DIFFERENTIAL GLUCOSE-TOLERANCE IN DIPPER AND NONDIPPER ESSENTIAL-HYPERTENSION - THE IMPLICATIONS OF CIRCADIAN BLOOD-PRESSURE REGULATION ON GLUCOSE-TOLERANCE IN HYPERTENSION

OBJECTIVE - The goals of this study were to compare glucose tolerance in dipper and nondipper hypertensive patients and to explore the cause of glucose intolerance in essential hypertension. RESEARCH DESIGN AND METHODS - A total of 50 patients <45 years old who had essential hype rtension were recruited and studied by 24-h blood pressure monitoring and an oral glucose tolerance test (OGTT). Autonomic function was asse ssed with spectral analysis of heart rate variability. RESULTS - Dippe r hypertensive patients (n = 25) had lower nocturnal blood pressure th an nondipper (n = 25) patients. During OGTT, postprandial glucose leve ls were higher in the nondippers at 0, 90, and 120 min (all P < 0.05). Nondippers had a higher fasting insulin/glucose ratio than was appare nt in normal control subjects. Despite higher postprandial glucose lev els, nondippers had lower postprandial insulin levels. These results s uggest that nondippers were insulin resistant and that their pancreati c beta-cell function was impaired. For all patients, nocturnal reducti on of blood pressure was inversely related to total glucose levels und er the OGTT curve and was positively related to postprandial insulin l evels. Daytime heart rate did not differ between the dippers and nondi ppers, but nocturnal heart rate was higher in the nondippers, suggesti ng that nocturnal sympathetic activities were higher among the nondipp ers. Spectral analysis of heart rate variability suggests that the non dippers had lower parasympathetic activities and unbalanced sympatheti c/parasympathetic outflow. CONCLUSIONS - These findings indicate that nondipper hypertensive patients are more glucose intolerant than are d ipper patients. The abnormalities of glucose metabolism in nondippers could be explained by insulin resistance and beta-cell dysfunction. Th e results of spectral analysis suggest that abnormal autonomic outflow may represent a possible link between hypertension and associated met abolic dysfunction.