Two new studies came out recently on the benefits of coffee. The usual caveats apply, of course (see this pretty good CNN summary), but a few things make these two articles particularly strong as observational evidence:
- The European study looked at liver function in a subset and found evidence for better function in coffee-drinkers, lending some biological plausibility.
- The Multiethnic study found a stronger beneficial effect among younger participants - this is consistent with survivor bias diluting the effect in populations with a range of participants.
- The European study did a formal bias analysis which suggested that unmeasured confounding would have to be on the order of another smoking-level determinant to explain away the observed association.
- The simple fact that between the two of them, they span multiple countries and multiple races and ethnicities, with little evidence of heterogeneity.