Seasonal modifications in blood pressure are mainly related to interdialytic body weight gain in dialysis patients

Background. Longitudinal studies in dialysis patients have identified seasonal variations in blood pressure that may follow climatic parameters such as external temperature and humidity. We aimed to assess the participation of interdialytic body weight gain variations in the seasonal profile of blood pressure. Methods. Ninety-nine stable patients (40 F/59 M), 52.9 +/- 1.5 years old, dialyzed in a single satellite dialysis unit between January 7, 1991, and September 30, 1998 were studied. Supine systolic and diastolic blood pressure, body weight, and interdialytic body weight gain were determined at every one of the 3069 dialyses included. and studied along with climatology data obtained from Meteo, France. Results. Blood pressure varied throughout the year, following a cyclic pattern. It increased from the autumn months toward winter, and decreased toward the spring and warmer months. Systolic and diastolic blood pressures were strongly correlated with interdialytic body weight gain (r = 0.925; P < 0.0001 and r = 0.888; P = 0.0001, respectively). Blood pressure was also correlated with the climatic factors: rainfall (r = 0.786;P < 0.003 and r = 0.784: P < 0.003), humidity (r = 0.701; P = 0.011 and r = 0.699: P < 0.012), and day light span (r = -0712; P < 0.01, and r = -0.658: P < 0.02, respectively). Multivariate regression analyses taking blood pressure as a dependent variable retained interdialytic body weight gain as the first variable in the model. Conclusion. Our results establish a strong link between blood pressure variations and interdialytic body weight gain, showing the important participation of volume state in modulating blood pressure in this group of patients.