Testing self-report time use diaries against objective instruments in real time

This study provides a new test of time use diary methodology, comparing diaries with wearable cameras and accelerometers. A volunteer sample of respondents (n = 148) completed conventional self-report paper time use diaries using the standard UK Harmonized European Time Use Study instrument, while wearing a camera recording images of their activities (approximately 1,500–2,000 images/day) and an accelerometer tracking their physical activity (PA). Of the initial 148 participants, 131 returned usable diary and camera records and 124 also provided a usable whole-day accelerometer record. The comparison of the diary data with the camera and accelerometer records supports the diary methodology at both the aggregate (sample) and individual levels. It provides evidence that time use data could be used to complement physical activity questionnaires, providing population-level estimates of PA. It also implies new opportunities for investigating techniques for calibrating metabolic-equivalent-of-task attributions to daily activities using large-scale, population-representative time use diaries.