tetano
Editor, Senior Moderator
Am J Epidemiol
. 2021 Apr 13;kwab107.
doi: 10.1093/aje/kwab107. Online ahead of print.
Consider This Before Using the SARS-CoV-2 Pandemic as an Instrumental Variable in an Epidemiological Study
Michelle C Dimitris[SUP] 1 2 [/SUP], Robert W Platt[SUP] 1 [/SUP]
Affiliations
Abstract
Epidemiologists sometimes use external sources of variation to explore highly-confounded exposure-outcome relationships or exposures that cannot be randomized. These exogenous sources of variation, or natural experiments, are sometimes proposed as instrumental variables to examine the effects of a given exposure(s) on a given outcome(s). Previous epidemiological studies have applied this technique using famines, earthquakes, weather events, and previous pandemics as exogenous sources of variation for other exposures; interest in applying this technique using the current severe acute respiratory system coronavirus 2 (SARS-CoV-2) pandemic is already documented. Yet, large-scale events like these likely have broad and complicated impacts on human health, which almost certainly violates the exclusion restriction assumption of instrumental variable analyses. We review the assumptions of instrumental variable analyses, highlight previous applications of this method with respect to natural experiments with broad impacts or "shocks", and discuss how these relate to our current observations of the SARS-CoV-2 pandemic. While we encourage thorough investigation of the broad impacts of the SARS-CoV-2 pandemic on human health, we caution against its widespread use as an instrumental variable to study other exposures of interest.
Keywords: COVID-19; Causal methods; SARS-CoV-2; instrumental variable; natural experiment; pandemic; quasi-experiment.
. 2021 Apr 13;kwab107.
doi: 10.1093/aje/kwab107. Online ahead of print.
Consider This Before Using the SARS-CoV-2 Pandemic as an Instrumental Variable in an Epidemiological Study
Michelle C Dimitris[SUP] 1 2 [/SUP], Robert W Platt[SUP] 1 [/SUP]
Affiliations
- PMID: 33847743
- DOI: 10.1093/aje/kwab107
Abstract
Epidemiologists sometimes use external sources of variation to explore highly-confounded exposure-outcome relationships or exposures that cannot be randomized. These exogenous sources of variation, or natural experiments, are sometimes proposed as instrumental variables to examine the effects of a given exposure(s) on a given outcome(s). Previous epidemiological studies have applied this technique using famines, earthquakes, weather events, and previous pandemics as exogenous sources of variation for other exposures; interest in applying this technique using the current severe acute respiratory system coronavirus 2 (SARS-CoV-2) pandemic is already documented. Yet, large-scale events like these likely have broad and complicated impacts on human health, which almost certainly violates the exclusion restriction assumption of instrumental variable analyses. We review the assumptions of instrumental variable analyses, highlight previous applications of this method with respect to natural experiments with broad impacts or "shocks", and discuss how these relate to our current observations of the SARS-CoV-2 pandemic. While we encourage thorough investigation of the broad impacts of the SARS-CoV-2 pandemic on human health, we caution against its widespread use as an instrumental variable to study other exposures of interest.
Keywords: COVID-19; Causal methods; SARS-CoV-2; instrumental variable; natural experiment; pandemic; quasi-experiment.