This paper has recently gained traction in the media and I am attempting to re-calculate the p values reported in the regression analysis in Table 2 of this paper (https://jamanetwork.com/journals/jamasurgery/fullarticle/10.1001/jamasurg.2019.5423). However, I appear to be obtaining different results. I am assuming that the outcome variable is the number of hospitalizations (e.g for those less than 18 year olds, the values would be 74, 21, 117, 62, & 335) and that the predictor variable is the year (2014,2015, 2016, 2017, 2018). However, upon analysis in R, I am calculating a p value of 0.172 for the regression coefficient. This appears to be an issue for the other p values as well but perhaps I am simply setting up the regression incorrectly?
My question is, how were these p values calculated? The paper is a bit vague. I've been asking around several forums and haven't been able to receive an answer. Therefore, if someone can help me out, it would be much appreciated.