epi STATS Flashcards
How is the stomach cancer prevalence
decrease in stomach cancer
How the prevalence of lung cancer
rise and fall of lung cancer
from what to what disease has there been a shift
stroke to coronary heart diesease
How many world wide deaths were due to cardiovascular disease
15.6 million deaths worldwide in 2010
What are the main cardiovascular events
stroke and CHD
What percentage of total deaths were due to coronary heart disease
29.5% of all deaths in 2010
Where are cardiovascular problem more of an issue in the developing countries or in the developed countries
More such deaths occurred in the developing world than the developed world.
What are the rank first and second among cause-specific mortality worldwide?
CHD and Stroke respectively rank first and second among cause-specific mortality worldwide.
Where are the incidence of the lowest?
Japan, UK and western countries
Where is the CHD risk the highest ?
Middle east and former socialist economies
Are rates of CHD higher in men or in women
men
When are the risks of CHD the highest in females
post menopause
What is the overalll trend in the world of CHD and strokes and which countries do not follow this trend
On the decline in all other countries
Rise in CHD and stroke mortality in the formerly socialist economies of Europe and South Asia.
What percentage of death is caused by cancer in many countries
more than 25% of deaths in many countries
what percentage of deaths is caused by cancer worldwide
15.1% of deaths worldwide in 2010
How many people died of cancer in 2010
8 millions people dies of cancer in 2010
How many percent of
deadly cancers occur in less developed countries
60% of these cases are likely to occur in less developed countries
most commonly diagnosed
Lung
Breast
Colorectal
Most commonly died from cancer
Lung
Liver
Stomach
Does cancer risk chnage when migrants change from country to country
Cancer rates in migrants converge towards local cancer rates over time - role for modifiable risk factors
How many cancers are preventable
1/3
What is the largest preventable cause of cancer
SMOCKING
MAJOR KNOWN CARCINOGENS:
Tobacco
Alcohol
Air Pollution
Occupational Agents
What is the prevalence?
Prevalence = the frequency of a disease in a population at a point in time
Hence it is often called point prevalence
What measurment can be interpreted as a probability?
he measure of incidence can be interpreted as the probability, or risk, that an individual will develop the disease during a specific time period.
Successes for the AIDS epidemic
Decline in HIV prevalence in pregnant women
HIV Prevention:
Safer sex
Safer injection practices
Condom use
Male circumcision
For every how many people treated for HIV how many are newly infected
For every person put on HIV treatment, FIVE are newly infected with HIV.
how many people die each year?
57 million
Standardiesed mortality ration
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.
What is the leading cuase of death in subsahran africa
INFECTIOUS DISEASES ARE THE LEADING CAUSE OF DEATH IN SUB-SAHARAN AFRICA
what are the top causes of infectious diseases in the wolrd? What is the percentage of people dyingfrom these top theses infectious in comparison to all other infectious diseases?
Epidemiology of Infectious Diseases
MORE THAN 90% OF DEATHS FROM INFECTIOUS DISEASES ARE CAUSED BY:
Lower respiratory infections
HIV/AIDS
Diarrhoeal Diseases
Tuberculosis
Malaria
Measles
What country has the highest death rate? What countries follow it ?
Swaziland
Angola, Lesotho, Sierra Leone and Zambia.
Leading causes of death
Heart Disease
Cerebro-Vascular Disease
Respiratory Infections
HIV/AIDS
COPD
What is morbidity and how is it expressed
Morbidity - the number of cases of ill health, complications, side effects attributed to a particular condition over a particular time period
How many deaths in third world countries are due to malnutrietion
58%
Hierachy of evidence
Hierarchy of Studies
Systematic reviews and meta-analyses
Randomised Control Trials
Cohort Studies
Case-Control Studies
Cross-sectional Studies
Case Series
Case Reports
Definition of Bias
Bias = a systematic error in design, conduct or analysis of a study which produces a mistaken estimate of treatment effect.
definition of Confounding
= when a variable (or factor) is related to both the study variable and the outcome so the effect of the study variable on the outcome is distorted.
Experiment design ? What single type of studz does it include? What does it test?
A planned experiment in humans.
