Agreement of accelerometer and a physical activity questionnaire in adults with intellectual disabilities

Purpose
To assess the level of agreement between accelerometer and proxy-respondent questionnaire measurement of the physical activity levels of adults with intellectual disabilities.

Methods
In Glasgow, UK, from May to September 2009, the main carer of participants with intellectual disabilities was asked to complete the International Physical Activity Questionnaire—Short Version, detailing the participants' regular physical activity levels. Participants were also invited to wear an ActiGraph GT1M accelerometer for seven consecutive days, during all waking hours. The level of agreement from the two measurements was compared using the Bland–Altman method.

Results
There is limited agreement between physical activity and sedentary behavior measured with accelerometer and proxy-respondent questionnaire. The 95% limits of agreement for both moderate activity and sedentary activity were − 44.48 to 34.20 min per day and − 8.41 to 6.79 h per day, respectively. As physical activity increased above 10 min per day, the agreement between the accelerometer and International Physical Activity Questionnaire—Short Version data decreased further.

Conclusion
It remains uncertain whether questionnaire methods have sufficient reliability for use in surveillance of physical activity levels of adults with intellectual disabilities.