Is reduced baroreflex gain a component of the metabolic syndrome? Insights from the LINOSA study

J Hypertens. 2006 Feb;24(2):361-70. doi: 10.1097/01.hjh.0000202817.02836.9c.

Abstract

Objective: To assess the relationship between insulin resistance and baroreflex gain (BRS) in the context of the metabolic syndrome.

Design: Observational population study.

Patients: We studied the healthy population of a small Mediterranean island (Linosa, about 0.5 square miles, 450 inhabitants) where genetic, psychosocial and behavioral bias is likely to be minimal for historical and social reasons.

Measures: Baroreflex gain (BRS, by the frequency domain alpha index) and indices of autonomic regulation of the sino-atrial (SA) node derived from spectral analysis of RR interval variability were obtained, together with metabolic and behavioral indicators in the 144 participating subjects (age range 20-82 years). Carotid artery thickness (CCA) was also obtained with computer-aided ultrasound techniques. Insulin resistance was estimated by the homeostasis model assessment (HOMA), and subjects divided in tertiles accordingly.

Results: BRS appeared to be reduced progressively with increasing levels of HOMA (respectively, 21.0 +/- 2.6, 17.7 +/- 1.7, 15.7 +/- 1.9 ms/mmHg, P < 0.03), while spectral indices of autonomic SA regulation appeared to be only insignificantly affected. Conversely, CCA was significantly increased with increasing HOMA (P < 0.024). Furthermore, BRS appeared to be significantly correlated with various elements of the metabolic syndrome, with CCA and abdominal obesity showing the strongest link.

Conclusions: In an otherwise healthy population, BRS, but not spectrally derived indices of SA node autonomic regulation, are progressively reduced with increasing severity of insulin resistance, possibly as a consequence of attendant carotid artery thickening.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Autonomic Nervous System / physiopathology
  • Baroreflex / physiology*
  • Female
  • Humans
  • Insulin Resistance / physiology*
  • Male
  • Middle Aged
  • Sinoatrial Node / physiology