ON THE MECHANISMS OF BLUNTED NOCTURNAL DECLINE IN ARTERIAL BLOOD-PRESSURE IN NIDDM PATIENTS WITH DIABETIC NEPHROPATHY

Nondiabetic hypertensive patients lacking the normal nocturnal decline in arterial blood pressure have enhanced cardiovascular complications . Since cardiovascular morbidity and mortality are increased in non-in sulin-dependent diabetes mellitus (NIDDM), we performed a prospective cross-sectional case-controlled study comparing the diurnal variation in arterial blood pressure, prevalence of dippers, cardiac autonomic n ervous function (beat-to-beat variation during deep breathing), and ex tracellular fluid volume (Cr-51-labeled EDTA) in 55 NIDDM patients wit h diabetic nephropathy (group 1), 55 NIDDM patients with normoalbuminu ria (group 2), and 22 nondiabetic control subjects (group 3). All anti hypertensive treatments were withdrawn at least 2 weeks before the stu dy. The nocturnal blood pressure reduction (daytime-to-nighttime)/dayt ime (mean +/- SE) was impaired in group I (6.6 +/- 1.5%) and group 2 ( 11.1 +/- 1.4%) as compared with group 3 (17.6 +/- 1.7%), and it was im paired in group 1 as compared with group 2 (P < 0.05 for each comparis on). The prevalence of dippers (95% confidence interval) was lower in group 1 (42% [29-56]) as compared with group 2 (58% [44-71]; P = 0.08) and group 3 (86% [65-97]; P < 0.001) and in group 2 as compared with group 3 (P < 0.01). Abolished beat-to-beat variation was more prevalen t in group 1 (63% [50-76]) as compared with group 2 (15% [7-27]) and w ith group 3 (5% [0-23]) (P < 0.001). Nocturnal blood pressure reductio n was associated with beat-to-beat variation during deep breathing (r = 0.22, P < 0.01). Extracellular fluid volume (mean +/- SE) was higher in group 1 (15.9 +/- 0.5 l/m(2)) as compared with group 3 (14.1 +/- 0 .8 l/m(2)) (P < 0.05) with group 2 between the two (15.1 +/- 0.4 l/m(2 )). Extracellular fluid volume was not associated with the degree of n octurnal blood pressure reduction. in conclusion, NIDDM patients with and without diabetic nephropathy have blunted nocturnal decline in art erial blood pressure, a condition that might enhance the strain on the microvascular and cardiovascular system. The high prevalence of auton omic neuropathy may also contribute to the increase cardiovascular mor bidity and mortality characteristically found in these patients.