Late and very-late first-contact schizophrenia and the risk of dementia-a nationwide register based study

Objective To examine whether late and very‐late first‐contact schizophrenia carry a risk for later development of dementia. Methods By linkage of the psychiatric and the somatic nation‐wide registers of all out‐ and in‐patients with hospital contact in Denmark, we identified all patients with first ever contact during the period from January 1994 to December 2001 with one of the index main diagnoses: late (age ≥40) and very‐late first‐contact (age ≥60) schizophrenia. First contact osteoarthritis patients as well as data on the general population were used as controls. The first diagnosis of dementia for each individual at discharge or at out‐patient contact was established. The probability of getting a dementia diagnosis is estimated using Poisson regression models with dementia as the outcome of interest. Results Twelve thousand six hundred and sixteen and 7,712 individuals were included in the late and very‐late sample, respectively. Follow‐up time was between 3.00 and 4.58 years. The rate ratio (RR) of developing dementia in late and very‐late first‐contact schizophrenia compared to osteoarthritis patients were 3.47 (95%CI: 2.19–5.50) and 3.15 (95%CI: 1.93–5.14), respectively. Compared to the general population the RR were 2.36 (95%CI: 1.54–3.62) and 2.21 (95%CI: 1.39–3.50), respectively. Conclusion schizophrenic patients with late‐ and very‐late first‐contact with the psychiatric hospital system are at two to three times higher risk of subsequently getting a diagnosis of dementia compared to patients with osteoarthritis and compared to the general population. Copyright © 2008 John Wiley & Sons, Ltd.