Methodological considerations for the quantification of self-reported caffeine use

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.

Use of caffeinated substances and risk of crashes in long distance drivers of commercial vehicles: case-control study

“…Drivers were asked to describe consumption patterns over that month, in quantity and frequency. Amounts consumed were described in an open ended format and then coded based on guidelines developed by Addicott and colleagues, 25 such that a "cup of coffee" or a "can of energy drink" contained 100 mg of caffeine and a cup of tea or can of caffeinated soft drink contained 50 mg of caffeine. Caffeine tablets purchased over the counter contain 100 mg per tablet and were therefore coded as such.…”

“…Low caffeine users consumed less than 200 mg a day, moderate caffeine users 200-400 mg a day, and high caffeine users more than 400 mg a day. 25 substances such as "speed" (amphetamine), cocaine, and ecstasy (3,4 methylenedioxymethamphetamine). If drivers said they had used any of these substances they were then asked further detail about the frequency and amount over the same period.…”

“…Despite the considerable variability in the self reported quantities of caffeinated beverages consumed as well as in consumption patterns, previous research has reported a reasonable degree of accuracy between self report and objective testing, albeit limited at the higher consumption levels. 25 Taking this into account, we minimised the potential for reporting bias associated with the quantification of caffeine by only descriptively presenting the dose measures and not including them in the parsimonious model.…”

“…Recently renewed fatigue management guidelines for all commercial drivers 25 imposed limits on the length of continuous driving periods, the objective being to "provide sufficient rest breaks" in a full day of driving. These guidelines also caution against the use of illegal stimulants to manage fatigue, though the consumption of caffeinated beverages is suggested as useful for improving alertness for a short time.…”

Caffeine, Cognition, and Socioeconomic Status

“…Multiple regression analyses reported here entered caffeine intake on an interval scale and retained the main findings of the preceding categorical analyses. Studies of the validity of self-reported caffeine intake suggest that in the normal range of caffeine intake (< 1200 mg/daily), these questionnaire methods are valid, but when higher intakes are reported, other supportive measures are required to corroborate this estimation [29].…”