The purpose of this study was to test the hypothesis that changes in cerebral vasomotor reactivity (CVMR) after one-year aerobic exercise training (AET) are associated with cognitive performances in individuals with amnestic mild cognitive impairment (MCI). Seventy sedentary patients with amnestic MCI were randomized to one-year moderate to vigorous intensity AET or stretching and toning (SAT) interventions. Cerebral blood flow velocity (CBFV) with transcranial Doppler, mean arterial pressure (MAP) with finapres plethysmograph, and EtCO2 with capnography were measured during hyperventilation (hypocapnia) and a modified rebreathing protocol (hypercapnia) to assess CVMR. Cerebrovascular conductance index (CVCi) was calculated by CBFV/MAP, and CVMR by deltaCBFV/deltaEtCO2 and deltaCVCi/deltaEtCO2. Episodic memory and executive function were assessed using standard neuropsychological tests (CVLT-II and D-KEFS). Cardiorespiratory fitness was assessed by peak oxygen uptake (VO2peak). A total of 37 patients (19 in SAT and 18 in AET) completed one-year interventions and CVMR assessments. AET improved VO2peak, increased hypocapnic CVMR, but decreased hypercapnic CVMR. AET effects on cognitive performance were minimal when compared with SAT. Across both groups, there was a negative correlation between changes in hypo- and hypercapnic CVMRs in CBFV% and CVCi% (r = -0.741, r = -0.725, p < 0.001). Attenuated hypercapnic CVMR, but not increased hypocapnic CVRM, was associated with improved cognitive test scores in the AET group. In conclusion, one-year AET increased hypocapnic CVMR and attenuated hypercapnic CVMR which is associated cognitive performance in patients with amnestic MCI.

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