Background: Abnormalities of the systemic blood pressure are closely associated with the development of diabetic nephropathy. Our aim was to examine the relationship between diurnal blood pressure pattern and albuminuria in insulin-dependent normotensive diabetic patients before the development of overt nephropathy.
Methods: Urinary albumin excretion rates were determined by radioimmunoassay, and 24-h ambulatory blood pressure monitoring was performed. Means and diurnal index was calculated for systolic, diastolic and mean arterial blood pressure, for day-time, night-time, and the whole day. The results of the normoalbuminuric (n = 39) and microalbuminuric (n = 29) groups are compared, and correlation of the blood pressure parameters with albuminuria is analysed.
Results: Twenty-four hours and night-time mean blood pressures were significantly higher, diurnal indices characterizing the night-time blood pressure drop were smaller in the microalbuminuric group. With multiple regression analysis a significant positive correlation was found between albumin excretion rates and 24-h mean systolic blood pressure and a significant negative correlation between albumin excretion rates and the diurnal index of mean arterial pressure (r2= 0.40, P<0.0001). In the normoalbuminuric group 1 (2.6%) patient, in the microalbuminuric group 7 (24.1%/) were 'non-dippers'.
Conclusion: We conclude that in normotensive insulin-dependent diabetic patients the night-time decrease of blood pressure is smaller if microalbuminuria is present. Higher nocturnal blood pressure load is associated with the increase of albuminuria, even before the onset of overt diabetic nephropathy or hypertension.