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 >or=40) and very-late first-contact (age >or=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.