As multiple factors can elevate GGT levels,77 we used binomial tests to verify that the 180 duplication carriers were not enriched for GGT-altering drug usage (p = 0.55), high alcohol consumption (p = 0.85), heart failure (p = 0.23), or cancer (p = 1) and other diseases (p = 0.64) of the liver, gallbladder, and bile ducts, as compared to control individuals. Here, GGT1 is linked to heart failure.