Risk for cancer in a cohort of patients hospitalized for schizophrenia in Denmark, 1969-1993

We investigated the cancer risk of patients hospitalized for schizophrenia in a nationwide cohort study. All 22 766 adults admitted for schizophrenia, ICD-8 295, in Denmark between 1969 and 1993 were followed up for cancer through 1995. The incidence of site-specific cancers was compared with national incidence rates, adjusted for sex, age and calendar time. The risk for cancer was increased for both men and women during the first year of follow-up. When the first year of follow-up was excluded, the risk for all tobacco-associated cancers and for prostate and rectal cancers was reduced for male patients with schizophrenia. The standardized incidence ratio (SIR) of lung cancer was marginally reduced (SIR, 0.86; 95% CI: 0.65, 1.02) for male patients with schizophrenia; this was due, however, to a reduction in risk for older patients. An increased risk for breast cancer found for female patients with schizophrenia (SIR, 1.20; 95% CI: 1.05, 1.38) should be interpreted with caution, given the high proportion of nulliparous women with schizophrenia in Denmark. The data might support reduced risks for prostate and rectal cancer among male patients with schizophrenia, whereas a changing smoking pattern might explain the reduced risk for tobacco-related cancers.