Raw Data for Unpublished Study "Healthy Women Show More Experimentally-Induced Central Sensitization Compared to Men"

Version sex_v01_20230409

Main authors: Alexandros Guekos, Janis Saxer, Diego Salinas Gallegos, and Petra Schweinhardt

The present data was collected from April 2021 to December 2022 for a study on sex-specific differences in central sensitization (CS) proxies in healthy young adults.

The results are to be published soon. A link to the manuscript will be provided.

Full details of the paradigm, the experimental setup, and the analysis will be given there. Therefore, the following description only summarizes the most important steps.

In brief, 66 subjects (33 men and 33 women) participated in a single experimental session during which a CS induction protocol consisting of repetitive noxious heat stimuli over about 12 minutes of 10 blocks at 48 degrees centigrade was applied to the lateral dorsum of the foot proximal to the malleolus. A sham protocol (where temperature remained at baseline for the whole time) was performed on the contralateral foot. Order of protocol and choice of starting side was pseudorandomly varied across participants. Participants had to rate mean temperature intensity per block on a scale from 0 (no sensation) to 200 (maximum tolerable pain) with 100 corresponding to the individual heat pain threshold (HPT).

The CS induction protocol has previously been published (Jürgens, Tim P., et al. "An improved model of heat-induced hyperalgesia?repetitive phasic heat pain causing primary hyperalgesia to heat and secondary hyperalgesia to pinprick and light touch." PLoS One 9.6 (2014): e99507, https://doi.org/10.1371/journal.pone.0099507) and validated (Scheuren, Paulina S., et al. "Pain?autonomic interaction: A surrogate marker of central sensitization." European journal of pain 24.10 (2020): 2015-2026, https://doi.org/10.1002/ejp.1645). Details on this CS induction protocol can be found in the two aforementioned publications.

In the present paradigm, two measures of CS proxies were collected before and about 20 minutes after CS induction.

On the one hand, mechanical sensitivity testing (by von 256 mN Frey filament and by soft brush of about 300 mN) was performed on the foot dorsum along five radial lines of 5 cm length (separated at 45 degrees) in the skin area adjacent to the primary area of painful stimulation. For the von Frey filament, testing was done every 5 mm along each line, always starting from the outermost point moving inwards (10 points in total). For the soft brush, strokes of 10mm were applied (5 strokes in total). Participants had to report a definite change in sensation w.r.t. to the outermost point.

On the other hand, the nociceptive withdrawal (NWR) reflex was elicited at the retromalleolar pathway of the sural nerve and surface electromyography (sEMG) was recorded from the biceps femoris (BF), rectus femoris (RF), and tibialis anterior (TA) muscles.

For NWR elicitation, the reflex threshold was first determined at the BF. For threshold determination, a single ascending staircase with either single electrical stimulations or triplets (at 2Hz) were used. From the triplets, only the muscle response to the third stimulation was analysed. The higher of the two obtained currents was then used as the NWR threshold.

Then 15 stimulations at 120% threshold current and 15 at 140% were applied. The order of stimulations was random with the restriction that not more than five identical stimulations in a row were allowed. The interstimulus interval was randomly varied between 5 and 15 s.

Every electrical stimulation consisted of a train of five rectangular stimuli of 1 ms duration delivered at 200 Hz. Muscle responses were recorded from 120 pre- to 380 ms post-stimulation. The recorded sEMG signals were sampled at 48 kHz and downsampled to 6 kHz, rectified, band-pass filtered from 10 Hz to 500 Hz and amplified up to 125 times. Between 120 ms pre- and 380 ms post-stimulation, traces for all applied stimulations were automatically saved into separate txt files.

Please consult the README.txt file for details on the structure of the uploaded data and for information w.r.t. potential instances of incompleteness or unusability.

The study was funded by the Swiss National Science Foundation as part of a grant to PS (grant number 320030_179191/1).

The study was registered at clinicaltrials.gov (NCT05031286).