Ecological Study Design

Question 1

What is an ecological study?

Answer 1

Observational study where data are analysed at the population or group level, rather than individual level

Question 2

What are ecological studies used for?

Answer 2

Often used to measure prevalence and incidence of disease – particularly when disease rare

Question 3

What are the advantages of ecological studies?

Answer 3

• Inexpensive
• Easy to undertake – use routinely collected data

Question 4

What are the disadvantages of ecological studies?

Answer 4

• Prone to bias & confounding
• Careful to extrapolating to individuals within the measurement areas or to higher population level

Question 5

Why do an ecological study?

Answer 5

Public health

Large scale comparisons

If individual measurements are not available

Disease rare

Question 6

What kinds of measurements are there in ecological studies?

Answer 6

Health outcomes

Ecological or exposure data

Question 7

What kind of ecological risk or exposure data exist?

Answer 7

Aggregate measure

Environmental measures

Global measures

Question 8

What are aggregated measures?

Answer 8

Data are summaries of individual level data.

Question 9

What are environmental measures?

Answer 9

Equivalent individual level data conceivable.

Question 10

What are global measures?

Answer 10

No equivalent individual level data.

Question 11

What types of ecological studies?

Answer 11

Geographical

Longitudinal

Migration

Question 12

What are geographical ecological studies?

Answer 12

Compare one geography with another.

Assesses one geography with another.

Question 13

What are longitudinal ecological studies?

Answer 13

• Population monitored to assess changes in disease over time
• Confounding factors may be included in the analysis

Question 14

What is migration ecological studies?

Answer 14

Migrant population data collected & analysed

Question 15

What is ecological fallacy?

Answer 15

Type of confounding specific to ecological studies

When relationships found for groups are believed to be true for individuals.

Question 16

How is confounding avoided during ecological data?

Answer 16

Regression modelling

Question 17

What kind of regression modelling is used in ecological studies?

Answer 17

• Poisson regression
• Negative binomial regression
• Multilevel modelling

Question 18

What is area-level exposure?

Answer 18

Some environmental exposures determined by area.

Question 19

What is exposure misclassification?

Answer 19

Proxy measures based on modelling may not adequately capture exposure of individual

Question 20

What is the ideal analysis for ecological studies?

Answer 20

Based on individual-level data.

Question 21

Why does exposure misclassification occur?

Answer 21

Exposures are modelled

Question 22

What is regression dilution bias?

Answer 22

Bias of effect size estimates towards the null

Question 23

What is ecological regression?

Answer 23

Where group is the unit rather than individual

Question 24

What are the implications of small excess relative risk on public health?

Answer 24

Even small excess relative risks applied to large numbers of people could result in large excess numbers of disease

Question 25

What was the aim of the BCM Cancer 2012 ecological study?

Answer 25

Test predictions of spatial variation that might arise as a result of environmental mechanisms & area-level socio-economic deprivation

Question 26

What is an aetiological hypothesis?

Answer 26

A primary factor influencing geographical heterogeneity of incidence is modulated by differences in environmental exposures

Question 27

What was the case data for the ecological study of BCM cancer 2012?

Answer 27

Patients diagnosed with primary osteosarcoma or Ewing sarcoma in GB between 1980-2005, less than 50 years old.

Question 28

How was population data obtained in the BMC cancer study 2012?

Answer 28

At small-area level, census ward in E&W and postcode sector

Question 29

How was the demographic data collected in the BMC cancer study?

Answer 29

Small-area demographic characteristics derived from the censuses

Question 30

Which statistical test was used for the BMC cancer 2012 study?

Answer 30

Negative binomial regression

Question 31

What were the findings for the MBC cancer study of 2012?

Answer 31

Females have a lower incidence of osteosarcoma if in higher levels of deprivation. Lower incidence of Ewing sarcoma associated with residence in densely populated areas and people without cars.

Question 32

What can be interpreted about osteosarcoma from the BMC cancer 2012 study?

Answer 32

For females, geographical heterogeneity of incidence is affected by the environment (deprived areas)

Question 33

What can be interpreted about Ewing sarcoma from the BMC Cancer 2012 study?

Answer 33

Geographical heterogeneity of incidence is affected by dense population and deprived.

Question 34

What is a Methodological Caveat?

Answer 34

A warning or proviso of specific stipulations, conditions, or limitations

Question 35

What was the aim of the type 1 diabetes Yorkshire ecological study?

Answer 35

Finding the Relationship between incidence of childhood type 1 diabetes & levels of nitrate in drinking water investigated.

Question 36

What was the study area of the type 1 diabetes Yorkshire ecological study?

Answer 36

Yorkshire Regional Health Authority

Question 37

What was the hypothesis of the type 1 diabetes Yorkshire ecological study?

Answer 37

Geographical heterogeneity of incidence of type 1 diabetes is modulated by differences in nitrate in drinking water

Question 38

What was the findings of the type 1 diabetes Yorkshire ecological study?

Answer 38

Diabetes incidence was positively associated with raised mean nitrate levels. Significant negative trends were found between standardised incidence ratios. Nitrate in drinking water may be a precursor of chemicals which are toxic to the pancreas