Blunted cerebral vascular responsiveness to hypercapnia in obese individuals

Abstract

Obesity increases the risk of cardiovascular disease (CVD) by more than 45%. Furthermore, obesity is a contributing factor for cognitive impairment and Alzheimer disease. The mechanisms accounting for this increased disease risk have not been clarified. This study tested the hypothesis that the total range of change (a) in cerebral blood velocity (CBV) and cerebral vascular conductance (CVCI) as well as maximum (y0) CBV and CVCI achieved during rebreathing-induced hypercapnia would be attenuated in obese individuals (obese). 16 lean and 15 obese individuals participated. The magnitude of rebreathing-induced hypercapnia was similar between groups (Lean: ∆ 15 ± 3 mmHg vs. Obese ∆ 15 ± 2 mmHg; P = 0.82). The total range of change in CBV during rebreathing (a; percentage) was similar between groups (Lean: 91 ± 24 % vs. Obese: 76 ± 19 %, P = 0.07) whereas the total range of change in CVCI during rebreathing (a; percentage) was attenuated in the Obese (Lean: 71 ± 20 % vs. Obese: 51 ± 15 %, P < 0.01). Likewise, the maximal increase in CBV during rebreathing (y0; percentage) was similar between groups (Lean: 189 ± 22 % vs. Obese: 179 ± 20 %, P = 0.20) whereas the maximal increase in CVCI during rebreathing (y0; percentage) was attenuated in the Obese (Lean: 172 ± 19 % vs. Obese: 155 ± 17 %, P = 0.01). These data indicate that cerebral vascular response to rebreathing-induced hypercapnia is attenuated in obese individuals. This impairment may be a contributing factor for the elevated cerebral vascular / neurocognitive disease risk in this population.

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