Ambulatory Blood Pressure in Type I Diabetes Mellitus: Comparison to Presence of Incipient Nephropathy in Adolescents and Young Adults

Abstract

AMBP measurements were obtained at 20-min intervals during the day and at 60-min intervals during the night in 38 adolescents and young adults (12–25 yr old) with type I diabetes, and in 36 healthy, nondiabetic control subjects of comparable age. The group of patients with elevated AER (>15 μg/min) had higher mean 24-h sBP, dBP, and BPB (defined as the prevalence of systolic readings >130 mm Hg or diastolic readings >85 mm Hg) compared with both the group of patients with type I diabetes and AER<15, and the control group. The normal diurnal variation in BP and BPB was observed in the control group and the group with type I diabetes and AER<15, whereas the nocturnal decrease observed in the group with type I diabetes and AER>15 was not statistically significant. Elevations in AMBP of the patient group with AER>15 were reflected in random BP measurements. Even though the mean random BP measurements of all groups were within the normal range for age, the mean random sBP and dBP of the type I diabetes patients with AER>15 was higher than both the control group and the group with type I diabetes and AER<15. The GFR, determined by the clearance of ⁹⁹Tc-DTPA, was associated negatively with measures of AMBP and AER in the group with AER>15. The mean 24-h sAMBP, dAMBP, and BPB of the type I diabetes patients with AER<15 were elevated compared with the control group. The mean random sBP of the type I patients with AER<15 was not significantly different from the control group, whereas the mean random dBP of this group was significantly greater than the control group. Significant overlap in the BPs and BPBs occurred among the groups, but the mean 24-h sBP and BPBs were above the 90th percentile for control subjects in most type I diabetes patients with AER<15 and in ∼50% of type I diabetes patients with AER<15. The three groups separated across the age range (12–25 yr old) for the different measures of AMBP. We conclude that AMBP measurement is useful in detecting abnormalities in BP that are not apparent in random BP measurement in patients with onset of type I diabetes before puberty and no evidence of early diabetic nephropathy. These findings may be important in identifying individuals who either are susceptible to the development of diabetic nephropathy or have early renovascular dysfunction not apparent in AER>15. AMBP measurement may be useful in monitoring interventions designed to prevent or delay the development of diabetic nephropathy.