Ambulatory blood pressures and autonomic nervous function in normoalbuminuric type I diabetic patients.

BACKGROUND In insulin-dependent diabetes mellitus (IDDM) patients with normal urinary albumin excretion (UAE) controversy exists about the presence of blood pressure (BP) elevation and an attenuation of BP decline during sleep. SUBJECTS AND METHODS These issues were studied in 60 IDDM patients and 55 healthy control subjects with 24 h ambulatory blood pressure monitoring. In addition, in the IDDM patients two cardiovascular reflex tests were performed to study autonomic nervous function. RESULTS 55 IDDM patients had 4.4/3.1 mm Hg higher 24 h systolic/diastolic pressures when compared with 55 healthy matched controls (P = 0.005/0.009). The diastolic BP decline during sleep was significantly attenuated in IDDM patients compared to healthy volunteers (18.9 vs 22.2%, P = 0.01). The maximum/minimum (max/min) ratio of the RR' interval of the lying to standing test (lower values indicating (incipient) parasympathetic dysfunction) was positively related to the decline of the diastolic BP during sleep in the diabetic patients. This relationship did not persist after adjusting for decline of heart rate during sleep. CONCLUSIONS IDDM patients with normal UAE, compared with healthy control subjects, have higher BPs during both the waking and sleeping periods and a decreased diastolic BP decline during sleep. In these patients both the diastolic BP decline and the heart rate decline during sleep were related to the max/min ratio. These findings are consistent with the hypothesis that attenuation of diastolic BP decline during sleep is at least partly due to (incipient) damage to the parasympathetic nervous system, which, through a blunted heart rate decline, leads to a decreased decline of cardiac output during sleep.