(1) To examine the relationship between OSA severity and Small Vessel Disease (SVD) in patients with ischemic stroke/TIA. (1a) To assess whether these associations may be present only in select brain regions with specific types of SVD. (2) To examine the relationship between OSA, SVD and cognition.

Cerebral small vessel disease (SVD) is the most common cause of vascular dementia. On MRI SVD manifests as White Matter Hyperintensities (WMH), lacunes, enlarged perivascular spaces and microbleeds. Obstructive Sleep Apnea (OSA) is the most common sleep disorder and meta-analytic data supports a relationship between OSA and SVD. The purpose of this study is to examine relationships between: (1) OSA severity and SVD (2) OSA severity, SVD and cognition.

Patients with ischemic stroke/TIA were prospectively recruited across three independent cohort studies. Years of education, vascular risk factors, stroke severity and Montreal Cognitive Assessment scores were collected. All patients completed MRI and either an in-laboratory polysomnography (PSG) or Home Sleep Apnea Test (HSAT). OSA severity was quantified using the Apnea Hypopnea Index (AHI). The burden of small vessel disease was quantified using validated visual rating scales. Ordinal logistic regression models examined relationships between OSA and SVD, while controlling for covariates.

In 237 patients increasing AHI was associated with a greater burden of periventricular WMH (pWMH) OR=1.02 (CI:1.01 to 1.04, p=0.02), deep microbleeds OR=1.03 (CI:1.01 to 1.05, p=0.002) and lobar microbleeds OR=1.02 (CI:1.01 to 1.04, p=0.03). Finally, in an ordinal logistic regression model, lower cognitive scores were related to cerebral microbleeds OR=1.09 (CI:1.01 to 1.18, p = 0.03) while controlling for covariates.

OSA severity is associated with greater periventricular WMH and cerebral microbleeds. Cerebral microbleeds are predictive of lower cognitive scores. The relationship between OSA and both lobar and deep microbleeds suggests potential associations with nocturnal hypertension and cerebral amyloid clearance.