CEREBRAL OXYGENATION/PERFUSION, CARDIAC HEMODYNAMICS DURING EXERCISE AND COGNITIVE FUNCTIONS IN OBESE PATIENTS

Abstract

Obesity is associated with an accelerated rate of cognitive decline in memory, attention, processing speed and executive functions resulting in a higher risk of dementia and Alzheimer’s disease (AD) in later life. In cardiac patients showing mild cognitive impairments, cerebral O2Hb correlates with VO2 peak and left ventricular ejection fraction, reflecting a link between cardiac output and cerebral O2Hb during maximal exercise. Objectives:1) To compare cerebral oxygenation/perfusion (COP), central hemodynamics, VO2 peak and cognitive functions in obese patients (OB) and age-matched healthy controls (AMHC) 2) to study the relationships between VO2 peak, cardiac output (CO),cognitive functions in OB. 21 AMHC and 33 OB subjects were recruited. VO2 peak (ml/min/LBM), cardiac hemodynamics (impedance cardiography) and COP (near-infrared spectroscopy) were measured during a maximal incremental ergocycle test. Cognitive function assessments (standard battery, paper-pen tests) included: short term-working memory, perceptual abilities, processing speed, inhibition and mental flexibility and long-term verbal memory. Compared to AMHC, OB had a lower VO2 peak, lower ejection fraction (EF%), and higher end-systolic and end-diastolic volume indexes (P<0.05), but the ΔHHb was lower in OB (P<0.05). Cognitive function was similar between groups when defining obesity as % body fat. VO2 peak was related to cognitive functions (short term-working memory, processing speed, inhibition and mental flexibility: R=-0.32 to 0.43, P<0.05) but not cardiac index (CI). 1) OB subjects have a lower VO2 peak (including VO2 peak adjusted for lean body mass) compared to AMCH, indicating lower cardiorespiratory fitness. 2) Cognitive function was similar between groups when defining obesity as % body fat. However, visceral adiposity defined by % of trunk fat mass correlated significantly with short-term memory(Forward Empan), inhibition and mental flexibility (stroop 3 and stroop 4). 3) Because of similar ΔO2Hb during exercise between groups and because ΔHHb (mM) was significantly reduced in OB, these results suggest a reduced O2Hb extraction in OB. However, reduced ΔHHB in OB was not associated with impaired cognitive function. 4) In all subjects, parameters assessing the main executive functions were correlated to VO2 peak but not the CO or CI.