Apolipoprotein E polymorphism is associated with age of onset in schizophrenia

Abstract

The aims of the study were to investigate the relationship between Apolipoprotein E (APOE) polymorphism, risk of schizophrenia, treatment response to conventional anti-psychotics, and age of onset in schizophrenia. The sample comprised 94 Finnish patients with a DSM-IV diagnosis of schizophrenia. Forty-three of the patients were good responders to conventional anti-psychotics and 51 were classified as non-responders. The control group consisted of 98 healthy blood donors. The APOE allele frequencies (ε2, ε3, and ε4) were 4.8, 72.3, and 22.9% in patients and 7.1, 75.0, and 17.9 in controls. None of the differences between groups were statistically significant. No association between treatment response and APOE genotype was found. Patients with APOE ε4/ε4 genotype had a markedly lower age of onset compared with rest of the sample (p = 0.0015), which remained significant when controlling for gender (p = 0.02). There was an increasing linear trend between the number of ε3 alleles (0, 1, or 2) and age of onset in schizophrenia (p = 0.08). An inverse trend was found between the number of ε4 alleles and age of onset (p = 0.07). No relationship between APOE polymorphism and risk for schizophrenia was found. APOE ε4/ε4 genotype may be associated with early onset schizophrenia. APOE ε3 allele may function protectively in later onset in this disease.