Cerebral perfusion, oxygenation and metabolism during exercise in young and elderly individuals

Key points center dot The influence of normative ageing on cerebral perfusion, oxygenation and metabolism during exercise is not well known. center dot This study assessed cerebral perfusion and concentration differences for oxygen, glucose and lactate across the brain, in young and elderly individuals at rest and during incremental exercise to exhaustion. center dot We observed that during submaximal exercise (at matched relative intensities) and during maximal exercise, cerebral perfusion was reduced in older individuals compared with young individuals, while the cerebral metabolic rate for oxygen and uptake of glucose and lactate were similar. center dot The results indicate that the age-related reduction in cerebral perfusion during exercise does not affect brain uptake of lactate and glucose. Abstract We evaluated cerebral perfusion, oxygenation and metabolism in 11 young (22 +/- 1 years) and nine older (66 +/- 2 years) individuals at rest and during cycling exercise at low (25%Wmax), moderate (50%Wmax), high (75%Wmax) and exhaustive (100%Wmax) workloads. Mean middle cerebral artery blood velocity (MCA Vmean), mean arterial pressure (MAP), cardiac output (CO) and partial pressure of arterial carbon dioxide () were measured. Blood samples were obtained from the right internal jugular vein and brachial artery to determine concentration differences for oxygen (O2), glucose and lactate across the brain. The molar ratio between cerebral uptake of O2versus carbohydrate (O2carbohydrate index; O2/[glucose +1/2 lactate]; OCI), the cerebral metabolic rate of O2 (CMRO2) and changes in mitochondrial O2 tension () were calculated. 100%Wmax was approximate to 33% lower in the older group. Exercise increased MAP and CO in both groups (P < 0.05 vs. rest), but at each intensity MAP was higher and CO lower in the older group (P < 0.05). MCA Vmean, and cerebral vascular conductance index (MCA Vmean/MAP) were lower in the older group at each exercise intensity (P < 0.05). In contrast, young and older individuals exhibited similar increases in CMRO2 (by approximate to 30 mol (100 g1) min1), and decreases in OCI (by approximate to 1.5) and (by approximate to 10 mmHg) during exercise at 75%Wmax. Thus, despite the older group having reduced cerebral perfusion and maximal exercise capacity, cerebral oxygenation and uptake of lactate and glucose are similar during exercise in young and older individuals.