Objectives: Behavioural and psychological symptoms of dementia (BPSD) are common in patients with dementia. In the elderly population, comorbidities frequently coexist with dementia and mortality in dementia is high. The aim of this study was to investigate the impact of BPSD on mortality in severe dementia. Methods: This study of 11,448 individuals was based on linked information from the Swedish BPSD registry, the National Patient Register and the Cause of Death register. BPSD was assessed with the Neuropsychiatric Inventory (NPI). Cox proportional hazards regressions were performed for survival analysis. To study different degrees of BPSD, data was categorized into groups: no (NPI, 0 points), mild (NPI, 1-3 points on !1 item), moderate (NPI, 4-8 points on !1 item) and severe (NPI, 9-12 points on !1 item) BPSD based on the highest score on any of the BPSD assessed (NPI items). Results: The presence of moderate or severe BPSD was associated with a stepwise increased risk of mortality (hazard ratio (HR), 1.31; 95% confidence interval (CI), 1.08-1.60 and HR 1.74; 95% CI 1.44-2.12, respectively) compared with individuals with no BPSD. In addition, there was an association between total NPI score and mortality (HR 1.01; 95% CI 1.007-1.010). The results remained significant after multivariable adjustment for age, sex, dementia diagnosis, medication, previous myocardial infarction, hip fracture and stroke. Conclusions: The results show a stepwise increase in mortality risk with increased BPSD, highlighting the importance of adequate management of BPSD to reduce mortality in dementia.

Background: Register diagnoses, both hospital-based and from open clinic care, are often used in research studies in Sweden. The validity of such diagnoses has been debated and a validation assessment can improve the diagnostic accuracy for use in research studies. Objective: The aim of this study was to investigate the quality of register-derived dementia diagnoses in the Malmö Diet and Cancer population study (MDCS) and to validate these diagnoses using systematic criteria. Methods: MDCS is a population-based prospective study comprising 30,446 participants. Register diagnoses of dementia for the MDCS population were derived from the Swedish National Patient Register (NPR) and validated through re-evaluation of available medical records by physicians. Results: In the MDCS cohort, 2,206 participants were diagnosed with dementia according to the NPR during a mean follow-up of 18.1 years. The general dementia diagnosis was valid in 96% of the cases, but 40% of the specific dementia diagnoses were changed during the process of reevaluation. The diagnostic validity varied between 25.2% and 82.9% for the different diagnoses. The results from the validity assessment per diagnostic category revealed that the validity of the NPR diagnoses was higher for the more specific diagnoses and lower for unspecified dementia. The major diagnostic shift during the re-evaluation was from unspecified dementia to more specific diagnoses. Conclusion: Validation of dementia diagnoses using medical records results in more precise diagnoses. Dementia diagnoses derived from registers should be validated in order to study associations between influential factors and different dementia diagnoses.