ObjectiveTo investigate the relationship between enlarged perivascular spaces (EPVS) and measures of Alzheimer disease (AD), small vessel disease (SVD), cognition, vascular risk factors, and neuroinflammation, we tested associations between EPVS and different relevant neuroimaging, biochemical, and cognitive variables in 778 study participants.MethodsFour hundred ninety-nine cognitively unimpaired (CU) individuals, 240 patients with mild cognitive impairment, and 39 patients with AD from the Swedish Biomarkers for Identifying Neurodegenerative Disorders Early and Reliably (BioFINDER) study were included. EPVS with diameter >1 mm in centrum semiovale (CSO), basal ganglia (BG), and hippocampus (HP); hippocampal volume; white matter lesions (WML); and other SVD markers were determined from MRI. CSF levels of β-amyloid42 (Aβ42), phosphorylated tau, total tau, and neuroinflammatory markers; amyloid accumulation determined with [18F]-flutemetamol PET; and vascular risk factors and results from cognitive tests were determined and collected.ResultsEPVS in CSO, BG, and HP were associated with WML volume and Fazekas score in individuals without dementia. No associations were found between EPVS and CSF Aβ42, total tau and phosphorylated tau, neuroinflammatory markers, vascular risk factors, and cognitive tests. EPVS in HP were associated with hippocampal atrophy. In a matched group of individuals with AD and CU, EPVS in HP were associated with AD diagnosis.ConclusionsEPVS are related to SVD, also in early disease stages, but the lack of correlation with cognition suggests that their importance is limited. Our data do not support a role for EPVS in early AD pathogenesis.