Abstract WP132: Relationship Of Neck Circumference And Insulin Resistance On The Cerebrovascular Reactivity In Subjects With Obesity.

Abstract

Background: Transcranial doppler (TCD) can be used to detect incipient vascular disease. The breath-holding index (BHI) is a measure of vasomotor reactivity of the brain which can be measured with the TCD. We aim to evaluate the effect of insulin resistance and neck circumference on the cerebrovascular reactivity in subjects with obesity. Methods: BHI was induced by a 30-second apneic stimulus to produce vasodilation in non-diabetic, non-hypertensive individuals with and without obesity (body mass index >35). Neck and abdominal circumference, insulin resistance determined by the HOMA-IR and Matsuda index, scores to detect risk for obstructive sleep apnea (OSA), and cerebrovascular reactivity (BHI) were calculated between the comparison groups. A multivariable linear regression was calculated between the cerebrovascular reactivity with obesity adjusting for insulin resistance indexes, and neck circumference. Neck circumference was considered high when >37 cm in women and >42 cm in men. Results: BHI was measured in 164 right middle cerebral arteries (RMCA) and 152 left MCA (LMCA) of 85 obese patients and 85 non obese individuals. The BHI was significantly lower in the obese individuals: median of 0.83, IQR 0.56-1.21 and 0.89, IQR 0.69-1.11 in the RMCA and LMCA, respectively, vs. median of 1.27, IQR 0.94-1.58 and 1.14, IQR 0.92-1.48 in the RMCA and LMCA (p<0.001) of the non-obese individuals. There was a significant linear association between the HOMA-IR (r 2 0.03, βstd 0.005, p=0.05), the Matsuda index (r 2 0.03, βstd 0.003, p=0.04), and the neck circumference (r 2 0.05, βstd 0.03, p=0.005), and the cerebrovascular reactivity. In the multivariate linear regression model, there was a negative association between the cerebrovascular reactivity and obesity after adjusting for insulin resistance and elevated neck circumference (r 2 0.11, βstd 0.052, p=0.02). Conclusions: We found a diminished vasomotor reactivity in individuals with obesity, which is not explained by insulin resistance or increased neck circumference. Neck circumference showed a more important role in the decrease of cerebrovascular reactivity than the indexes of insulin resistance.