Attila Sipos

Paternal age and schizophrenia: a population based cohort study

Abstract Objective To investigate the association of paternal age at conception with the risk of offspring developing schizophrenia. Design A population based cohort study. Setting Sweden. Subjects 754 330 people born in Sweden between 1973 and 1980 and still alive and resident in Sweden at age 16 years. Main outcome measures Hospital admission with schizophrenia or non-schizophrenic, non-affective psychosis. Results After adjustment for birth related exposures, socioeconomic factors, family history of psychosis, and early parental death the overall hazard ratio for each 10 year increase in paternal age was 1.47 (95% confidence interval 1.23 to 1.76) for schizophrenia and 1.12 (0.98 to 1.29) for non-schizophrenic non-affective psychosis. This association between paternal age and schizophrenia was present in those with no family history of the disorder (hazard ratio for each 10 year increase in paternal age 1.60, 1.32 to 1.92), but not in those with a family history (0.91, 0.44 to 1.89) (P = 0.04 for interaction). Conclusions Advancing paternal age is an important independent risk factor for schizophrenia. The stronger association between paternal age and schizophrenia in people without a family history provides further evidence that accumulation of de novo mutations in paternal sperm contributes to the overall risk of schizophrenia.

Association between psychotic disorder and urban place of birth is not mediated by obstetric complications or childhood socio-economic position: a cohort study

BACKGROUND Although urban place of birth has been identified as a risk factor for schizophrenia, the extent to which this association is mediated by socially patterned risk factors such as obstetric complications and childhood socio-economic position is unclear. The diagnostic specificity of the association within the clinical psychotic syndromes is also unclear. METHOD A population cohort of 696025 males and females, born in Sweden between 1973 and 1980 and with linked birth and socio-economic data was followed up from age 16 for up to 9.8 years. Hospitalized cases of schizophrenia and other non-affective psychosis were identified from the Swedish Inpatient Discharge Register. We examined associations of these disorders with a three-level measure of urbanicity of birthplace before and after controlling for measures of foetal nutrition, obstetric complications and level of maternal education. RESULTS Urban compared to rural birthplace was associated both with increased risk of adult onset schizophrenia (hazard ratio 1.34, CI 0.91-1.96) and other non-affective psychoses (hazard ratio 1.63, CI 1.18-2.26). None of these associations was greatly affected by adjustment for obstetric complications or maternal educational level. In the group of other non-affective psychoses urban-rural differences in disease risk were strongest among those born in the winter months. CONCLUSION Urbanization of birthplace is associated with increased risk of non-affective psychosis but this is not confined to narrowly defined cases. The magnitude of the association in Sweden is lower than that reported in other studies. Causal factors underlying this association appear to operate independently of risks associated with obstetric complications and parental educational status.

Is the season of birth association with psychosis due to seasonal variations in foetal growth or other related exposures? A cohort study

Objective:  To investigate the association between season of birth and psychosis, and to assess whether any association is caused by seasonal fluctuations in foetal growth or other related exposures.