And in fact: > Habitual coffee intake was self-reported as cups per day, as part of the touchscreen questionnaire at baseline with the question ‘How many cups

And in fact: > Habitual coffee intake was self-reported as cups per day, as part of the touchscreen questionnaire at baseline with the question ‘How many cups of coffee do you drink a day?’ (38). So, yes, it's self-reported in a non-standardized unit.