Designed to measure the effectiveness of an intervention:
A new drug
A surgical procedure
A vaccine
Complementary therapy
What are observational studies
Don’t influence the exposure cohort study, case control, ect…
What has to be in a clinical trial
Features of a Clinical Trial
Define your intervention
Define your comparator:
Placebo
Alternative treatment
Standard of care
Define your inclusion criteria
Define your exclusion criteria
Describe the 4 phases of randomized control trial
Phases of Clinical Trials
Phase I
Test the safety of a new treatment
Small number of, usually healthy, volunteers
Phase II
Test to see if the treatment is efficacious - at least in the short term
Continue to look at safety
A few hundred people usually with the condition
Phase III
Compare the new treatment with the current or placebo
Look at how well the new treatment works (effectiveness)
Continue to monitor side effects
Several thousand patients
Phase IV
After the drug has been marketed
Measure effect in various populations
Look out for rare side effects
Control Event Rate (CER)
incidence in the control arm
Experimental Event Rate (EER)
Experimental Event Rate (EER) - incidence in the intervention arm
Absolute Risk Reduction
Absolute Risk Reduction (ARR) = CER - EER
Relative Risk Reduction (RRR)
= ARR/CER
Number Needed to Treat (NNT)
Number Needed to Treat (NNT) - number of patients that need to be treated for one to get benefit
1/ARR
How to know the Sample Size needed for a trial
Prospective Power Calculation
How to eliminate allocation bias?
Randomisation
Ensured balance and eliminates bias.
Avoids bias in treatment allocation
Methods of Randomising:
Block Randomisation - assign people to group A or group B randomly
Stratification - done by centre - can be divided by important patient characteristics e.g. male/female
Minimisation - adaptive stratification - calculates imbalance and allocates to maintain balance
how to eliminate measurement bias
Minimising Measurement Bias
Blinding - single, double, triple
Endpoint Selection
Objective/Subjective
Accurate and Precise
Consistent and Repeatable
Primary/Secondary/Tertiary end points
Loss to Follow-up
Missing data
Different between groups
Intention-to-treat analysis
What are the descriptive studies
ndividuals - case reports, case series, cross-sectional studies
Populations - ecological studies
What are the analytical studies
Observational: case control, cohort
Experimental: clinical control trial
What gets measured in a cohort study
relative risk
What get calculated in a case control study
odds ratio
Measures how to asses exposure in case control study
Self-Reported
Measured in clinic (e.g. BMI)
Existing Records (e.g. medical/pharmacy records)
Measurment outcome can be….?
inary Outcome
With or without the disease of interest
Continuous Outcome
E.g. blood pressure
Can use an arbitrary cut point
Advantages and disadvantages of cohort studies
Avantages: - look at multiple outcomes - good for rare exposures - allows the calculation of relative risk - calculation of incidence - temporal relationship - minimise biases - no ethical consideration Disadvantages: - long follow up periods - expensive time consuming - loss to follow up might introduce bias - Healthy worker effect - not for rare diseases
Case control study, advantages and disadvantages
Advantages: - good to look at rare diseases - good to look a multiple risk factors - cheap - quick - calculate odds risk Disadvantages - can not calculate incidence - bias in exposure assessment (recall bias) - lack of temporal relationship]
Measurement errors in case control study
Measurement Error in Case-Control Studies
Recall Bias
Patients with the disease may be more inclined to answer questions carefully - may have a distorted view of exposure
Interviewer Bias
If the interviewer knows who has the disease, they may be more inclined to over-report exposures known to be associated with the disease of interest
Outcome Bias
Diagnostic bias
EXAMPLE: women taking menopausal hormone therapy may be screened for breast cancer more regularly
Examples of cross sectional studies
Health Survey for England
2001, 2011 Census
National Survey of NHS Patients
Advantages of routine data
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
Experience in use an interpretation
Disadvantagfes of routine data
Disadvantaged of Routine Data
May not answer the question (not enough detail)
Incomplete ascertainment (not every case captured)
Variable quality
Validity may be variable
Disease labelling may vary over time or by area
Coding changes could create artefactual increases or decreases in rates
Need careful interpretation
Types of routine data
Types of Routine Data
Health outcome data (e.g. deaths, hospital admissions, primary care consultations or prescriptions)
Exposure and health determinant data (e.g. smoking, air pollution, crime statistics)
Disease prevention data (e.g. screening and immunisation uptake)
Demographic data (e.g. census population counts)
Geographical data (e.g. health authority boundaries, location of GP practices)
Health service provision (e.g. bed/staff counts)
Most commonly
Breast
Lung
Large Bowel
Prostate
Bladder
Why are single studies unreliable
Poor study design or small numbers - low power - false-negative results
Study will often only look at one subset of the potential study population
Stages of planning a systematic review
Stage I: Planning a Review
Specify the question to be addressed
Usually framed around PICOS:
Population
Intervention/Comparison
Outcomes
Study Design
Stage II: Conducting the Review
Identification of Research
Clearly defined search criteria
Search published medical literature
Search other sources
Missing Studies = BIAS
Selection of Research
Study Quality Assessment
META-ANALYSIS
The use of statistical techniques in a systematic review to integrate the results of included studies.
