That there were no major differences in risk reduction between regular and decaf coffee suggests there's something in it, aside from its caffeine content, that could be contributing to these observed benefits. It also demonstrates that caffeine was in no way mitigating coffee's therapeutic effects. Of course, what we choose to add to coffee can just as easily negate the benefits -- various sugar-sweetened beverages were all significantly associated with an increased risk of diabetes. A learned taste for cream and sugar (made all the more enticing when they're designed to smell like seasonal celebrations) is likely one of the reasons why we associate coffee more with decadence than prudence.