Key result
Diabetic subjects with autonomic abnormalities had significantly reduced low-frequency power compared to controls (5.95 vs 6.73 ln-msec2, p<0.001), indicating altered circadian sympathovagal balance.
Why the study?
Does diabetes alter the circadian modulation of sympathovagal activity compared to healthy controls?
Case-Control (n=108)
Does diabetes alter the circadian modulation of sympathovagal activity compared to healthy controls?
Absolute Event Rate: 5.95% vs 6.73%
p-value: p=<0.001
Diabetic patients exhibit impaired circadian modulation of sympathovagal balance, with decreased vagal and relatively higher sympathetic activity at night, potentially explaining their altered temporal onset of cardiovascular events.
May link autonomic imbalance to shifted CV event timing in diabetes; hypothesis-generating and requires prospective validation.
BACKGROUND: Diabetic subjects have a high incidence of cardiovascular accidents, with an altered circadian distribution. Abnormalities in the circadian rhythm of autonomic tone may be responsible for this altered temporal onset of cardiovascular disease. METHODS AND RESULTS: To assess circadian changes of sympathovagal balance in diabetes, we performed 24-hour power spectral analysis of RR interval fluctuations in 54 diabetic subjects (age, 44 +/- 2 years) with either normal autonomic function or mild to severe autonomic neuropathy and in 54 age-matched control subjects. The power in the low-frequency (LF, 0.03-0.15 Hz) and high-frequency (HF, 0.18-0.40 Hz) bands was considered an index of relative sympathetic and vagal activity, respectively. Diabetic subjects with autonomic abnormalities showed a reduction in LF compared with control subjects (5.95 +/- 0.12 In-msec2 versus 6.73 +/- 0.11, p < 0.001) and an even greater reduction in LF, particularly during the night and the first hours after awakening (5.11 +/- 0.18 In-msec2 versus 6.52 +/- 0.14, p < 0.001). Day-night rhythm in sympathovagal balance was reduced or absent in diabetic subjects compared with control subjects. CONCLUSIONS: Diabetic subjects with or without signs of autonomic neuropathy have a decreased vagal activity (and hence a relatively higher sympathetic activity) during night hours and at the same time of the day, during which a higher frequency of cardiovascular accidents has been reported. These observations may provide insight into the increased cardiac risk of diabetic patients, particularly if autonomic neuropathy is present.
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Bernardi et al. (1992) conducted a case-control in Diabetes (n=108). Diabetes vs. Age-matched control subjects was evaluated on Low-frequency (LF) power (p=<0.001). Diabetic subjects with autonomic abnormalities had significantly reduced low-frequency power compared to controls (5.95 vs 6.73 ln-msec2, p<0.001), indicating altered circadian sympathovagal balance.
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