Association of Incidentally Discovered Covert Cerebrovascular Disease Identified Using Natural Language Processing and Future Dementia

BACKGROUND: Covert cerebrovascular disease (CCD) has been shown to be associated with dementia in population-based studies with magnetic resonance imaging (MRI) screening, but dementia risk associated with incidentally discovered CCD is not known. METHODS AND RESULTS: Individuals aged ≥50 years enrolled in the Kaiser Permanente Southern California health system re-ceiving head computed tomography (CT) or MRI for nonstroke indications from 2009 to 2019, without prior ischemic stroke/ transient ischemic attack, dementia/Alzheimer disease, or visit reason/scan indication suggestive of cognitive decline or stroke were included. Natural language processing identified incidentally discovered covert brain infarction (id-CBI) and white matter disease (id-WMD) on the neuroimage report; white matter disease was characterized as mild, moderate, severe, or undetermined. We estimated risk of dementia associated with id-CBI and id-WMD. Among 241 050 qualified individuals, natural language processing identified 69 931 (29.0%) with id-WMD and 11 328 (4.7%) with id-CBI. Dementia incidence rates (per 1000 person-years) were 23.5 (95% CI, 22.9– 24.0) for patients with id-WMD, 29.4 (95% CI, 27.9– 31.0) with id-CBI, and 6.0 (95% CI, 5.8– 6.2) without id-CCD. The association of id-WMD with future dementia was stronger in younger (aged <70 years) versus older (aged ≥70 years) patients and for CT-versus MRI-discovered lesions. For patients with versus without id-WMD on CT, the adjusted HR was 2.87 (95% CI, 2.58– 3.19) for older and 1.87 (95% CI, 1.79–1.95) for younger patients. For patients with versus without id-WMD on MRI, the adjusted HR for dementia risk was 2.28 (95% CI, 1.99– 2.62) for older and 1.48 (95% CI, 1.32–1.66) for younger patients. The adjusted HR for id-CBI was 2.02 (95% CI, 1.70– 2.41) for older and 1.22 (95% CI, 1.15–1.30) for younger patients for either modality. Dementia risk was strongly correlated with id-WMD severity; adjusted HRs compared with patients who were negative for id-WMD by MRI ranged from 1.41 (95% CI, 1.25–1.60) for those with mild disease on MRI to 4.11 (95% CI, 3.58– 4.72) for those with severe disease on CT. CONCLUSIONS: Incidentally discovered CCD is common and associated with a high risk of dementia, representing an oppor-tunity for prevention. The association is strengthened when discovered at younger age, by increasing id-WMD severity, and when id-WMD is detected by CT scan rather than MRI.