title: Validation of different instruments for caffeine measurement among premenopausal women in the BioCycle study.
abstract: Effects of caffeine on women's health are inconclusive, in part because of inadequate exposure assessment. In this study we determined 1) validity of a food frequency questionnaire compared with multiple 24-hour dietary recalls (24HDRs) for measuring monthly caffeine and caffeinated beverage intakes; and 2) validity of the 24HDR compared with the prior day's diary record for measuring daily caffeinated coffee intake. BioCycle Study (2005-2007) participants, women (n = 259) aged 18-44 years from western New York State, were followed for 2 menstrual cycles. Participants completed a food frequency questionnaire at the end of each cycle, four 24HDRs per cycle, and daily diaries. Caffeine intakes reported for the food frequency questionnaires were greater than those reported for the 24HDRs (mean = 114.1 vs. 92.6mg/day, P = 0.01) but showed high correlation (r = 0.73, P < 0.001) and moderate agreement (К = 0.51, 95% confidence interval: 0.43, 0.57). Women reported less caffeinated coffee intake in their 24HDRs compared with their corresponding diary days (mean = 0.51 vs. 0.80 cups/day, P < 0.001) (1 cup = 237 mL). Although caffeine and coffee exposures were highly correlated, absolute intakes differed significantly between measurement tools. These results highlight the importance of considering potential misclassification of caffeine exposure.
authors: Epidemiology Branch, Division of Epidemiology, Statistics, and Prevention Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Rockville, MD 20852, USA.
authors: Karen C
authors: KC
authors: Schliep
authors: Enrique F
authors: EF
authors: Schisterman
authors: Sunni L
authors: SL
authors: Mumford
authors: Neil J
authors: NJ
authors: Perkins
authors: Aijun
authors: A
authors: Ye
authors: Anna Z
authors: AZ
authors: Pollack
authors: Cuilin
authors: C
authors: Zhang
authors: Christina A
authors: CA
authors: Porucznik
authors: James A
authors: JA
authors: VanDerslice
authors: Joseph B
authors: JB
authors: Stanford
authors: Jean
authors: J
authors: Wactawski-Wende
mesh_terms: D000293:Adolescent; D000328:Adult; D001628:Beverages; D002110:Caffeine / Q000008:administration & dosage*; D003069:Coffee; D004032:Diet / Q000706:statistics & numerical data; D015930:Diet Records; D005260:Female; D006801:Humans; D011939:Mental Recall; D017697:Premenopause; D054928:Validation Studies as Topic; D016387:Women's Health; D055815:Young Adult
chemical_list: D003069:Coffee; D002110:Caffeine