Autonomic dysfunction and circadian blood pressure variations in people with impaired glucose tolerance.

Aims: To assess circadian blood pressure variability in people with impaired glucose tolerance and a healthy control population.

Methods: Seventy-five people with impaired glucose tolerance and 40 healthy volunteers (frequency matched on 10-year age bands and sex) underwent a detailed neurological assessment. Autonomic neuropathy was detected by the five standard cardiovascular autonomic tests and heart rate variability was characterized by the triangle index. Diurnal indices were assessed by 24-h ambulatory blood pressure monitoring. Systolic and diastolic diurnal indices were defined as: (mean daytime blood pressure - mean night-time blood pressure) × 100/mean daytime blood pressure.

Results: Mean 24-h systolic and diastolic blood pressure was significantly higher in the group with impaired glucose tolerance compared with the control group [126 ± 12 (mean ± SD) vs. 117 ± 10, 75 ± 7 vs. 71 ± 6 mmHg, both P < 0.05). Systolic and diastolic diurnal indices and heart rate variability triangular index were significantly lower in people with impaired glucose tolerance compared with control subjects (9.1 ± 7.8 vs. 13.2 ± 5.4, 14.5 ± 9.7 vs. 18.4 ± 7.1 mmHg, 28.0 ± 8.4 vs. 39.5 ± 9.3, all P < 0.05). Differences in mean diastolic blood pressure, heart rate variability triangular index and the frequency of non-dippers between those with impaired glucose tolerance and control subjects seemed to be independent of BMI and the presence of cardiovascular autonomic neuropathy, as simultaneous adjustment for BMI and cardiovascular autonomic neuropathy had no major effect on the results.

Conclusion: Our data suggest that people with impaired glucose tolerance have increased diastolic blood pressure and abnormal circadian blood pressure regulation, independent of obesity and the presence of cardiovascular autonomic neuropathy.