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Epidemiology > Introduction > Flashcards

Introduction Flashcards

1
Q

what is epidemiology?

A

study of patterns causes and effects of health and disease in defined populations
it informs our public health, policy, evidence-based practice - identifying risk factors and interventions for prevention

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2
Q

why is epidemiology important?

A

understanding risks, used for designing public health interventions, underpins much of evidence-based medicine

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3
Q

outline cholera

A

John snow
higher death rates in 2 areas supplied by same water company
identified pump on Broad street as cause of epidemic
used chlorine to clean handle and ended the outbreak

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4
Q

outline the smoking ‘british doctors study’

A

prospective cohort study by medical research council
1951- wrote to UK physicians
40,000 responded, males
statistical evidence linking smoking to lung cancer

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5
Q

outline AIDS epidemic 1980s

A

cohort study 1993 Schechter
followed 715 gay men for 8.6 years
all 126 AIDS cases only occurred in those 365 individuals with pre-existing HIV-1 antibody and CD4 counts fell - changed beliefs on aetiology
HIV-1 is involved in AIDS pathogenesis

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6
Q

outline the Northern Region Young Persons Malignant Disease Registry

A

cancer registry
all cases of cancer diagnosed in those 0-24 years from 1968-today
population based - cases from defined geographical region and time

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7
Q

what has the northern region young persons maligant disease registry shown

A

improved survival for children and young people with cancer
seasonal variation - indicates a role for environmental factors in aetiology
socio-economic disparities in survival

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8
Q

how can we measure disease frequency

A

incidence rate
prevalence rate
mortality rate
relative risk
rate ratio
standardised morbidity ratio
odds ratio

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9
Q

what are the 4 main study designs

A

case-control studies
cohort studies
cross-sectional studies
ecological studies

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10
Q

what is the definition of bias

A

any systematic error in epidemiological study resulting in incorrect estimate of association between exposure and risk of disease
selection bias/misclassification bias

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11
Q

what is the definiton of confounding

A

function of the complex interrelationships between various exposures and disease

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12
Q

what is genetic epidemiology

A

study of role of genetic factors in determining health and disease in families and populations
gene-environment interactions

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13
Q

what are the types of genetic study design

A

familial aggregation studies
segregation studies
linkage studies
association studies

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14
Q

what are family aggregation studies

A

find out if there is a genetic component and what the relative contributions of the genes and environment are

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15
Q

what are segregation studies in genetic epidemiology

A

find out the pattern of inheritance of disease (dominant or recessive)

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16
Q

what are linkage studies in genetic epidemiology

A

find out which part of the chromosome the disease gene is located

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17
Q

what are association studies within genetic epidemiology

A

find out which allele of which gene is associated with the disease

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18
Q

what is the recent thing in genetic epidemiology

A

genome-wide association studies - lead to the discovery of many genetic polymorphisms that influence risk of developing common diseases

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19
Q

what is life course epidemiology

A

study of antecedant exposures and later health outcomes
take into account pathways between the two and evolution of health disorders over time
used to study long term effects on chronic disease and risk of exposure during gestation, childhood, adolescence and later life

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20
Q

what is perinatal epidemiology

A

period immediately before or after birth
congenital anomalies in children - aetiology and survival
reproductive loss

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21
Q

what is the prevalence of cancer

A

approx 1 in 2 people will be diagnosed with cancer at some point in their lives
risk increases in people 50+

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22
Q

what diseases does obesity increase the likelihood of

A

BMI > 30
heart disease
type 2 diabetes
obstructive sleep apnea
certain cancers
osteoarthiritis

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23
Q

outline the Newcastle 85+ study

A

out of those ages 85+ years no one was disease free and on average each person has 4-5 conditions

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24
Q

what are the methods used to investigate infections

A

outbreak investigation
disease surveillance
case-control studies
cohort studies
molecular epidemiology
vaccine assessments

25
Q

what is the definition of health inequality

A

differences in health status or distribution of health determinants between different populations

26
Q

what did the study of melanoma by McNally 2014 show

A

incidence and survival in young people in northern england
found increased risk of melanoma was linked to greater affluence but worse survival associated with living in a more deprived area

