Measuring Health and Disease

Question 1

Define prevalence.

What is it useful for?

Answer 1

• The proportion of people in a
  population of known size who have a
  particular disease at a specified point in
  time, or over a specified period of time.
• Useful for planning services.

= All cases / Population at risk.

Question 2

Define incidence.

Answer 2

• The number of new cases over
  a period of time in a population of known
  size.

= Number of new cases / Population at risk.

Question 3

List 5 reasons for measuring health.

Answer 3

1 - To find prevalence / incidence.

2 - To identify longitudinal trends in disease.

3 - To identify differences in disease patterns between different populations or locations.

4 - To improve service planning (prevalence!).

5 - To measure the effectiveness of interventions.

Question 4

List 7 sources of information for health status.

Answer 4

1 - Census.

2 - Death certifications.

3 - Health Survey for England (HSE).

4 - General Lifestyle Survey.

5 - Hospital Episode Statistics (for health service usage).

6 - General practice research databses, e.g. CPRD, THIN.

7 - Regional audits / surveys.

Question 5

List 7 key statistics that are commonly used in measuring health and disease.

Answer 5

1 - Birth rates.

2 - Total fertility rates.

3 - General fertility rate

4 - Incidence.

5 - Prevalence.

6 - Crude mortality rates.

7 - Standardised mortality rates.

Question 6

Define birth rate.

Answer 6

The number of live births per 1000 population.

Question 7

Define general fertility rate.

Answer 7

The number of live births per 1000 women aged 15-44.

Question 8

Define total fertility rate.

Answer 8

The average number of children that a woman would bear if they experienced the age-specific fertility rates at that point in time.

Question 9

List 3 reasons for measuring infant mortality.

Answer 9

1 - Highly correlated with expectation of life.

2 - Highly correlated with overall economic status.

3 - High infant mortality rates are amenable to change through public health measures:

• Care of pregnant women.
• Infant immunisation.
• Nutrition programmes.

Question 10

Define crude mortality rate.

Answer 10

• Crude mortality rate = total number of deaths in 1 year / total mid-year population.

Question 11

Define mid-year population.

Answer 11

The mean of the population on 1 January and the population on 31 December of a year.

Question 12

List 3 disadvantages of using mortality data as a measure of population health.

Answer 12

1 - Potential for error.

2 - Death may result from many diseases acting in conjunction.

3 - Some diseases have high mortality rate and death occurs quickly, whereas others are long-term and resource intensive but rarely cause death.

Question 13

List 4 advantages of using mortality data as a measure of population health.

Answer 13

1 - It is a legal requirement in the UK to register each death.

2 - There is little delay in collection of data.

3 - International classification of diseases ensures comparability.

4 - Cheap source of health data.

Question 14

What is direct standardisation?

Answer 14

• Where age-specific rates from a study population are applied to a standard population.
• Used to answer the question “what would
  be the death rate in the standard
  population if it had the age-specific death rates experienced by the population I
  am looking at?”.

Question 15

List 2 advantages of using direct standardisation.

Answer 15

1 - Can be used to compare disease rates across areas and time.

2 - Can be used to assess the relative burden of different diseases in one population.

Question 16

List 2 disadvantages of using direct standardisation.

Answer 16

1 - Requires age-specific rates, which are not always available at a local level.

2 - Rates may not be stable for a small number of events.

Question 17

What is indirect standardisation?

Answer 17

• Where age-specific rates from a standard population are applied to a study population.
• Used to answer the question “what would
  be the death rate in the population i am looking at if it had the age-specific death rates experienced by the standard population?”.

Question 18

List 2 disadvantages of using indirect standardisation.

Answer 18

1 - Areas cannot be directly compared.

2 - Does not give an idea of the actual burden of disease.

Question 19

List 5 possible explanations for the association between socioeconomic deprivation and health.

Answer 19

1 - Artefacts of measurement error (minor).

2 - Social selection (minor).

3 - Behavioural / cultural (major).

4 - Psychosocial (major).

5 - Material / structural conditions (major).

Question 20

Define artefact.

Answer 20

Where observed associations are not genuine, but exist because of the ways in which we measure health and deprivation.

Question 21

Define social selection.

Answer 21

Where health determines socio-economic status (rather than where socio-economic status determines health).

Question 22

List 3 behavioural / cultural factors that are a disadvantage to health.

Answer 22

People in deprived areas are more likely to:

1 - Smoke.

2 - Eat poor diets.

3 - Not exercise.

Question 23

Describe the general psychosocial theory for the association between health and socioeconomic deprivation.

Answer 23

The stress of working in poorly paid, low status jobs with little autonomy creates biological changes in the body, which in turn creates patho-physical changes.

Question 24

Define social capital.

Answer 24

The amount to which people are connected within their community through relationships and have a shared sense of identity.

Question 25

Give an example of an advantage of indirect standardisation.

Answer 25

Doesn’t require age specific rates for the study population (as rates from the standard population are being applied to the study population, then absolute values of observed vs expected are compared).

Question 26

What is a standardised mortality ratio (SMR)?

Answer 26

Standardised mortality ratio = observed number of deaths in study population / expected number of deaths in study population.