I was reading the following study on associations between bilirubin and CAD (coronary artery disease). They looked at the bilirubin association, and the genes that cause Gilbert's syndrome, which increases bilirubin concentrations. Study here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2648823/
The study states in the abstract:
"Both polymorphisms showed a strong association with bilirubin levels with higher levels for homozygote carriers of the minor allele."
But then goes on to say, a few sentences later:
"Logistic regression analysis revealed low bilirubin levels but not the UGT1A1 polymorphisms to be significantly associated with CAD: OR (95%CI) 0.90 (0.86–0.94), p=2.6×10−6 for men and 0.77 (0.68–0.87), p=3.2×10−5 for women, respectively for each 0.1 mg/dl increase of bilirubin."
How can we see a "strong association" between the gene that causes gilberts sydrome and bilirubin levels but not see an associatoin between the gene and CAD risk? If the study is stating bilirubin is significantly associated with CAD risk, and the polymorphism is strongly associated with the level of bilirubin, shouldn't it follow that we would see an association between the polymorphism and CAD?
My guess is that polymorphism correlation to bilirubin levels isnt actually all that strong, or that the association between bilirubin and CAD isnt all that strong, or both. Hoping someone could offer some thoughts on what they think is going on.