Background:Modern theories define chronic pain as a multidimensional experience the result of
complex interplay between physiological and psychological factors with significant impact on
patients’ physical, emotional and social functioning. The development of reliable assessment
tools capable of capturing the multidimensional impact of chronic pain has challenged the medical
community for decades. A number of validated tools are currently used in clinical practice
however they all rely on self-reporting and are therefore inherently subjective. In this study
we show that a comprehensive analysis of physical activity (PA) under real life conditions may
capture behavioral aspects that may reflect physical and emotional functioning.
Methodology:PA was monitored during five consecutive days in 60 chronic pain patients and 15
pain-free healthy subjects. To analyze the various aspects of pain-related activity behaviors
we defined the concept of PA ‘barcoding’. The main idea was to combine different features of PA
(type, intensity, duration) to define various PA states. The temporal sequence of different
states was visualized as a ‘barcode’ which indicated that significant information about daily
activity can be contained in the amount and variety of PA states, and in the temporal structure
of sequence. This information was quantified using complementary measures such as structural
complexity metrics (information and sample entropy, LempelZiv complexity), time spent in PA
states, and two composite scores, which integrate all measures. The reliability of these
measures to characterize chronic pain conditions was assessed by comparing groups of
subjects with clinically different pain intensity.
Conclusion:
The defined measures of PA showed good discriminative features. The results suggest that
significant information about pain-related functional limitations is captured by the
structural complexity of PA barcodes, which decreases when the intensity of pain increases.
We conclude that a comprehensive analysis of daily-life PA can provide an objective
appraisal of the intensity of pain.