Pain tolerance after stroke: The Tromsø study.

BACKGROUND: Stroke lesions might alter pain processing and modulation by affecting the widely distributed network of brain regions involved. We aimed to compare pain tolerance in stroke survivors and stroke-free persons in the general population, with and without chronic pain. METHODS: We included all participants of the sixth and seventh wave of the population-based Tromsø Study who had been tested with the cold pressor test (hand in cold water bath, 3°C, maximum time 106 s in the sixth wave and 120 s in the seventh) and who had information on previous stroke status and covariates. Data on stroke status were obtained from the Tromsø Study Cardiovascular Disease Register and the Norwegian Stroke Register. Cox regression models were fitted using stroke prior to study attendance as the independent variable, cold pressor endurance time as time variable and hand withdrawal from cold water as event. Statistical adjustments were made for age, sex, diabetes, hypertension, hyperlipidaemia, body mass index and smoking. RESULTS: In total 21,837 participants were included, 311 of them with previous stroke. Stroke was associated with decreased cold pain tolerance time, with 28% increased hazard of hand withdrawal (hazard ratio [HR] 1.28, 95% CI 1.10-1.50). The effect was similar in participants with (HR 1.28, 95% CI 0.99-1.66) and without chronic pain (HR 1.29, 95% CI 1.04-1.59). CONCLUSIONS: Stroke survivors, with and without chronic pain, had lower cold pressor pain tolerance, with possible clinical implications for pain in this group. SIGNIFICANCE: We found lower pain tolerance in participants with previous stroke compared to stroke-free participants of a large, population-based study. The association was present both in those with and without chronic pain. The results may warrant increased awareness by health professionals towards pain experienced by stroke patients in response to injuries, diseases and procedures.

Physical activity and cold pain tolerance in the general population.

BACKGROUND: The relationship between habitual physical activity (PA) and experimental pain tolerance has been investigated in small samples of young, healthy and/or single-sex volunteers. We used a large, population-based sample to assess this relationship in men and women with and without chronic pain. METHODS: We used data from the sixth and seventh Tromsø Study surveys (2007-2008; 2015-2016), with assessed pain tolerance of participants with the cold pressor test (CPT: dominant hand in circulating cold water at 3°C, maximum test time 106 s), and self-reported total amount of habitual PA in leisure time (n = 19,087), exercise frequency (n = 19,388), exercise intensity (n = 18,393) and exercise duration (n = 18,343). A sub-sample had PA measured by accelerometers (n = 4,922). We used Cox regression to compare CPT tolerance times between self-reported PA levels. For accelerometer-measured PA, we estimated hazard ratios for average daily activity counts, and for average daily minutes of moderate-to-vigorous PA done in bouts lasting 10 min or more. Models were tested for PA-sex, and PA-chronic pain and PA-moderate-to-severe chronic pain interactions. RESULTS: Leisure-time PA, exercise intensity and exercise duration were positively associated with CPT tolerance (p < .001; p = .011; p < .001). More PA was associated with higher CPT tolerance. At high levels of leisure-time PA and exercise intensity, men had a significantly higher CPT tolerance than women. Accelerometer-measured PA was not associated with CPT tolerance. CONCLUSIONS: This study is one of the first to show that higher self-reported habitual PA was connected to higher experimental pain tolerance in a population-based sample, especially for men. This was not found for accelerometer-measured PA. SIGNIFICANCE: This study finds that higher level of self-reported leisure-time physical activity is associated with increased cold pressor pain tolerance in a large population-based sample. Though present in both sexes, the association is strongest among men. Despite the robust dose-response relationship between pain tolerance and self-reported activity level, no such relationship was found for accelerometer-measured activity, reflecting a possible discrepancy in the aspect of physical activity measured. Though the study design does not permit causal conclusions, the findings suggest that increasing physical activity may increase pain tolerance in the general population.