BackgroundDementia following spine fusions is not described in the literature. Also, the impact of new onset dementia on long-term health care utilization is not described. The aim of our study was to define the incidence of new onset dementia and its long-term health care utilization in elderly patients. Materials and methodsMarketScan database were queried using the ICD-9/10 and CPT 4th edition, from 2001 to 2019. We included patients≥55 of age who underwent spine fusions with at least 5years follow-up. Outcomes were new onset dementia (>6months after the procedure) length of stay (LOS), discharge disposition, hospital readmissions, outpatient services, and medication refills. ResultsOf 45,129 patients who underwent spine fusions, 1283 patients (2.84%) were diagnosed to have new onset dementia. There was no difference in the reoperation rates among the dementia and non-dementia cohort at 1-, 2- and 5-years following the index procedure. Patients in the dementia cohort incurred higher number of hospital readmissions up to 5-years after the index procedure. In terms of combined index procedure and post-discharge utilization payments, significant differences were noted among the dementia vs. non-dementia cohorts at 5-years ($126,628 vs. $77,098), following the index procedure. ConclusionElderly age, higher comorbidities, Medicare insurance, multilevel lumbosacral fusions were identified as risk markers for developing dementia following spine fusions. Dementia resulted in significantly higher health care utilization with no increased rate of reoperations for up to 5-years following the index procedure.