Glomerular hyperfiltration is associated with higher nocturnal diastolic blood pressure and with a blunted nocturnal decrease in diastolic blood pressure levels in normotensive and normoalbuminuric IDDM patients.

Abbreviations: CV, coefficient of variation; dBP, diastolic blood pressure; ECG, electrocardiogram; ECV, extracellular volume; GFR, glomerular filtration rate; HF, high frequency; HRV, heart rate variability; LF, low frequency; LF/HF ratio, ratio of power in low-frequency and high-frequency bands; n.u., normalized units; PNN50, the percentage of differences between adjacent R-R intervals Ͼ50 ms; PSA, power spectral analysis; RMSSD, the root mean square of successive differences of adjacent R-R intervals; RRMED, the mean of all R-R intervals; sBP, systolic blood pressure; SDANNi, the SD of the averages of the R-R intervals calculated in 5-min segments; SDNN, the SD of the R-R intervals; SDNNi, the mean of the SD of R-R intervals calculated in 5-min segments; UAER, urinary albumin excretion rate.A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances. RESEARCH DESIGN AND METHODS -A total of 39 normotensive normoalbuminuric type 1 diabetic patients were studied. Glomerular filtration rate ( 51 Cr-EDTA technique), extracellular volume ( 51 Cr-EDTA distribution volume), and urinary albumin excretion rate (UAER) (by radioimmunoassay) were measured. The subjects' 24-h ambulatory blood pressure and a 24-h electrocardiogram were recorded simultaneously. Heart rate variability was calculated in the time domain for 24 h, in the frequency domain at night, at rest in the supine position, and during tilt. Patients were classified according to diastolic blood pressure (dBP) night/day ratio as dipper patients (Յ0.9) and nondipper patients (Ͼ0.9). Autonomic Dysfunction and UrinaryRESULTS -Nondipper patients presented a higher low-frequency (LF) component (a sympathetic index) and higher LF/high-frequency (HF) ratio during sleep than dipper patients (0.29 ± 0.12 vs. 0.19 ± 0.10 normalized units [n.u.], P = 0.008; and 0.98 ± 0.53 vs. 0.55 ± 0.45 n.u., P = 0.007, respectively). At rest, the LF component in nondipper patients (0.38 ± 0.13 n.u.) was higher than in dipper patients (0.27 ± 0.12 n.u., P = 0.04). After the tilt, nondipper patients did not show an increase in the LF component (P = 0.32), but in dipper patients, the increase was significant (P = 0.001). In both groups, tilting promoted a decrease in the HF component (a parasympathetic index). In a stepwise multiple linear regression analysis, the LF component during sleep and the UAER accounted for 24% of the variability in the dBP night/day ratio.CONCLUSIONS -The predominance of sympathetic activity and increased levels of UAER, although within the normal range, are associated with a blunted fall in nocturnal dBP

In this cohort of normoalbuminuric normotensive type 1 diabetic patients, GFR decreased and BP levels increased during the follow-up period. The predictors for the GFR change were baseline GFR level and metabolic control. For end-of-study MBP, the predictor was baseline GFR level.