Patients with chronic pain may have difficulties estimating their own physical 
activity level in daily life. Pain-related factors such as depression and pain 
intensity may affect a patients' ability to estimate their own daily life 
activity level. This study evaluates whether patients with Chronic Low Back Pain 
(CLBP) who are more depressed and/or report more pain indeed have a lower 
objectively assessed daily life activity level or whether they only perceive 
their activity level as lower. Patients with CLBP were included in a 
cross-sectional study. During 14days physical activity in daily life was 
measured, with both an electronic diary and an accelerometer. Multilevel 
analyses were performed to evaluate whether a higher level of depression and/or 
pain intensity was associated with a lower objectively assessed activity level 
or the discrepancy between the self-reported and objectively assessed daily life 
activity levels. Results, based on 66 patients with CLBP (mean RDQ score 11.8), 
showed that the objectively assessed daily life activity level is not associated 
with depression or pain intensity. There was a moderate association between the 
self-reported and objectively assessed activity levels (beta=0.39, p<0.01). The 
discrepancy between the two was significantly and negatively related to 
depression (beta=-0.19, p=0.01), indicating that patients who had higher levels 
of depression judged their own activity level to be relatively low compared to 
their objectively assessed activity level. Pain intensity was not associated 
with the perception of a patient's activity level (beta=0.12, ns).