Health and Disease in Populations Flashcards
What are censuses useful for? (3 things)
- allocating resources
- projecting populations
- observing trends in populations, e.g. Age and ethnicity
What is CBR?
Crude Birth Rate- number of live births per 1000 people
What is GFR?
General Fertility Rate- number of live births per 1000 women aged 15-44
What is TPFR?
Total Period Fertility Rate- average number of children born to a hypothetical woman in her life time.
What is the advantage of using TPFR
It isn’t influenced by age group structure
What is CDR?
Crude Death Rate- number of deaths per 1000 people
What is ASDR?
Age specific death rate- number of deaths per 1000 in age group.
What is SMR?
Standardised Mortality Rate - compares observed with expected values, adjusts for age-sex distributions and other confounders
Define incidence rate
The number of new cases of a disease per 1000 people per year
Define prevalence
The amount of people in a population who have a specific disease
What is IRR?
Incidence Rate Ratio - compares incidence rates of two populations with varying exposures, so relative risk can be calculated.
Define ‘confounding factor’
Something that is associated with both outcome and exposure, but is not part of the causal pathway
Why do we produce error factors and confidence intervals?
To account for variation
What is a P Value?
The probability of obtaining a test statistic
What is biasing?
The deviation of results from the truth via a certain process
What is selection bias? Give two examples.
Error due to the two groups being collected in a way with systematic differences , e.g. Allocation bias or healthy worker effect.
What is information bias? Give two examples.
Error due to systematic misclassification of subjects in the group e.g. Recall bias and publication bias.
What is a cohort study?
Recruitment of disease free individuals, classifying them according to their potential exposure and following them up for extend periods.
What kind of situations are cohort studies good for studying? (Two things)
Rare exposures and diseases which take a long time to develop.
What are the two main types of cohort study?
Prospective
Retrospective
What is the difference between internal and external comparisons?
Internal - compare sub cohorts who are either exposed or unexposed, calculate IRR
External- compare exposed with external reference population, calculate SMR
What 5 things must you write when evaluating a study in a exam question?
Can we reject the null hypothesis? State the p value State if H0 is with in the CI Are the results statistically significant? How many times more at risk?
What are case control studies?
Recruit disease free individuals and diseased individuals, then determining their exposure status. Then calculate an odds ratio.
How do you calculate an Odds Ratio?
(AxD/BxC) ( where cases and Controls are alphabetically across the top of the table, exposed and unexposed are alphabetically across the left of the table and the boxes are lettered a to d left to write and top to bottom)
What is the null hypothesis for a case control study?
1
What situation is a case control study good for?
Rare exposures
Would you normally have more cases or controls in a case control study?
More controls, (usually 5x more) because controls are easier to find and the greater number of people helps reduce the error factor.
What is a RTC?
Randomised control trials are experimental studies which involve patients who are recruited and allocated randomly to either treatment. Patients are followed up in identical ways.
Why would you use placebos in a RTC?
Remove the placebo affect
What is meant by intention-to-treat
Outcomes of RTCs include non-compilers as this represents how the public might respond to the treatment.
What are the Bradford Hill criteria? (9 things)
Strength of association
Specifity of association
Consistency of association with other studies
Temporal sequence, dose cause precede outcome?
Dose response, do different levels of exposure lead to different levels of outcome?
Reversibility, does removal of cause reduce outcome risk?
Biological plausibility, is there a mechanism to support the theory?
Coherence of theory, observation conforms with current knowledge?
Analogy, does another similar cause have a similar outcome?
How can you minimise losses? (3 things)
Make follow up appointments at convenient times
Use no coercion or inducements
Be honest with the patient
How can compliance be maximised? (3 things)
Give simple instructions
Allow the patient to ask questions
Make the treatment simple and accessible for the patient
What are the main ethical concerns associated with RTC? (5 things)
You can’t give a patient a treatment you know to be less effective
Pursuit of knowledge must be for the good of the population
Recruitment mustn’t unfairly exclude anyone
Participants must have given consent, with cooling off period and ability to drop out
No coercion or manipulation
What are systematic reviews?
Compilations of many primary studies, mainly RTCs, some cohort and control studies
What is meta analysis
Quantitative synthesis of data from many studies giving an overall value with CIs
Describe the two effect models used in systematic reviews
Fixed effects model- assumes homogeneity variation from with a study
Random effects model- assumes heterogeneity, variation from within and between the studies
What can be determined from a funnel plot, what pattern will be produced?
Determine publication bias - where only statistically significant studies are published. Plot odds ratio against study size - should produce an inverted funnel shape.
What are the benefits of systematic reviews?
Reduce bias and exclude poor studies.
Meta analysis provides an overall figure
Large amounts of information can be assimilated quickly, reducing time between discovery and implementation
Used in evidence based practice guidelines
Define Census
Simultaneous recording of demographic data of all persons in a defined area carried out by a government.
