Late-Onset Schizophrenia: Relationship to Awareness of Abnormal Involuntary Movements and Tobacco Addiction

Abstract

Although schizophrenia usually emerges at mid to late-adolescence, it has been estimated that almost 20% of schizophrenic patients develop their first symptoms in mid to late life (late-onset schizophrenia). The biological characteristics that distinguish patients with early onset from those with late-onset schizophrenia have not been well delineated. A subgroup of neuroleptic-treated schizophrenic patients develops tardive dyskinesia (TD) and the majority of these patients are unaware of their movements. To investigate whether early and late-onset schizophrenic patients with TD could be differentiated on the basis of awareness of involuntary movements, we compared the prevalence of awareness of these abnormal movements in patients with early (N = 40) and late-onset (N = 15) schizophrenia. We found a significantly higher prevalence of awareness of involuntary movements in patients with late-onset schizophrenia as compared to those with an earlier age of onset (86.6% vs. 25.0%, p < .0001). In a second study, we investigated whether early and late-onset schizophrenia could be differentiated on the basis of dopamine functions in the mesolimbic system. Since tobacco addiction is mediated via limbic dopaminergic functions, we investigated the prevalence of tobacco addiction in patients with early (N = 51) and late-onset (N = 13) schizophrenia. We found a significantly lower prevalence of tobacco addiction in patients with late-onset schizophrenia as compared to those with an earlier age of onset (15.4% vs. 54.9%; X2 = 6.49; p < .01). Our findings support the notion that distinct pathophysiological mechanisms underlie the development of early and late-onset schizophrenia.