Many factors contribute to the regulation of blood pressure. The role of climate has received relatively little attention. During a four-year period, we determined the influence of climate on blood pressure in 53 patients with end-stage renal disease treated with hemodialysis. For each patient, blood pressure was measured before each of three dialysis treatments per week for an average of 31 months. The dose of dialysis (urea clearance multiplied by the length of dialysis and divided by the distribution volume of urea) and protein catabolism rate were assessed monthly. We then analyzed the monthly mean values for blood pressure, pulse, and body weight in relation to the monthly values for temperature, relative humidity, and atmospheric pressure recorded in Montpellier, France. The maximal monthly temperature varied from 10 degrees C in the winter to 31 degrees C in the summer, and the minimal monthly temperature from 1 degree to 20 degrees C. The mean (+/-SE) systolic and diastolic blood pressure was highest during the winter (153+/-3/82+/-2 mm Hg) and lowest during the summer (141+/-3/75+/-2 mm Hg). The seasonal pattern was evident throughout the four-year period. Blood pressure was correlated inversely with monthly maximal temperature (r= -0.65 and P<0.001 for systolic pressure; r= -0.71 and P<0.001 for diastolic pressure) and directly with minimal humidity (r=0.45 and P=0.002 for systolic pressure; r=0.43 and P=0.003 for diastolic pressure). Changes in protein catabolic rate, weight gain during dialysis, and dialysis dose were not related to changes in blood pressure. In patients with end-stage renal disease treated with hemodialysis, blood pressure varies seasonally, with higher values in the winter and lower values in the summer.
