Table 1 Description and examples of mechanisms through which external factors can impact SWD studies
Scenario | Description | Example |
|---|---|---|
Confounding by calendar time | External factors that vary over time and affect the outcome independently of the intervention under study | Statewide policies limiting initial opioid prescriptions to a 7 day-supply |
Early intervention adoption (noncompliance) | Partial or full adoption of the intervention before its scheduled roll-out time; such events differentially impact intervention and control clusters | Use of opioid overdose reversal medication, naloxone, by first responders prior to the scheduled roll-out time for the community |
Time-varying effect modification | External factors that differentially impact the outcome overtime; depending on whether or not they are receiving the intervention | Changes in insurance policies to limit access to standard opioid treatments |