Legend: a Inflation in US dollars was adjusted to 2021 value using the Consumer Price Index Inflation Calculator of the U.S. Bureau of Labor Statistics. b Per-physician payment was calculated among physicians receiving payments.
*p<0.001
Abbreviations: 95% confidence interval (95% CI), interquartile range (IQR), SD (standard deviation)
Supplemental Material 1. Detailed data analysis methodology
The extracted payment data was descriptively analyzed, including average, standard deviation, median, and interquartile range. Per-physician payments were calculated among physicians who received payments, as the majority of gastroenterologists did not receive research payments from the healthcare industry. The payments were analyzed by payment year and content of payments. For associated research payments, per-physician payments were calculated as total payments divided by the number of principal investigators in a research payment, and total research payments were calculated by the number of gastroenterologists times the payment per principal investigator because some research payments included principal investigators with other specialties.
Furthermore, the study assessed yearly trends in the number of gastroenterologists receiving payments and per-physician payments using population-averaged generalized estimating equations (GEE) at the individual physician level. The annual number of physicians receiving payments and per-physician payments were examined using log-linked GEE with Poisson distribution and negative binomial GEE, respectively. Additionally, the trend in the total amounts of annual research payments was assessed by a linear GEE model. Inflation in US dollars was adjusted to 2021-dollar values using a Consumer Price Index inflation calculator of the U.S. Bureau of Labor Statistics ( https://www.bls.gov/data/inflation_calculator.htm). Institutional board review and approval were not required for this study, as the study was designed as a non-human subjects study of publicly-available data.
Supplemental Material 2. Associated research payments to preclinical trials and registered clinical trials between 2014 and 2021.