There are common cognitive and brain abnormalities in schizophrenia and healthy aging which may cumulate in schizophrenia aging. However, the course of executive deficits in late-life schizophrenia is still controversial as it remains unclear whether schizophrenia patients show accelerated aging. The use of specific models of executive functions might help to shed new lights on this issue. The aim of this study was then to determine how each of the four specific executive functions (shifting, updating, inhibition and access to long-term memory) is affected by aging in schizophrenia compared to healthy aging. 20 younger (age 18-34), 17 middle-aged (age 35-49) and 25 older (age 59-76) schizophrenia patients and 62 healthy comparison participants matched for gender, age and education performed a neurocognitive battery evaluating the four specific executive functions. Schizophrenia patients performed worse than comparison participants on shifting, updating and access, whereas inhibition appeared preserved. Age affected the four functions with increased degradation of shifting and access in schizophrenia patients, whereas updating and inhibition showed a normal decline with age. These results suggest a vulnerability of prefrontal and cingulate cortexes in schizophrenia aging. Moreover, as age affected the specific executive functions differently, remediation programs should be adapted to older patients. Models of specific executive functions are useful for understanding the complexity of cognition in schizophrenia and its course during later life so that healthcare can be adapted accordingly.
Background
Executive deficits are a core characteristic of schizophrenia. Yet, the origin of these impairments remains unclear as they may be caused by processing slowing. This issue is of particular interest for aging insofar as cognitive aging is also associated with a decline in executive functioning and a slowing of processing speed. As schizophrenia patients’ life expectancy increases, a better understanding of the origin of older patients’ cognitive deficits becomes essential so that healthcare can be adapted to suit them. This study aims to determine whether processing speed mediates how schizophrenia affects executive functions and whether these relationships are moderated by age.
Methods
Sixty-two schizophrenia patients (27 women) and 62 healthy comparison subjects matched for age (range: 18–76 years), gender and education performed neurocognitive tests to evaluate their executive functions (shifting, updating, inhibition and access) and processing speed.
Results
Processing speed mediated the effect of schizophrenia on the four specific executive functions, and age moderated this mediation for shifting, updating and access, but in different ways. Age moderated the effect of processing speed on shifting, the direct effect of schizophrenia on access, and both the effect of processing speed and the direct effect of schizophrenia on updating.
Conclusions
This research highlights the need to evaluate processing speed routinely during therapeutic follow-up, as it is easy and simple to assess and appears to be at the heart of the cognitive deficits in schizophrenia. Finally, processing speed abilities yield information about the evolution of cognition with aging in schizophrenia.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.