Epidemiology

Question 1

what is epidemiology?

Answer 1

• the study of populations in order to determine the burden - frequency, distribution and trends of disease
• identifies risk factors for disease and helps determining optimal treatment approaches to clinical practice and disease prevention

Question 2

what are the major roles of epidemiology?

7

Answer 2

• monitor infectious and non-infectious diseases
• study natural history of diseases
• investigation of disease risk factors
• health care needs assessment
• development of preventative programmes
• evaluation of interventions
• health service planning

Question 3

what are the three types of epidemiological study?

Answer 3

• descriptive (observational)
• analytic (observational) - case control, cohort
• interventional/experimental

Question 4

what does descriptive epidemiology measure?

Answer 4

measures disease frequency
* prevalence
* incidence

Question 5

what is prevelance?

Answer 5

• measurement of all individuals affected by the disease within a particular period of time or point in time (Percentage)
• number of affected individuals / total number in population
• estimates from cross-sectional studies or registers
• estimates how common a condition is over a period of time / point in time

Question 6

what is incidence?

Answer 6

• measurement of the number of new individuals that contact a disease during a particular period in time (Rate)
• estimates from longitudinal studies or registers

Question 7

what is the difference between prevalence and incidence with diabetes and a common cold?

Answer 7

• diabetes has a low incidence and high prevalence as not many people are diagnosed in a year but it is long term so many have it at a given time
• a common cold has a high incidence and low prevalence as many people get a cold each year but not many have it at any given time

Question 8

what are the main variables of a descriptive study? what does it identify?

Answer 8

identifies changes in incidence or prevalence over time
* time
* place
* person

or when where who

Question 9

what are the andvantages of sampling?

4

Answer 9

• reduces number of individuals to be sampled
• reduces cost
• higher response rate
• higher quality of information collected

Question 10

what are the different sampling techniques?

5

Answer 10

• simple random sampling (table of random numbers)
• systematic sampling (selected at random intervals from list)
• stratfied sampling (ensures small sub-groups adequately represented)
• cluster sampling (use of groups as sampling units e.g. school classes)
• multi-stage sampling (combines above techniques)

Question 11

what are examples of bias and errors in surveying?

5

Answer 11

• sampling bias / selection bias
• response bias / information bias
• measurement error
• observation error observation variation
• loss to follow-up

Question 12

what is an index?

Answer 12

• needed to measure disease
• a way to standardise observational error

Question 13

what are the properties of an ideal index?

9

Answer 13

• clear, unambiguous, non subjective
• ideally correspond with clinically important stages of the disease
• indicate treatment need
• reproducible
• not time consuming
• acceptable to patient - not harmful
• amenable to statistical analysis
• allow comparison with other studies

Question 14

what index measures dental health/disease?

Answer 14

DMFT/dmft index for caries
* DMFT - decayed, missing, filled teeth in permanent teeth
* dmft - decayed, missing, filled teeth in primary teeth

dmf/def index fro deciduous teeth
* e = extraction/exfoliated teeth at age 6+ but only score c,d,e teeth
* if mixed dentition, only record permanent teeth

Question 15

what are the limitations of the DMF index?

6

Answer 15

• teeth extracted for reasons other than caries
• influenced by abcess
• difficulty in differentiating fissure-sealant from restorations - underestimate caries
• influenced by past disease activity
• treshold criteria of disease may vary
• cannot be used for root caries

Question 16

what are the stages of dental caries?

Answer 16

• sub-clinical decay
• decay in enamel (visible) d1mft
• decay in dentine (visible) d3mft
• pulpal decay

Question 17

how are epidemiology surverys calibrated?

Answer 17

• number of participants selected for calibration
• potential dental epidemiology examiners examine and chart each participant
• compare results - assess inter-observer variation
• outlier dental examiners not able to participate in epidemiological programme

Question 18

describe the index for fluorosis (TFI)

Answer 18

• TF0-TF4
• TF0 - no fluorosis
• TF1,2 - slight mottling
• TF3,4 - distinct white patches
• fluorosis needs to be seen across the midline

Question 19

describe the index of orthodontic treatment need (IOTN)

Answer 19

• assessed need and eligibility of children for NHS orthodontic treatment
• dental health component (DHC) has 5 grades - grade 1 almost perfect, **grade 5 severe dental health problems **
• aesthetic component (AC) scale of 10 colour photographs showing different levels of dental attractiveness - used for borderline cases with grade 3 DHC

Question 20

what indices are used with periodontal disease?

3

Answer 20

• plaque indicies
• gingivitis indices
• periodontitis indices - BPE