Blood pressure is correlated with vitamin d(3) serum levels in dialysis patients

The blood pressure, the most influencing factor in cardiovascular disease in end-stage renal failure patients, follows a seasonal variation during the year. Since vitamin D(3) is known to be related to sun exposure, we wanted to evaluate the putative participation of the vitamin D(3) metabolism in blood pressure modifications.

We studied 22 stable hemodialysis patients (11 females and 11 males, mean age +/- SD 56 +/- 1 year) who had been continuously treated in our dialysis unit for more than 1 year between 1994 and 1997 and did not receive pulse vitamin D(3) treatment. Supine systolic and diastolic blood pressures were measured before every dialysis session (>12,000 measurements) and the intact parathormone (iPTH), 25-hydroxyvitamin D(3) [25(OH)D(3)], and 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] levels every 3 months (>300 determinations). The mean values of blood pressure per season and per patient were taken for analysis using a 4-year longitudinal study design.

The blood pressure varied during the years studied following a seasonal trend. It was highest during autumn and tended to decrease during spring and warmer months. Systolic as well as diastolic blood pressures were significantly correlated with the 25(OH)D(3) levels (p = 0.0291 and p = 0.0327, respectively). No correlation was observed between blood pressure and 1,25(OH)(2)D(3) or iPTH levels.

There is a link between blood pressure and 25(OH)D(3) level. This interrelation is not secondary to a iPTH modulation. Although it cannot be excluded that vitamin D(3) and blood pressure vary following a third factor with seasonal variations, since vitamin D(3) varies during the year, mainly following sun exposure, we suggest that vitamin D(3) is one of the factors participating in the seasonal variation of the blood pressure. Other factors known to control the blood pressure and particularly the extracellular volume overload may also participate.