Impaired cerebrovascular reactivity (CVR) in patients with obstructive sleep apnea syndrome (OSAS) increases the risk of ischemic stroke. CVR also decreases with age in normal individuals. However, it is unclear whether OSAS affects CVR differently in young and old patients. The aim of this study was to compare CVR in old and young patients with OSAS via transcranial Doppler (TCD) measurements of changes in cerebral blood flow velocity in the middle cerebral artery (MCAmv) during breath holding and hyperventilation.
A total of 20 old patients (≥65 y) and 40 young patients (<65 y) with similar distributions of sex and OSAS severity were recruited for this study. The breath-holding index (BHI) and the hyperventilation index (HVI) were calculated to measure CVR.
No differences were found in MCAmv at baseline, apnea or hyperventilation between the two groups with different OSAS severities. However, reduced BHI (P < 0.01) and HVI (P < 0.01) were found in the young group with increasing severity of OSAS. Notably, the decline in BHI and HVI associated with OSAS severity was steeper in young patients than in old patients (P < 0.01).
These findings suggest that CVR in young patients is more impacted by OSAS severity than that in old patients, suggesting the existence of age-related cerebrovascular susceptibility to OSAS.

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