Stage III: Reporting and Dissemination
Study details tabulated in a meaningful way
Should include details of PICOS
Issues in systematic reviews and meta analysis
Issues in Systematic Reviews and Meta-Analyses
Publication bias
Inconsistency of results
Low study quality
NOTE: Null or non-significant findings are less likely to be reported/published than statistically significant findings
This BIAS may distort meta-analyses and systematic reviews
Inconsistency of Results
Different PICOS
Advantages of meta analysis
Generate a pooled overall risk estimate
Produce a more reliable and precise estimate of effect
Explore differences (heterogeneity) between published studies
Identify whether publication bias is occuring
Does alcohol consumption decrease or increase with social class
lcohol consumption decreases with socioeconomic class
Does obesity increase or decrease with deprivation
Obesity increases as deprivation increases
Does smocking decrease with age? IN some social classes when is the peak age?
Smoking generally decreases with age though in some socioeconomic classes there is a peak around 45-54 years
What is used to treat schistosomiasis
praziquantel
What is used to treat helminths?
Albendozol
What is used to lymphatic Filariasis
Albendozol
What else is used to treat helminths
Mebendazol
What is used to treat onchocerchiasis
Mectizan
What is used to treat trachoma
Zithromax
What are the Protozoa infections
Chagas, leishmenias, trypanosomiasis
What are the helminth infections
Lymphatic filariasis, Schistosmiasis, Onchociriasis,
What are bacterial infection
leperosy, buroliosa, trauchoma,
What is the host in schistosomiasis
snail
what iss the host in onchoceriasis
Blacklfly
what is the host in lymphatic filariasis
Mosquito
What are the soil helminths
Hookworm, trichuriasis, ascarias
Three key policy documents
Ottawa Charter
Jakarta Declaration
Bangkok Charter
Tannahill prevention module
Prevention
Health Education
Health Protection (legal, fiscal)
Current public health initiatives
Smoking Cessation
Alcohol Harm Reduction Strategy
Tackling Obesity - Change for Life
Sexual Health - National Chlamydia Screening Programme
Tackling Teenage Pregnancy
Vaccination Programmes
Bradfort hill criteria
TAPED SSCC
Strength - a small association does not mean that there is no causal relationship
Consistency
Specificity - the more specific the association between a factor and an effect, the bigger the probability of a causal relationship
TEMPORALITY - exposure has to occur before the event
Dose-Response Relationship - greater exposure should generally lead to greater incidence
Plausibility
Coherence - between epidemiological and laboratory findings
Experiment
Analogy - the effect of similar factors may be considered
What is the critical appraisal checklist for randomised control trails
consort
what the is the checklist for observational studies
STROBE
Checklist for meta analysis
MOOSE
Checklist for Systematic reviews
PRISMA
Statistical association due to
Chance
Bias
Confounding
Cause
Control confounding factors
Design Stage:
Restriction (all about inclusion and exclusion criteria)
Randomisation
Analysis Stage:
Stratification (risks are calculated separately for each category of confounding variable)
Standardisation
Regression
GRaphs used in systematic reviews and meta analysis
Galbraith (Radial) Plot - heterogeneity in results
Funnel Plot - publication bias
Forest Plot - showing all the results of the individual studies and the overall result of the meta-analysis (diamond)
Cervical cancer screening
every 3 years for women aged 25-49, every 5 years to women 50-64
Breast cancer screening
Breast Cancer - every 3 years for women aged 50-70, women aged 70 and over can self-refe
Bowel cancer
Bowel Cancer - every 2 years for men and women aged 60-74
Abdominal aortic aneurysm
- offered to men in their 65th year
Diabetics eye
Diabetic Eye Screening - offered to people with type 1 or type 2 diabetes over the age of 12
Cervical cancer mortality has …
decreased
breast cancer mortality has
decreased
incidence of cervical cancer
stays same
Cox regression
Cox Regression - considers whether the effect of a treatment has a multiplicative effect on the subject’s hazard rate (e.g. taking a statin may halve our immediate probability of having a MI)
Hazard Ratio
Hazard Ratio - the effect of an explanatory variable on the risk of an event
What tropical diseases do not cause death?
Hookworm, lymphatic filariasis, onchiocerciasis, trachoma
What is the ntd which causes the most amount of DALY? what is the number?
Lymphatic filariasis
HOw many people die every year of schistosomiasis?
41000
How many people die of leprosy?
5000
What is the neglected tropical disease with the most deaths? What is the number?
Leishmaniasis 47000
