Source
Department of Radiology, Wake Forest University School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157, USA.
Abstract
RATIONALE:
The field of research regarding the effects of habitual caffeine use is immense and frequently utilizes self-report measures of caffeine use. However, various self-report measures have different methodologies, and the accuracy of these different methods has not been compared.
MATERIALS AND METHODS:
Self-reported caffeine use was estimated from two methods (a retrospective interview of weekly caffeine use and a 7-day prospective diary; n = 79). These estimates were then tested against salivary caffeine concentrations in a subset of participants (n = 55).
RESULTS:
The estimates of caffeine use (mg/day) from the interview- and diary-based methods correlated with one another (r = 0.77) and with salivary caffeine concentrations (r = 0.61 and 0.68, respectively). However, almost half of the subjects who reported more than 600 mg/day in the interview reported significantly less caffeine use in the diary.
CONCLUSIONS:
Self-report measures of caffeine use are a valid method of predicting actual caffeine levels. Estimates of high caffeine use levels may need to be corroborated by more than one method.