)
- All those people in the numerator (those with the condition) have come from the denominator (total populous studies)
What is the definition of “Incidence”?
The number of new cases of a disease in a population in a specified period of time
What is the definition of “Prevalence”?
The number of people in a population with a specific disease at a single time, or in a defined period of time
Will minor illnesses (e.g. a cold) have a high or low incidence?
High
Will minor illnesses (e.g. a cold) have a high or low prevalence?
Low
Will a chronic illness (e.g. diabetes) have a high or low incidence?
Low
Will a chronic illness (e.g. diabetes) have a high or low prevalence?
High
What does “Incidence” tell us about?
- Trends in causation
2. Aetiology of the disease
What does “Prevalence” tell us about?
- The amount of the disease in the population
2. The workload for the NHS
Is “Prevalence” useful in studying the causes of the disease?
No
What is “Prevalence” of chronic conditions dependent on?
- Number of the populous developing the disease
- Number of the populous living with / recovering from the disease
- Number of the populous dying from the disease
What is “Relative Risk”?
The measure of the strength of an association between:
- A suspected risk factor
- The disease under study
What is the ratio for “Relative Risk”?
Incidence of disease in Exposed group /
Incidence of disease in Unexposed group
What would the “Relative Risk” be; of lung cancer in people smoking 25+ per day, compared with non-smokers?
(Show working)
Incidence of Lung Cancer in smokers of 25+ per day / Incidence of Lung Cancer in non-smokers = (251/1000) / (10/1000) = 25
What would the “Relative Risk” be; of lung cancer in people smoking 25+ per day, compared with people smoking 1-14 per day?
Incidence of Lung Cancer in smokers of 25+ per day /
Incidence of Lung Cancer in smokers of 1-14 per day
=
(251/1000) / (78/1000)
=
3.22
Other than lung cancer, what is a common relative risk?
- Risk of DVT with Oral Contraceptive Pill
2. Vaccination and Complication
What is the Number of women at risk of DVT, in relation to generation of Oral Contraceptive Pill and Pregnancy?
Increases going down: 1. Normal (5/100,000) 2. 2nd Generation OCP (15/100,000) 3. 3rd Generation OCP (25/100,000) 4. Pregnancy (60/100,000) Note - this relates to Relative Risk
What are the different levels of Risk?
- Risk Massive (1/1 - 1/10)
- Risk rapidly increasing (1/100 - 1/10,000)
- “Home Base” (1/100,000 - 1/1,000,000)
- Risk Remote (1/10,000,000 - 1/100,000,000)
- Risk rapidly decreasing (1/100,000,000 - 1/1,000,000,000)
- Minuscule Risk (1/10,000,000,000 - 1/1,000,000,000,000)
What are the sources of Epidemiological Data?
- Mortality data
- Hospitality Activity Statistics
- Reproductive Health Statistics
- Cancer Statistics
- Accident Statistics
- General Practice Morbidity Statistics
- Health and Household Surveys
- Social Security Statistics
- Drug Misuse Statistics
- Expenditure data from the NHS
