Selected climatic variables and blood pressure in Central European patients with chronic renal failure on haemodialysis treatment.Blood Press. 2005; 14(2):86-92.BP
BACKGROUND/AIMS;Higher blood pressure (BP) in winter has been documented in healthy and hypertensive adults. It may potentially contribute to the observed excess winter cardiovascular mortality in the general population. The aim of the study was to assess whether BP varies similarly among patients with chronic renal failure on haemodialysis treatment, who present an increased risk of cardiovascular death.
We retrospectively analysed values of pre-dialysis BP and parameters of fluid retention--pre-dialysis body weight and inter-dialytic weight gain measured in 49 patients (23 male, 26 female; aged 46.0+/-13.5 years) from 1995 to 1998. For each patient we calculated deviations of monthly mean values of systolic BP, diastolic BP, pre-dialysis body weight and inter-dialytic weight gain from the lowest monthly means of these parameters in a given year. Monthly means of these deviations for the whole study group (dSBP, dDBP, dBW, dWG, respectively) were subsequently computed. Monthly means of air temperature (T), air relative humidity (H) and atmospheric pressure (AP) were provided by the local Institute of Meteorology. The Wilcoxon paired test was applied to compare mean values of BPs and parameters of fluid retention of every patient in three warmest and three coldest months of each year. Spearman rank correlation analysis was employed to evaluate relationships between dSBP, dDBP and climatic variables, dBW or dWG.
Systolic BP was higher in summer than in winter (146.6+/-20.5 vs 143.4+/-18.9 mmHg; p<0.00001). Diastolic BP was also higher in summer than in winter (82.6+/-8.5 vs 79.6+/-7.3 mmHg; p<10(-9)). Pre-dialysis body weight and inter-dialytic weight gain did not differ between summer and winter (66.0+/-13.2 vs 66.0+/-13.2 kg; p=0.98 and 2.27+/-0.6 vs 2.29+/-0.5 kg; p=0.53). There was a positive correlation between dSBP and T (RS=0.424, p<0.003), as well as dDBP and T (RS=0.591, p<0.00001) and an inverse correlation between dSBP and H (RS=-0.372, p<0.01), as well as dDBP and H (RS=-0.408, p<0.004). There were no significant associations between BPs and AP, dBW or dWG.
In haemodialysed patients from southern Poland, BP is higher in summer than in winter. Changes in BP are related to seasonal changes in climatic variables--air temperature and air relative humidity. Seasonal variation in BP is not associated with variation in fluid retention. Possible alteration of cardiovascular reactivity to changes in climatic environment in haemodialysed chronic renal failure patients may be one of the potential explanations of these observations.