Ventilatory responses to exercise and CO2 after menopause in healthy women: Effects of age and fitness

Hypercapnia-induced vasodilation in the cerebral circulation is reduced in older adults with sleep-disordered breathing

The prevalence of sleep-disordered breathing (SDB) is higher in older adults compared with younger individuals. The increased propensity for ventilatory control instability in older adults may contribute to the increased prevalence of central apneas. Reductions in the cerebral vascular response to CO₂ may exacerbate ventilatory overshoots and undershoots during sleep. Thus, we hypothesized that hypercapnia-induced cerebral vasodilation (HCVD) will be reduced in older compared with younger adults. In 11 older and 10 younger adults with SDB, blood flow velocity in the middle cerebral artery (MCAV) was measured using Doppler transcranial ultrasonography during multiple steady-state hyperoxic hypercapnic breathing trials while awake, interspersed with room air breathing. Changes in ventilation, MCAV, and mean arterial pressure (MAP) via finger plethysmography during the trials were compared with baseline eupneic values. For each hyperoxic hypercapnic trial, the change (Δ) in MCAV for a corresponding change in end-tidal CO₂ and the HCVD or the change in cerebral vascular conductance (MCAV divided by MAP) for a corresponding change in end-tidal CO₂ was determined. The hypercapnic ventilatory response was similar between the age groups, as was ΔMCAV/Δ[Formula: see text]. However, compared with young, older adults had a significantly smaller HCVD (1.3 ± 0.7 vs. 2.1 ± 0.6 units/mmHg, P = 0.004). Multivariable analyses demonstrated that age and nadir oxygen saturation during nocturnal polysomnography were significant predictors of HCVD. Thus, our data indicate that older age and SDB-related hypoxia are associated with diminished HCVD. We hypothesize that this impairment in vascular function may contribute to breathing instability during sleep in these individuals.NEW & NOTEWORTHY This study demonstrates, for the first time, in individuals with sleep-disordered breathing (SDB) that aging is associated with decreased hypercapnia-induced cerebral vasodilation (HCVD). In addition to advanced age, the magnitude of nocturnal oxygen desaturation due to SDB is an equal independent predictor of HCVD.

Influence of ACTN3 R577X polymorphism on ventilatory thresholds related to endurance performance

The purpose of this study was to verify the association between ACTN3 polymorphism and physiological parameters related to endurance performance. A total of 150 healthy male volunteers performed a maximal incremental running test to determine the speeds corresponding to ventilatory threshold (VT) and respiratory compensation point (RCP). Participants were genotyped and divided into terciles based on the analysed variables. Genotype frequencies were compared through χ(2) test between lower and higher terciles, with the lowest or highest values of each analysed variable. ACTN3 XX genotype was over-represented in higher tercile for VT and RCP. Odds ratio also showed significantly higher chances of XX individuals to be in higher tercile compared to RR (7.3) and RR + RX (3.5) for VT and compared to RR genotype (8.1) and RR + RX (3.4) for RCP. Thus, XX individuals could attain the VT and RCP at higher speeds, suggesting that they are able to sustain higher running speeds in lower exercise intensity domains. It could result in higher lipid acids oxidation, saving muscle glycogen and delaying the fatigue during prolonged exercises, which could be the advantage mechanism of this genotype to endurance performance.