AbstractObjectivesLoss of weight is associated with cognitive decline as well as several adverse outcomes in dementia. The aim of this study was to assess whether weight loss is associated with mortality and hospitalization in dementia subtypes.MethodsA cohort of 11,607 patients with dementia in Alzheimer's disease (AD), vascular dementia (VD), or dementia with Lewy bodies (DLB) was assembled from a large dementia care health records database in Southeast London. A natural language processing algorithm was developed to established whether loss of weight was recorded around the time of dementia diagnosis. Cox proportional hazard models were applied to examine the associations of reported weight loss with mortality and emergency hospitalization.ResultsWeight loss around the time of dementia was recorded in 25.5% of the whole sample and was most common in patients with DLB. A weight loss‐related increased risk for mortality was detected after adjustment for confounders (Hazard ratio (HR):1.07; 95% confidence interval (CI):1.02–1.15) and in patients with AD (HR: 1.11; 95% CI: 1.04–1.20), but not in DLB and VD. Weight loss was associated with a significantly increased emergency hospitalization risk (HR: 1.14; 95% CI: 1.08–1.20) and in all three subtypes.ConclusionsWhile there were associations with increased hospitalization risk for all three subtype diagnoses, weight loss was only associated with increased mortality in AD. Weight loss should be considered as an accompanying symptom in dementia and interventions should be considered to ameliorate risk of adverse outcomes.