Introduction to Epidemiology Flashcards
What is epidemiology
the study of populations in order to determine the frequency and distribution of disease
what does epidemiology help to identify
risk factors for disease and determining optimal treatment approaches to clinical practice and preventative medicine
what are the major roles of epidemiology
monitor infectious and non-infectious diseases
study natural history
investigations of disease risk factors
health care needs assessment
developing of preventative programs
evaluation of interventions and their effectiveness
health service planning
how is epidemiology used to monitor infectious diseases
monitor flue outbreaks which helps in planning for provision of flu
what is the natural history of disease
the course a disease takes in individual people from its pathological onset until its eventual resolution or death
what do we look at when studying natural history of diseases
are they: self limiting chronic fatal unknown
what does investigations of disease factors consist of
o Looking at the causes/determinants of diseases
what does epidemiology help in health care needs assessments
o What care services are required by particular population groups
how does epidemiology help in development of preventative programs
o Based on knowing risk factors of diseases and attempting to prevent exposure to these factors
what are the 3 main types of epidemiology studies
descriptive
analytic (observational)
intervention/experimental
what is descriptive epidemiology
measures of disease frequency and it is either prevalence or incidence
what is prevalence
o Measurement of all individuals affected by the disease within a particular period of time or point in time – a cross sectional point in the population
how is prevalence calculated
o Number of affected individuals (cases) divided by the total number of persons in population and is expressed as a percentage or fraction
what is prevalence obtained from
cross sectional studies or derived from registers
what is prevalence used as
an estimate of how common a condition is within a population over a certain period of time or point in time
what is incidence
a measurement of the number of new individuals who contract a disease during a particular period of time
how is incidence calculated
o Number of new cases or events during a specific period of time in a defined population
how is incidence estimates obtained
obtained from longitudinal studies or derived from registers
how is incidence expressed
o Expressed as a fraction
do we use incidence or prevalence for chronic incurable diseases
they have low incidence but high prevalence
we usually use prevalence - allows us to help in management
do we use incidence or prevalence for short duration curable conditions
they have high incidence but low prevalence because many people get a cold each year but few people actually have a cold at any given time so prevalence is low
what are the main variables for descriptive studies
Time, place, person OR when, where, who
what are the aims of time, place, person
- Identify changes in incidence or prevalence over time OR
- Determine incidence or prevalence of disease in different geographical areas OR
- Determine incidence/prevalence of disease in groups of individuals with different characteristics
what are the advantages of sampling
- Reduces number of individuals to be sampled
- Reduces cost
- Higher response rate
- Higher quality of information collected
what must samples be
The sample must be representative of population being investigated. The aim is to avoid bias.
what are the sampling techniques
simple random sample systemic sample stratified sample cluster samples multistage sampling
what are simple random samples
o Use of a table of random numbers
what is a systemic sample
o Individuals selected at regular intervals from population list
what is a stratified sample
o Ensures small sub-groups adequately represented
what is a cluster sample
o Use of groups as sampling units e.g school classes
what is multi-stage sampling
o Combines above techniques
what are the error
- Sampling bias/selection bias
- Response bias/information bias
- Measurement error
- Observer variation (intra- or inter-)
- Loss to follow up
what is response bias
o If you are not monitoring who is responding it could only be a certain group responding so you miss out groups in the population
what is observer variation
o When examining it has to be the same
how do we avoid measurement error when measuring disease
we use an appropriate index
what are the properties of an ideal index
- Clear, unambiguous, not subjective
- Ideally correspond with clinically important stages of the disease
- Indicate tx need
- Within the ability of examiners
- Reproducible
- Not time consuming
- Acceptable to patient
- Amenable to statistical analysis
- Allow comparison with other studies
what are dental indices
DMF index
dmf/def index
what are the limitations of the DMF index
- teeth extracted for reasons other than caries
- influenced by access e.g interproximal surface so could underestimate
- difficulty in differentiating fissure sealant from restorations – underestimate caries
- influenced by past disease activity
- threshold criteria of disease can vary – must specify
- cannot be used for root caries
what is the study used for epidemiology of dental caries in children
Descriptive cross-sectional epidemiology
NDIP in scotland
what does NDIP use
It uses cross sectional, descriptive dental surveys of school children
It has larger samples than UK decennial surveys
It involves standard examination criteria and trained and calibrated examiners
what is the aim of NDIP
It aims to inform:
- Parents of their child’s dental health status (basic NDIP)
- Advise Scottish government, NHS boards and other organizations of the oral disease prevalence in children in their area
what are the target groups for NDIP
p1 and 7
what happens in NDIP
- There is basic inspection for all children in p1 and p7 every year
- There is detailed inspection (epidemiology) for a sample of children every year
o Alternates each year between P1 and P7 - NHS board can add additional year groups
what is the basic inspection in NDIP
- Offered to every child in p1 and p7 classes of local authority schools
- Proportion of school rolls inspected = 85-90%
- Generates letter to parent
o Overall state of dental health of child
o Coveys degree of urgency with which appointment for attendance at dentist suggested for child - Not a detailed examination of each surface of each tooth
what does the detailed inspection consist of in NDIP
- More rigorous and comprehensive assessment
- Calibration of examiners
- Records status of each tooth surface in accordance with international epidemiology conventions (i.e d3mft: caries into dentine)
- Uses same clinical inspection criteria as SHBDEP
o Can there look at trends from 1987 re P1 children
what are the specific goals of the NDIP
- To inspect a representative sample of the p1 or p7 LA school population in any year
- To determine current levels of established tooth decay
- To illustrate the impact of deprivation on the dental health of 5&11 year old children in Scotland
how are the NDIP epidemiology surveys calibrated
- Number of children e.g 10 selected for calibration exercise
o High proportion should have caries - Potential dental epidemiology examiners then all examine and chart each child
- Compare results and assess inter-observer variation
- Outlier dental examiners not able to participate in epidemiological programme
what are the indices of fluorides
- Fluorosis index
- TF index
- Tooth surface index of fluorosis
- SCOTS index
what does the index of ortho tx need do
Assesses need and eligibility of children for NHS ortho treatment
Selects those that will benefit most
what are the 2 components of the index of orthodontic treatment need
dental health component
aesthetic component
what is the dental health component
o Goes from grade 1 which is almost perfection to grade 5 which is severe dental health problems
what is the aesthetic component
o Scale of 10 colour photographs showing different levels of dental attractiveness
o AC used for border-line cases with grade 3 DHC. If high AC score, NHS treatment is permissible
what are the indices for periodontal disease
plaque indices
gingivitis index
periodontitis indices
what are the plaque indices
o Debris index
o Plaque index
what are the gingivitis indices
o Modified gingival index
o Lobene index
what are the periodontitis indices
o Basic periodontal examiniation
