Blood Pressure Seasonality in Hemodialysis Patients from Five European Cities of Different Latitudes

Climate influences the regulation of blood pressure (BP). Our objective was to precisely estimate BP seasonality in hemodialysis (HD) patients from five European cities with marked climate differences.

Stable prevalent HD patients from 5 European facilities (Santa Cruz de Tenerife (Spain), Seville (Spain), Montpellier (France), Ottignies (Belgium), Umea (Sweden)) present over the years 1995-1999 were included in this historical longitudinal observational study. Individual monthly averages of pre-dialysis BP level were computed from all facility BP measurements (> 90 000 observations). The association between BP level and location, seasons and meteorological measurements was analyzed by mixed models.

261 patients were included and followed-up for a median duration of 2 years (6903 monthly observations). Pre-dialysis SBP and DBP were minimal in summer (July) and maximal in winter (November and December), and mean changes were respectively 4.2 [3.0; 5.4] and 2.0 [1.3; 2.7] mmHg. Seasonality was confirmed in 4 locations (Pseason≤0.001 for SBP and DBP), but not in Umea (both Pseason> 0.05). Seasonal changes in DBP were larger in southern locations (Pinteraction=0.02). BP level was associated with climate parameters: in a positive manner with humidity or rainfall, and inversely with sunshine duration or temperature. The effects of temperature and rainfall on DBP varied with latitude (Pinteraction< 0.02) and were greater in southern locations.

BP varies with seasons and climate in different European areas and seasonality can be more important in southern locations. These changes in BP deserve attention as they may be responsible for a significant increase in cardiovascular risk which may be preventable.