TY - JOUR T1 - Validation of short term recall of mobile phone use for the Interphone study JF - Occupational and Environmental Medicine JO - Occup Environ Med SP - 237 LP - 243 DO - 10.1136/oem.2004.019281 VL - 63 IS - 4 AU - M Vrijheid AU - E Cardis AU - B K Armstrong AU - A Auvinen AU - G Berg AU - K G Blaasaas AU - J Brown AU - M Carroll AU - A Chetrit AU - H C Christensen AU - I Deltour AU - M Feychting AU - G G Giles AU - S J Hepworth AU - M Hours AU - I Iavarone AU - C Johansen AU - L Klæboe AU - P Kurttio AU - S Lagorio AU - S Lönn AU - P A McKinney AU - L Montestrucq AU - R C Parslow AU - L Richardson AU - S Sadetzki AU - T Salminen AU - J Schüz AU - T Tynes AU - A Woodward Y1 - 2006/04/01 UR - http://oem.bmj.com/content/63/4/237.abstract N2 - Aim: To validate short term recall of mobile phone use within Interphone, an international collaborative case control study of tumours of the brain, acoustic nerve, and salivary glands related to mobile telephone use. Methods: Mobile phone use of 672 volunteers in 11 countries was recorded by operators or through the use of software modified phones, and compared to use recalled six months later using the Interphone study questionnaire. Agreement between recalled and actual phone use was analysed using both categorical and continuous measures of number and duration of phone calls. Results: Correlations between recalled and actual phone use were moderate to high (ranging from 0.5 to 0.8 across countries) and of the same order for number and duration of calls. The kappa statistic demonstrated fair to moderate agreement for both number and duration of calls (weighted kappa ranging from 0.20 to 0.60 across countries). On average, subjects underestimated the number of calls per month (geometric mean ratio of recalled to actual = 0.92, 95% CI 0.85 to 0.99), whereas duration of calls was overestimated (geometric mean ratio = 1.42, 95% CI 1.29 to 1.56). The ratio of recalled to actual use increased with level of use, showing underestimation in light users and overestimation in heavy users. There was substantial heterogeneity in this ratio between countries. Inter-individual variation was also large, and increased with level of use. Conclusions: Volunteer subjects recalled their recent phone use with moderate systematic error and substantial random error. This large random error can be expected to reduce the power of the Interphone study to detect an increase in risk of brain, acoustic nerve, and parotid gland tumours with increasing mobile phone use, if one exists. ER -