27
Q

what is incidence rate used to measure

A

measure and compare disease frequency in populations
good because rates adjust for population size

28
Q

what is the definition of incidence rate

A

number of new cases of a specified disease per population at risk in a given time period

29
Q

how is incidence rate calculated

A

(new cases occuring in given time period) / (population at risk during same time period)

30
Q

what should the numerator of the incidence rate equation not include

A

cases occurred/diagnosed earlier or later than the given time period

31
Q

what does the denominator of the incidence rate equation represent

A

the population from which the cases in the numerator arose from

32
Q

what is incidence rate specific for

A

age and sex
females and males are calculated separately
age calculated by 5 year group

33
Q

what must be ensured when calculating age/sex specific incidence

A

complete ascertainment of cases for a prescribed geographical area e.g country, county, district, ward

34
Q

what is the crude incidence rate

A

calculated as total number of cases / total population in the period

35
Q

what does the crude incidence rate not take into account?

A

the age structure of the population and cannot be used for comparison with other populations/countries

36
Q

what is an example of when crude incidence rate did not work

A

2 australian health surveys examined circulatory system health problems in general population and indigenous population in each age group over 24 years, indigenous had higher rates but crude incidence showed general as higher because the median age of indigenous was 21 and median age of general was 37

37
Q

how do we overcome the problem of comparing populations with different age structures?

A

weighting
rates are weighted to a standard population e.g WHO
AGE-STANDARDISED INCIDENCE RATE

38
Q

so how is age standardised incidence rate calculated

A

summary of individual age-specific rates using external population standard
d(i) / y (i) = age specific rate for i category

39
Q

what is prevalence

A

frequency of existing cases
how much of a particular disease is present in a defined population

40
Q

so what is the difference between the numerators of incidence and prevalence

A

indice numerator is new cases in given time period
prevalence numerator is all cases present during given time period irrespective of when disease started
both new and old cases

41
Q

what is the equation for prevalence rate

A

(persons with given disease/condition during specified time period) / (population during same time period)

42
Q

what is mortality rate

A

probability/risk of dying in population over a period of time
frequency with which new death occurs in population over period of time

43
Q

what are some other types of mortality rate

A

perinatal mortality rate - neonatal death and stillbirth
maternal mortality rate - 15-44yrs
infant mortality rate -<1yr
child mortality rate <5 yrs

44
Q

what is relative risk

A

measure of disease frequency by calculating ratios - risk ratio and rate ratio
measures the strength of an association

45
Q

what is the risk ratio equation

A

risk (cumulative incidence) in exposed group / risk in unexposed group

46
Q

what is rate ratio equation

A

incidence rate in exposed group / incidence rate in unexposed group

47
Q

what is the odds ratio

A

odds of disease in exposed group / odds of disease in unexposed group

48
Q

what does the rate ratio do

A

compares 2 groups in terms or incidence/mortality rate
the two groups differ by demographic or exposure
rate ratio = rate for group of interest / rate for comparison group

49
Q

what does a rate ratio of 1 mean

A

identical risk in the 2 groups

50
Q

what does a rate ratio of > 1 mean

A

increased risk for numerator group

51
Q

what does a rate ratio of < 1 mean

A

increased risk for denominator group

52
Q

what is the odds ratio definition

A

estimate of risk from case-control studies
measure of association - quantifies relationship between exposure and health outcome from comparative study (case-control study)

53
Q

what is the equation for odds ratio - case control studies

A

odd ratio = (a x d) / (b x c)

54
Q

what is the abcd of the odds ratio equation

A

a = ppl with disease and exposure of interest
b = ppl without disease but with exposure of interest
c = ppl with disease but without exposure of interest
d = ppl without disease or exposure of interest

55
Q

and is a+c and what is B+D

A

ac = cases
bd = controls

56
Q

what is the standard mortality ratio equation

A

SMR = observed cases / expected cases x 100

57
Q

outline standard morbidity ratio

A

can be morbidity mortality or incidence
quantifies increase or decrease in those relative to general population

58
Q

what is the p value

A

measure of statistical significance
probability of an event occurring due to chance alone
higher p value = higher probability the event can be explained by chance
from 0.0 to 1.0
cut offs 0.05/0.01

Epidemiology (23 decks)

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