Table A5: Risk of Bias Among Observational Trials of VNS Comparing High Stimulation and Low Stimulation in Adults.
| Author, Year | Appropriate Eligibility Criteria | Appropriate Measurement of Exposure | Appropriate Measurement of Outcome | Adequate Control for Confounding | Complete Follow-Up |
| Helmers et al, 2011 (13) | No limitations | No limitations | No limitations | No limitationsa | No limitations |
| Bernstein et al, 2007 (14) | No limitations | No limitations | No limitations | Limitationsb | No limitations |
Abbreviations: VNS, vagus nerve stimulation.
a
This is a retrospective cohort study with the inherent limitations of retrospective studies. However, Helmers et al attempted to control for confounding by adjusting the results based on several characteristics including age, sex, use of drug therapy, and other health conditions (including mental health).
b
This study did not make adjustment for any confounding.