The Experience Sampling Method in Small Fiber Neuropathy: The Influence of Psychosocial Factors on Pain Intensity and Physical Activity

Purpose: Small fiber neuropathy (SFN) is characterized by neuropathic pain, associated with decreased quality of life (QOL). It remains unclear which psychosocial factors play a role in SFN. The experience sampling method (ESM) allows a profound understanding of the real-time fluctuations in reaction to events. The main goal of this study was to increase knowledge of the interrelationships between pain intensity, physical activity, and psychosocial factors in patients with SFN in daily practice over time. Patients and Methods: A prospective observational ESM study with the PsyMate (c) application (smart-eHealth GmbH, Luxembourg) was conducted at the Adelante location of Maastricht University Medical Center+ in the Netherlands. Participants with idiopathic SFN, older than 18 years, with an indication for rehabilitation, were included. Pain intensity, fatigue, positive and negative affect, physical activity, avoidance behavior, and pain catastrophic thoughts were incorporated into the ESM questions. Participants received 10 beep signals per day followed by the above-mentioned questions, for consecutive 7 days. The results were analyzed with linear mixed-effect models. Results: Twenty-one participants were included with a mean age of 48.24 (SD +/- 13.89) years, of whom 76.2% were female. More pain (now) resulted in more physical activity (later) (a) and more physical activity (now) resulted in more pain (later) (b). The first association (a) is influenced by pain catastrophic thoughts and fatigue, and the second (b) by an increase in affective states and a lower level of avoidance behavior. Conclusion: In idiopathic SFN, pain intensity, and physical activity showed a 2-sided association, influenced by catastrophic thoughts, fatigue, affective states, and avoidance behavior.