Are psoriatic patients at risk of heat intolerance?

Sixteen young male subjects with psoriasis (mean of 4.9% of skin surface area involvement) and 10 healthy controls underwent a heat exercise test (40 degrees C, 40% r.h.) for 2 h. Rectal temperature (Tr), mean skin temperature (Tsk), heart rate (HR) and heat storage (dS) were measured and calculated. A sharper rise was found for all parameters in the psoriatic patients as compared with controls. Statistically significant differences were found in Tr after 60 min (37.9 +/- 0.1 degrees C and 37.5 +/- 0.1 degrees C in patients and controls, respectively) and at termination of the exercise (38.3 +/- 0.1 degrees C and 37.5 +/- 0.1 degrees C). Heat storage at the end of the first hour was 78 +/- 9 and 30 +/- 7 kcal in patients and controls, respectively. At the end of 120 min, heat storage in the study group increased to 87 +/- 14 kcal, while the control group stored only 30 +/- 7 kcal. Sweat rate was lower in the psoriatic patients (590 +/- 49 g/h) than in controls (691 +/- 42 g/h), even when corrected for healthy skin area (337 +/- 26 g/h/m2 compared with 370 +/- 24 g/h/m2). It is suggested that psoriatic patients have a reduced ability to dissipate extra heat during exposure to exercise in the heat. Psoriasis should therefore be considered as a risk factor for heat intolerance.