LOSS OF THE NOCTURNAL DIP AND INCREASED VARIABILITY OF BLOOD-PRESSURE IN NORMOTENSIVE PATIENTS WITH NONINSULIN-DEPENDENT DIABETES-MELLITUS

Eleven normotensive diabetics with noninsulin-dependent diabetes mellitus (NIDDM) (mean age 52.5 +/- SD 8.2 years) and 11 controls (mean age 47.4 +/- SD 8-9 years) had their ambulatory blood pressure and heart rate recorded non-invasively by the Oxford Medilog System in standard hospital conditions. The results were averaged as hourly means of systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), and heart rate (HR) for the 24-h period and similarly for the 'awake' period (14-16 h) and the 'asleep' period (8-10 h). Hourly means for diabetics and controls showed no differences in blood pressure and heart rate over the 24 h. During sleep, control subjects showed a significant drop in SBP (P<0.001), DBP (P<0.001), MAP (P<0.001) and HR (P<0.001). However, this nocturnal dip in blood pressure could not be demonstrated in the diabetic group. Blood pressure variability was significantly increased in diabetics compared to controls during waking hours (P<0.01). These results indicate that in noninsulin-dependent diabetics during sleep there is loss of the nocturnal dip of BP seen in normal subjects, and they have increased BP variability. These may be contributing factors to the development of hypertension and the accelerated target organ damage (TOD) seen in diabetes.