AbstractBackgroundStudies suggest dementia patients have higher rates of non‐traumatic intracranial hemorrhage (nt‐ICH) compared to cognitively‐unimpaired peers. Recent studies also suggest increased risk of nt‐ICH, following infection with Covid‐19 in the general population. However, the risk of nt‐ICH following Covid‐19 infection in cognitively‐impaired individuals is currently unknown.MethodUsing US electronic health records ICD codes, we matched Alzheimer’s disease (AD), dementia, and mild cognitive impairment (MCI) cases with a history of Covid‐19 to similarly cognitively impaired controls without Covid‐19 history and examined incidence of nt‐ICH over six‐months following infection. Cases and controls were propensity score matched on age, sex, race, ethnicity, time since cognitive‐diagnosis, anticoagulant use, antiplatelet use, and 37 comorbidities. Analyses focused on the first year of the pandemic in 2020, prior to availability of at‐home tests and vaccines, to reduce misclassification bias. Individuals with prior history of nt‐ICH, traumatic ICH, or stroke were excluded to focus on incident nt‐ICH. Cox proportional hazard models compared risk between those with and without Covid‐19.ResultOur sample included 2,287 AD cases with Covid‐19 matched to 6,861 AD controls; 5,726 dementia cases matched to 17,178 dementia controls; and 807 MCI cases matched to 2,419 MCI controls. The incidence of nt‐ICH following Covid‐19, among AD cases, was 12.53/1,000 person‐years (95% CI: 7.66‐19.36) vs. 4.16/1,000 person‐years (95% CI: 2.51‐6.50) in AD patients without Covid‐19; HR = 3.1 (95% CI: 1.7, 5.8), p = 0.0004. Similarly in dementia patients, Covid‐19 increased the risk by 3.0 times (95% CI: 1.8, 4.7), p<0.0001. The incidence in dementia Covid‐19 cases was 8.48/1,000 person‐years (95% CI: 5.91, 11.80) vs. 2.97/1,000 person‐years (95% CI: 2.07, 4.13) in dementia patients without a history of Covid‐19 over the study period. The incidence in MCI patients with a history of Covid‐19 was 5.03/1,000 person‐years (95% CI: 1.37, 12.87), vs. 1.56/1,000 person‐years (95% CI: 0.32, 4.57) in MCI controls, but risk was not significantly different; HR = 3.4 (95% CI: 0.8, 15.0), p = 0.11.ConclusionAlthough nt‐ICH was rare among cognitively impaired patients following Covid‐19 infection in 2020, the risk over 6‐months in AD and dementia cases was approximately 3 times higher than controls without a history of Covid‐19.