Author(s): ANANDARAJAH, J., CURTIN, E., WESTON, M., BUYS, P., HEANEY, R., TEALE, J., WILLIAMSON, W., EGAÑA, M., GILDEA, N., Institution: TRINITY COLLEGE DUBLIN, Country: IRELAND, Abstract-ID: 2506

INTRODUCTION:
Dynamic cerebral autoregulation (dCA), the capacity of the cerebrovasculature to buffer transient fluctuations in arterial blood pressure, is critical for maintaining cerebral perfusion. Impaired dCA has been reported in individuals with type 2 diabetes, a population at elevated risk of cognitive decline. However, whether similar cerebrovascular dysfunction is evident in pre-diabetes (PD), an early stage of glycaemic dysregulation, remains unexplored. Aerobic fitness is proposed to modulate cerebrovascular function, though its influence may be population-dependent. Therefore, this pilot study aimed to determine whether (1) dCA is impaired in individuals with PD and (2) dCA is associated with aerobic fitness.
METHODS:
7 individuals with PD (5 females; 67土6.20 years) and 7 normoglycemic controls (CON) (4 females; 59土3.60 years) volunteered to take part in the study, completing two visits. On visit one, participants performed a ramp incremental cycling test to exhaustion followed by a verification bout to determine maximal oxygen uptake (V̇O₂max). On visit two, dCA was assessed using a single sit to stand manoeuvre (2 mins seated, 3 mins standing). Middle cerebral artery velocity (MCAv) and mean arterial pressure (MAP) were measured via Transcranial Doppler Ultrasonography and finger plethysmography. Baseline MCAv and MAP were taken as the last 60 seconds of seated rest. dCA was quantified as the percentage fall in MCAv relative to the percentage fall in MAP within the first 20 secs of standing (Δ%MCAv/Δ%MAP). Initial orthostatic hypotension (IOH) was defined as a fall in SBP ≥40 mmHg or DBP ≥20 mmHg within 15 seconds of standing. CVCi was calculated by MCAv/MAP. Independent-sample t-tests were used to compare dCA metrics, while Pearson correlations examined associations between V̇O₂max and dCA.
RESULTS:
Baseline MCAv and MAP did not differ between CON and PD (P=0.27 and P=0.48). Furthermore, reductions in MCAv and MAP upon standing did not differ between groups (P=0.80 and P=0.70), nor did dCA index (P=0.27). IOH was not observed in either group. Moderate, but not significant, associations were observed between VO₂max and both CVCi (r = – 0.52, P = 0.23) and dCA (r = 0.69 and p to=0.09); likely reflecting the limited sample size.
CONCLUSION:
This pilot study revealed dCA responses during a single sit-to-stand manoeuvre are preserved in individuals with pre-diabetes, with no evidence of initial orthostatic hypotension. These preliminary findings suggest that early glycemic dysregulation may not yet compromise dynamic cerebrovascular control. Furthermore, significant correlations were not observed between measures of dCA and aerobic fitness. However, given the limited sample size, larger adequately powered studies are required to confirm these observations and to determine whether subtle impairments emerge with disease progression.