Lecture 13: Injury epidemiology - Methodological challenges and study design Flashcards
How is the burden of injury recorded in NZ?
- NZHIS (new zealand health information service, part of the ministry of health)
- ACC claims database
- collected for a different purpose (compensate workers healthcare costs and rehabilitation)
what are the pros and cons of the NZHIS?
pros:
- coding is internationally comparable
- subgroup by risk markers (ethnicity, gender, age group)
cons:
- exclude less serious injuries that still impact lives
what are the pros and cons of the ACC claims database?
pros:
- captures non-hospitalised injuries
cons:
- major bias towards earners
- treatment claims (96%) little contextual information
what is ACC
everyone in NZ is covered by ACC’s no-fault scheme if they’re injured by an accident.
helps stop people from sueing.
name a few more data sources for recording the burden of injury?
- agency databases
- national surveys
- injury research publications
- research projects
give examples of agency databases and what they record.
- Traffic is recorded by Crash Analysis System (CAS)
- drowning: water safety NZ
- fires: fire service commision
- suicide: ministry of health
give an example of a national survey
NZ Health Survey
give an example of an injury research publication
Injury research publications
give an example of a research projects
using coronial files to investigate fire fatalities
what are the things we need to consider about this data collection?
- the purpose for which the data was collected
- how data was collected
- what the denominator is
- potential biases - what data might be missed
what can be used as a denominator? what could be the limitations?
- Can use the NZ Census population
Limitations:
- undercount in 2018
- exposure is not constant - may be transient
- total population may not be the best denominator
what potential biases could arise when collecting data?
injuries that don’t result in healthcare provision
what are the type of epidemiological study designs?
- systematic reviews
- descriptive studies - cross-sectional
- cohort
- case-control
- randomised controlled trial
- ecological
what are the challenges of quantifying risk and protective factors?
- exposure to risk is not consistent
- risk factors may be transient or short term
- no or short lag time between exposure and outcome
- multiple contributing causes
- need to consider confounding by other causes
- outcomes are rare in the general public so need large sample sizes
- those affected are often young and mobile which leads to lower participation rates, difficult to follow-up
what can a descriptive study do?
describe factors associated with injury, but not whether they are causal
what are the pros of injury cohort studies?
- temporal relationship
- exposure to risk information
- can measure many different outcomes
- can use existing datasets with high-risk populations
what are the cons of injury cohort studies?
- rare outcomes (most of injury) need very large sample size
- expensive and long follow up
- loss to follow up/ attrition
- difficult to measure short term/transient exposures (exposure might change)
- confounding
what are the pros of injury case-control studies?
- many different exposures for single outcome
- good for rare events - efficient and needs a smaller sample
- good for short terms risk factors
- no loss to follow up
- controls representative of exposure
what are the cons of injury case-control studies?
- no incidence rates; relative risk is measured by odds ratio
- confounding
- response rates very important due to selection bias (similar to loss to follow up)
- recall bias: misclassification of exposure
- control selection is very important
how do controls need to be selected for a case control study?
need to be selected on the basis of transient exposure.
how are randomised controlled trials useful for injuries?
- they are good for testing interventions
- but we can’t randomize potentially harmful exposures or interventions (due to equipoise)
what are the types of randomised controlled trials?
- individual or group (cluster) randomisation
- community intervention trials
what is the difference between a community intervention trial and group randomisation
community intervention is when you design interventions to improve in one community
if you had 3 communities with the intervention, and three communities without it, this would be a ‘cluster’ or ‘group’ randomisation
what is an ecological study design?
- recognition that environmental (physical and social) determinants play an important part in the causes of injury
- looks at differences between groups rather than individuals, defined by place and time.
- exposure and outcome measures are at the level of the whole group
what are the pros of ecological studies?
pros:
- they are useful for injury prevention policy evaluation
- can use existing data
- low cost
- convenient
what are the cons of ecological studies?
- reliability of data
- no direct estimate of rate or injury in exposed, unexposed, unmeasured confounding
what is important to consider in terms of cause?
causes of causes!
- environmental or political cause
*see notes on haddon matrix*
how has the view of injury changed?
- injury is now considered to be a public health problem to be systematically studied and addressed
- research and evidence shows that most injuries and predictable and therefore preventable - they are not accidents!
- incidence of injury and prevention of injury is closely linked with policy decisions: social, mental health, alcohol. transport
