Abstract COVID has disproportionately impact nursing home (NH) residents – estimates are that more than 35% of deaths have occurred among NH residents. In order to prevent COVID spread among vulnerable elderly, NHs across the U.S. have instituted a number of interventions, including restricting access to NHs by non-employees, isolating patients within NHs, reducing group activities within NHs, and transferring patients out of NHs to other facilities. These measures have the potential to exacerbate social isolation, quality of care, and quality of life among NH patients with Alzheimer’s disease and Related Dementias (AD/ADRD). There is an extensive literature on social support within NHs and other institutional settings. In contrast, there is relatively little in the way of research in the opposite extreme – isolation – despite the fact that patient isolation in the context of infection control is common, especially among NH patients, where infections with resistant organisms are more common than in the community setting. Furthermore, other aspects of isolation – social isolation, emotional/psychological isolation, and physical isolation – present barriers to the effective care and safety of patients with AD/ADRD and without AD/ADRD in NHs. Patients with AD/ADRD are exceptionally at risk for adverse outcomes due to isolation in nursing homes. They have greater dependency on familiar individuals and settings, directed activities, require greater assistance, and are at risk for confusion and agitation when these are absent. Patients with AD/ADRD have greater challenges with communicating needs. In order to assess the national impact of the pandemic on patient care and outcomes among NH residents with and without AD/ADRD, we propose in this administrative supplement to develop and implement measures to assess patient isolation and relate these cross sectionally and longitudinally to patient outcomes among AD/ADRD patients in California NHs from 2011 to 2018. Specifically, the aims of this administrative supplement are to: Develop proxy measures for assessing baseline patient isolation – social, emotional, and physical Determine whether baseline patient isolation is predictive of patient quality of care, utilization of care, and outcomes Determine whether baseline patient isolation is related to end-of-life care preferences as reported in the California MDS Section S, where POLST responses are recorded. Taken together, these findings for a patient isolation construct using existing data can be employed with national MDS data to examine the degree to which patient isolation changed among AD/ADRD patients and whether it was a determinant of adverse patient outcomes during the COVID Pandemic.