One-year aerobic exercise altered cerebral vasomotor reactivity in mild cognitive impairment

Abstract

The purpose of this study was to test the hypothesis that changes in cerebral vasomotor reactivity (CVMR) after 1-yr 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 1-yr 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 ΔCBFV/ΔEtCO₂ and ΔCVCi/ΔEtCO₂. Episodic memory and executive function were assessed using standard neuropsychological tests (CVLT-II and D-KEFS). Cardiorespiratory fitness was assessed by peak oxygen uptake (V̇o_2peak). A total of 37 patients (19 in SAT and 18 in AET) completed 1-yr interventions and CVMR assessments. AET improved V̇o_2peak, increased hypocapnic CVMR, but decreased hypercapnic CVMR. The effects of AET on cognitive performance were minimal when compared with SAT. Across both groups, there was a negative correlation between changes in hypocapnic and hypercapnic CVMRs in CBFV% and CVCi% (r = -0.741, r = -0.725, P < 0.001). Attenuated hypercapnic CVMR, but not increased hypocapnic CVMR, was associated with improved cognitive test scores in the AET group. In conclusion, 1-yr AET increased hypocapnic CVMR and attenuated hypercapnic CVMR which is associated cognitive performance in patients with amnestic MCI.NEW & NOTEWORTHY One-year moderate-to-vigorous intensity aerobic exercise training (AET) improved cardiorespiratory fitness (V̇o_2peak), increased hypocapnic cerebral vasomotor reactivity (CVMR), whereas it decreased hypercapnic CVMR when compared with stretching and toning in patients with amnestic mild cognitive impairment (MCI). Furthermore, changes in hypercapnic CVMR with AET were correlated with improved memory and executive function. These findings indicate that AET has an impact on cerebrovascular function which may benefit cognitive performance in older adults who have high risk of Alzheimer's disease.

Keywords: aerobic exercise training; cerebral vasomotor reactivity; cognitive function; mild cognitive impairment; transcranial Doppler.

Figure 1.

Linear correlations between changes in hypocapnic and hypercapnic cerebral vasomotor reactivity. Cerebral vasomotor reactivity (CVMR) was calculated from the slope of cerebral blood flow velocity (CBFV%) versus end-tidal CO₂ (mmHg) (CBFV/EtCO₂) (top) and cerebrovascular conductance index (CVCi%) versus end-tidal CO₂ (mmHg) (CVCi/EtCO₂) (bottom). Δ represents changes pre- and postinterventions. Solid line, dotted line, and broken line represent those obtained for all subjects, stretching and toning (SAT: 19 subjects) group, and aerobic exercise training (AET: 18 subjects) group, respectively. Bold values represent P < 0.05.

Figure 2.

Linear correlations between changes in peak oxygen uptake (V̇o_2peak), cerebral vasomotor, and cardiovascular reactivity. Cerebral vasomotor reactivity weas calculated from the slope of cerebral blood flow velocity (CBFV%) versus end-tidal CO₂ (mmHg) (CBFV/EtCO₂) (top) and cerebrovascular conductance index (CVCi%) versus end-tidal CO₂ (mmHg) (CVCi/EtCO₂) (middle). Cardiovascular reactivity was calculated from the slope of MAP versus EtCO₂ (mmHg) (MAP/EtCO₂) (bottom). Δ represents changes in pre- and postinterventions. Solid line, dotted line, and broken line represent those obtained for all subjects, stretching and toning (SAT: 19 subjects) group, and aerobic exercise training (AET: 18 subjects) group, respectively. Bold values represent P < 0.05. MAP, mean arterial pressure.

Figure 3.

Linear correlations between changes in hypercapnic cerebral vasomotor reactivity and cognitive performance. Δ represents changes in pre- and postinterventions. Positive change in cognitive score indicates improved cognitive function. Solid line, dotted line, and broken line represent those obtain for all subjects, stretching and toning (SAT: 19 subjects) group, and aerobic exercise training (AET: 18 subjects) group, respectively. Bold values represent P < 0.05.