Late-onset schizophrenia should be distinct subtype
MedWire News: Late-onset schizophrenia (LOS), occurring over the age of 40 years, should be considered a distinct subtype of schizophrenia, say researchers.
They found sufficient clinical difference between early-onset schizophrenia (EOS) and LOS that could not be explained by Deficit Syndrome.
However, the team notes that distinctions between the two groups were based on clinical evaluations and not on psychobiological differences.
“Thus, we are not able to determine if there are underlying biological distinctions between EOS and LOS,” they report in the journal Acta Psychiatrica Scandinavica.
Dilip Jeste, from the University of California in San Diego, USA, and colleagues carried out assessments of psychopathology, neurocognition, and functioning in 854 schizophrenia outpatients older than 40 years, of whom 110 had LOS (≥40 years) and 744 EOS (<40 years), as well as 359 mentally healthy individuals.
The results showed that both LOS and EOS patients had greater levels of psychopathology, cognitive impairment, and functional disability than healthy controls.
The EOS and LOS patient groups were similar with regard to education, severity of depressive, negative, and deficit symptoms, crystallized knowledge, and auditory working memory.
However, the LOS group included more women and married individuals, and they had less severe positive symptoms and general psychopathology, with average scores on the Positive and Negative Syndrome Scale (PANSS) of 14.0 versus 15.5 for EOS patients and 27.9 versus 30.2, respectively.
LOS patients also performed better than EOS patients with regard to processing speed (Digital symbol score=5.3 vs 4.7), abstraction (Wisconsin Card Sorting Test score=45.0 vs 39.3), verbal memory (California verbal learning test score=10.7 vs 9.2), and everyday functioning, as measured on the UCSD performance-based skills assessment (score=72.0 vs 67.6), the Social Skills Performance Assessment (score=28.4 vs 26.4), and the Quality of Life Wellbeing Scale (score=0.6 vs 0.5). They were also on lower doses of antipsychotic medication.
After adjusting for severity of negative or deficit symptoms and duration of illness as possible counter explanations for the differences between EOS and LOS patients, all the differences except for positive symptom severity, cognitive flexibility, and verbal memory remained significant.
“Our results suggest that LOS and EOS show sufficient overlap to warrant consideration as a single disorder… yet there are important differences with regard to gender, symptom severity, executive impairment, health-related quality of life, everyday functioning, and prognostic indicators that should warrant specification of LOS as a subtype,” say Jeste et al.
“Doing so has heuristic value in facilitating further study of LOS; the insights gained from such research may also open new avenues for prevention and treatment that could be applied to persons with EOS and even to those at high risk for schizophrenia.”
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By Lucy Piper