I was looking at a paper by Pell JS 2009, regarding smoking and survival following acute coronary syndrome. Part of the analysis carried out in the paper was a logistic regression with results as shown below:
I have 3 questions about these results:
As seen in the univariate analysis, is it right to say that only serum cotinine (>0.9) is statistically significant, despite the p-value for serum cotinine being 0.005?
Has the strength of association between serum cotinine and all-cause death after adjustment has increased or decreased after multivariate analysis?
Given that the p-value has decreased but the point estimate and SE of all categories of serum cotinine has increased (except <=0.1 which has decreased) after multivariate analysis, I am more inclined to say it has increased but I am not sure.
Given the fact that of the 3 factors tested in multivariate analysis only age is associated with all-cause death, I was wondering if we could determine the nature of the association between serum cotinine and age given the changes of ORs for serum cotinine?
I understand that if serum cotinine and age are collinear, the p-value for serum cotinine would become less significant. Therefore, since this did not happen, are Age and serum cotinine independent from one another?
- Pell JS, Haw S, Cobbe S, Newby DE, et al. Secondhand smoke exposure and survival following acute coronary syndrome: prospective cohort study of 1261 consecutive admissions among never-smokers. Heart 2009;95:1415-1418