Seasonal changes in blood pressure in chronic kidney disease patients

Background: Seasonal variation in blood pressure ( BP) in different populations has been described. However, no study has concentrated on the change of blood pressure in chronic kidney disease (CKD) patients, a large and growing population worldwide. Furthermore, the role of volume status in seasonal blood pressure variations remains controversial. Methods: 109 CKD patients in a single center were followed between January 1, 2007 and December 31, 2007. Systolic and diastolic blood pressure, level of serum creatinine and body weight were measured in these patients and studied along with climatology data obtained from Beijing Weather Bureau. 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. The seasonal variation of blood pressure in CKD patients appeared not to correlate with CKD stage and similar seasonal variations were observed. Blood pressure values in the cohort of CKD patients were inversely correlated with outdoor temperatures (SBP: r = -0.882, p < 0.001; DBP: r = -0.860, p < 0.001). Furthermore, there was no significant difference in body weight between summer and winter (p > 0.05) in this group of CKD patients. Conclusions: Our results suggest that the blood pressure of CKD patients varied with the seasonal variation. The seasonal variation of blood pressure in CKD patients seemed to have no correlation with stage of CKD or change of body weight but was inversely associated with outdoor temperatures. These results suggested that volume status might not be a key mechanism causing seasonal variation in blood pressure.