Gotta wonder if that differential between caffeinated and decaf is about the caffeine or if the decaffeination process also removes other possibly beneficial compounds (including the known-beneficial diterpenoids).

Also, the 'cohort characteristics' are worth a look. What pops out to me is that 'ground' drinkers had a lower proportion of people with BMI >29 and T2DM, and higher one of never-smokers.