Are Late- and Very-Late-Onset Schizophrenia Precursors of Dementia?

Background/Objective: To examine whether patients with late-onset schizophrenia (LOS) and very-late-onset schizophrenia-like psychosis (VLOS) are at a higher risk of developing dementia than patients with early-onset schizophrenia (EOS). Methods: A random sample of incident cases of patients with schizophrenia with an age of onset after age 40 (LOS) and age 60 (VLOS) was selected from a psychiatric case register covering all psychiatric services within the city of The Hague, The Netherlands, between 1997 and 2012. Schizophrenia diagnosis and age of onset were audited by systematic review of all case notes up to 2019. Patients who were initially misclassified as LOS/VLOS in the registry but, after this audit, had an age of onset before age 40, were classified as EOS. The risk of developing dementia was compared between the groups using a logistic regression model with correction for age, gender, and stroke as possible confounders. Results: Our study groups consisted of 74 patients with EOS, 81 with LOS, and 25 with VLOS. Dementia was present in 10 patients at follow-up, 7 out of 106 (6.6%) patients in the combined LOS and VLOS groups, and 3 out of 74 (4.1%) patients in the EOS group. However, after correction for confounders, logistic regression showed no statistically significant higher change in the development of dementia in LOS nor VLOS patients compared to EOS patients, nor with age of onset as a continuous variable. Conclusions: Patients with LOS and VLOS are not at a higher risk of developing dementia compared to patients with EOS. These results do not support the hypothesis that LOS and especially VLOS, are precursors of dementia.