BACKGROUND:

Cardiovascular autonomic neuropathy (CAN) has been thought to underlie the loss of normal nocturnal blood pressure dipping, which is associated with a higher risk for nephropathy in Type 1 diabetes. Previous analyses also suggest however that nephropathy is a major predictor of subsequent CAN.

OBJECTIVE:

To investigate links between non-dipping phenomenon (NDP) and complications, particularly CAN and nephropathy.

METHODS:

24-h ambulatory blood pressure monitoring was performed on 61 consecutively recruited subjects (mean age: 38.5+/-8.1, mean duration: 29.5+/-8.2 years) from the Pittsburgh Epidemiology of Diabetes Complications cohort (658 subjects with childhood onset Type 1 diabetes diagnosed between 1950 and 80). NDP was diagnosed if nocturnal fall of both systolic and diastolic blood pressure was <10% of the average daytime blood pressure. CAN was detected by abnormal (<or=1.1) expiration/inspiration heart rate ratio. Proteinuria was established by abnormal (>20 microg/min) albumin excretion rate (AER) in at least two of three timed urines.

RESULTS:

Non-dippers (n=17) had greater LDLc (p=0.012) and AER (p=0.052) and a higher frequency of nephropathy (OR=3.6, 95% CI=1.0-12.6) and proliferative retinopathy (OR=5.1, 95% CI=1.3-20.3) compared to the 44 dippers. CAN and NDP were not associated. In multivariate analyses, adjusting for CAN, proteinuria was significantly related to NDP (OR=3.6, 95% CI=1.0-12.6), an association that further modeling suggests was related to interactions between nephropathy, LDLc and hypertension.

CONCLUSIONS:

These data suggest a strong link between NDP and proteinuria which is independent of CAN and may be modified by LDLc and hypertension.