Epidemiology Flashcards
Define public health and list its main domains (3 domains)
The science and art of preventing disease, prolonging life and promoting health through organized efforts of society.
Focused on populations.
Main domains:
- Health protection
- Health improvement
- Quality of healthcare
Explain the distribution of risk factors in the population
Distribution of risk factors depends on the structure of the population and the disease. Example risk factors which can vary in distribution between populations:
- Age
- Sex
- Socioeconomic
- Prevention of disease and treatment strategies
- Access to healthcare
Explain the difference between high-risk strategy and population-based strategy
High risk strategy targets individuals who are considered high risk for disease.
Population-based strategy targets entire populations regardless of individual’s risk factors.
Define the term epidemiology
Major academic discipline of public health; focused on health and disease in the population.
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.
Describe how to quantify disease in population using the following:
- Incidence
Describe how to quantify disease in population using the following:
- Prevalence (point and period)
Describe how to quantify disease in population using the following:
- Mortality, Survival and Case-fatality
Describe the measures used to compare disease rates between populations, including:
- Gender
- Age standardisation (direct and indirect)
Disease burden varies by sex and age.
% of different sex/age groups vary across populations and in the same population over time.
Rates used to compare populations:
- Sex-specific
- Standardized for different age structure using a reference population:
- Standardized mortality ratios:
- Observed n of deaths / Expected n of deaths x 10n
- Age standardized rates
- Standardized mortality ratios:
Age standardization
- Direct
- Common age-structured population used as standard
- European standardized rates
- Indirect
- Age-specific rates unavailable
- Common set of age-specific rates is applied to the populations whose rates are to be standardized
Define and describe the epidemiological basis for prevention strategies, including:
- Primary prevention
- Secondary prevention
- Tertiary prevention
Describe primordial prevention
Primordial prevention:
- Actions that inhibit future emergence of risk factors known to increase risk of disease, to minimized hazards to health.
- Prevent health impact on foetus
- Parental education on epigenetic influences of child
- Parental support
- Asbestos – PPE vs substitution vs ban
Describe two approaches to prevention
Two approaches to prevention:
- Target populations (whether exposed to risk factors or not); e.g. water fluoridation
- issues with population approach is that quite a lot of people who do not have a risk factor do not benefit from the intervention, yet will still be exposed to the risks of that intervention. Areas of deprivation may not be able to benefit (e.g. water fluoridation not available everywhere) so may create health inequity across the population.
- Target individuals; e.g. screen smokers for premalignant oral lesions
Define and categorise modifiable risk factors
Risk = probability of harm from hazard × severity of outcome
Risk factor: any attribute, characteristic or exposure of an individual that increase the likelihood of developing a disease of injury
Modifiable risk factor: a risk factor which effect can be reduced by intervention
Categories of modifiable risk factors:
- Lifestyle; environmental; socio-economic; psychological; wider societal.
Recall the wider determinants of health
Differentiate between the concepts of association and causation
Association: statistical relationship between a risk factor and a disease
Causation: exposure to a risk factor leads to disease
Association does not always mean causation; association does not necessarily mean risk.
List the Bradford Hill Criteria (9 points)
Bradford Hill Criteria (9 points):
“_S_ome _C_anadians _S_ay _T_hat _B_uying Big _C_ars _E_xcites _A_mericans”
- Strength of association – the stronger the association, the less likely it is due to chance
- Consistency of the observed association – has it been observed in different places, by different people?
- Specificity – if limited to specific persons, sites and types of disease, the relationship supports causation
- Temporality – time between exposure and outcome must be consistent with proposed mechanism
- Biologic gradient – dose-response relationship
- Biologic plausibility – proposed mechanism by which exposure might reasonably alter risk of disease
- Coherence – the observed data should not conflict with known facts about the Hx/biology of the disease
- Experiment – support for causation may be gained through controlled experiments/trials
- Analogy – sometimes fair to judge cause-effect relationship by analogy (e.g. thalidomide) for new drugs.
Define measures of association, including:
- Risk
- Relative risk
- Risk difference
List the three types of study designs and give examples for each
Types of study designs with examples:
- Descriptive
- Case reports, case-series
- Ecologic
- Cross-sectional
- Analytic
- Case-control
- Cohort/follow up
- Experimental
- Clinical trials
- Uncontrolled
- Controlled (non-randomized vs randomized; not blinded vs blinded)
- Field trials
- Clinical trials
Describe the characteristics of an intervention study such as the Randomised Control Trial (RCT)
Experimental design – e.g. randomized control trial (RCT)
In a RCT, the only expected difference between the intervention and control is the outcome.
List the advantages and disadvtanges of a RCT
RCT advantages:
- Eliminates selection bias (use independent randomization system)
- Reduces confounding
- Easier to blind than observational studies
- Populations of participating individuals are clearly identified
- Basis of test of statistical inference
RCT disadvantages:
- Expensive in terms of time and money
- Volunteer bias – population who volunteer may not be representative of wider population
- Loss to follow-up attributed to treatment
- Need to have large enough sample size to reflect outcome of interest in representative population
Recall the RCT outcomes (including type 1 and type 2 errors)
Define P value and confidence interval (CI)
P-value:
- P = 0.5 – there is a 50% probability that the result was obtained by chance
- Normally set at P < 0.05 to accept that result was not obtained by chance
Confidence interval (CI):
- Measure of the precision of the estimate
- Set at 95% – there is a 95% probability that the true result lies within the CI
- CI will, after infinite repetitions of trial, contain the true parameter with a frequency no less than its CI
- If the CI range crosses 1, then not statistically significant
Recall the hierarchy of evidences (6 levels of the hierarchy pyramid)
Discuss the epidemiology of oral cancer (6 factors)
Risk factors for oral cancer:
- Tobacco - compared to non-smokers:
- RR 1.7 (70% increased risk) of oral cancers in males
- RR 1.55 (55% increased risk) in females
- (Parkin D British Journal of Cancer (2011) 105, S6–S13)
- Alcohol - compared to non-drinkers:
- RR 1.17 in those drinking one or fewer units per day
- RR 3.50 in those drinking more than 4 units per day
- (Turati F et al. Oral Oncol. 2010 Oct;46(10):720-6)
- Betel Quid – increased risk of oral cancer in British Asians
- Diet – fruit and vegetables – increased intake reduces risk by half
- ? Association of lifestyle with smoking and alcohol
- Human Papillomavirus - HPV 16 and 18
- estimated 8% of oral cancers
- estimated RR 4 in those with oral HPV vs those without
- (Syrjanen S et al. Oral Dis. 2011 Apr;17 Suppl 1:58-72)
- Sun – outdoor workers – cancer of the lip
