Effect of ambient cold exposure on pain modulation: exploring individually reported thermal comfort as moderating...

Pain is a hallmark of musculoskeletal conditions. Some studies suggest that pain is exacerbated by working in cold environments, potentially due to poorly understood mechanisms within the somatosensory system. The aim of this study was to assess whether ambient cold exposure influences the efficiency of endogenous pain inhibition and the potential role of subjective thermal comfort.

In a crossover study with 1 week interval and in randomized order, 20 healthy men were exposed to cold (COLD; 10 °C) and thermoneutral (TN; 22 °C) conditions in a controlled environment room (CER) for 2 h. Conditioned pain modulation (CPM), defined as the difference in mean rated pain of a test stimuli (TS) with and without a conditioning stimulus (CS), was calculated before and after CER. Test stimuli (TS) was a 30 s tonic noxious heat stimulation to the dominant volar forearm, and conditioning stimuli (CS) was immersion of the contralateral hand in water holding 4 °C. Subjective TS pain was rated on a 0-10 cm computerized Visual Analogue Scale (VAS). Thermal comfort, encompassing subjective thermal perception, evaluation, and preference, was assessed using standardized subjective judgment scales.

The CPM-effect was significantly reduced by COLD exposure, but not by TN exposure. As expected, participants' ratings of thermal comfort changed across exposure conditions; however, this had no significant influence on the CPM-effect.

Exposure to cold ambient conditions impaired endogenous pain-inhibitory pathways, an outcome not observed under thermoneutral conditions. Furthermore, the results suggest that thermal comfort does not influence endogenous pain-inhibitory pathways. Further research is required to identify moderators affecting pain processing in cold working environments. Regional Ethics Committee, Norway (REK sør-øst C; application # 2017/1859).