Thanks for your response, Bob! You're correct in that they don't define 'cup', the study used a questionnaire that left that answer up to the respondent - how many cups of coffee do you drink per day, etc. In the paper itself, they highlight that potential drawback: "Importantly for the current study, there also remains ambiguity in the individual interpretation of a cup serving of coffee, however, this is a broader issue as the standardisation of a unit of coffee is yet to be established in literature, particularly for observational studies (62)."

I didn't go into a huge amount of detail in this piece, mainly because I like to keep things short and report the results. But the paper is a decent read, and I'm happy to email you a copy of the full piece if you'd like to take a look.

Overall, more coffee correlated with higher risk of dementia and smaller brain volume, when ruling out other factors.

(PS-most studies don't write their abstract in a way that would be most informative for the general public. Abstracts have pretty tight limits, so all the vital information can't be packed in. Unfortunately paywalls are always an issue, but emailing the authors of a study will easily get you access to the paper if you so choose :) ).