Correlation between age and MMSE in schizophrenia

Abstract

Background: The Mini-Mental State Examination (MMSE) is widely used in schizophrenia, although normative data are lacking in this population. This review and meta-regression analysis studies the effect of aging on MMSE scores in schizophrenic patients.

Methods: We entered the search terms schizophrenia and MMSE in PubMed and PsychInfo. Bibliographies of pertinent articles were also examined. We included every study presenting the MMSE scores in schizophrenic patients along with a corresponding mean age. We conducted our analyses using simple linear regression weighted for the inverse of within-trial variance of the age variable, thus conferring more importance to studies with narrower age groups.

Results: We identified 56 articles (n = 5,588) published between 1990 and 2012. The MMSE scores of schizophrenic patients decline by approximately 1 point for every four years (y = 34.939-0.247x, 95% Confidence Interval (CI) [-0.304, -0.189], R 2 = 0,545), which is five times the rate in the general population. Institutionalized patients account for a large proportion of this decline (y = 37.603-0.308x, 95% CI [-0.349, -0.267], R 2 = 0.622) whereas community-dwelling patients are relatively stable throughout aging (y = 27.591-0.026x, 95% CI [-0.074, 0.023], R 2 = 0.037).

Conclusions: Subgroup analyses show different trajectories between institutionalized and outpatients with schizophrenia. The deterioration observed in institutionalized patients may have to do with greater illness severity, heavier medication load, vascular risk factors, and lack of stimulation in institutional settings. Studies documenting the role of these variables would be useful. Cognitive screening tools that assess executive functions would be interesting to study in schizophrenics, as they may reveal more subtle age-related cognitive changes not measured by the MMSE.

Keywords: Mini-Mental State Examination; aging; cognition (neuro-cognitive functions); review; schizophrenia.