Educational differences in the validity of self-reported physical activity

The assessment of physical activity for surveillance or population based studies is usually done with self-report questionnaires. We studied if the validity of a much used self-reported physical activity questionnaire -the International Physical Activity Questionnaire (IPAQ) was different according to the level of education of the respondents.
In a paper just published in BMC public health, we compared physical activity as assessed with IPAQ to physical activity assessed with accelerometers (i.e. an objective measure of physical activity) and analysed if the results of these two measurements were better associated in higher than in lower educated people. This was indeed the case. The validity of IPAQ was moderate at best among higher educated respondents, but very poor among lower educated respondents. Our results suggest that questionnaires such as IPAQ should not be used among the lower educated.