Methodological considerations for the quantification of self-reported caffeine use.
BACKGROUND
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.


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.
Addicott
Merideth A
MA
Department of Radiology, Wake Forest University School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157, USA.
Yang
Lucie L
LL
Peiffer
Ann M
AM
Laurienti
Paul J
PJ
D000293:Adolescent; D000328:Adult; D002110:Caffeine / Q000008:administration & dosage* / Q000032:analysis; D003625:Data Collection / Q000379:methods*; D006184:Habits; D006801:Humans; D008875:Middle Aged; D012189:Retrospective Studies; D012463:Saliva / Q000737:chemistry; D012650:Self Disclosure; D011795:Surveys and Questionnaires; D055815:Young Adult
D002110:Caffeine