Being Born during a Flu Pandemic as Risk Factors for Development of Schizophrenia

Abstract Background Schizophrenia is a neurodevelopmental disorder of complex etiopathogenesis involving genetic and environmental factors. Mother’s exposure to infectious agents during pregnancy has been, implicated in the pathogenesis of schizophrenia. Studies in experimental models support that flu virus can cause embryonic neurodevelopment damage such as that described for embryos that later develop schizophrenia, but epidemiological studies of the association between schizophrenia and gestation in times of a documented flu pandemic) are contradictory. Methods The study is a cross-sectional study within the APNA Study (Navarre primary health care prospective cohort) that included 470942 people over 18 years old in Navarre (Spain). Date of birth, sex, and schizophrenia diagnoses made by psychiatrist on the basis of ICD-10 were extracted. People were classified according if their birth dates occurred within or around periods of flu pandemics in the second half of the 20th century: 1957, 1968 and 1977. The dates for these groups were from January of the year of the pandemic until December of the subsequent year. Logistic regression of adjusted by sex, age, and month of birth was performed. Because the cohort only includes people over 18 years of age, data for patients born during the influenza A subtype H1N1 outbreak of 2009 were not available. Results Males have a higher prevalence of schizophrenia than females (OR = 1.516, 95% CI: 1.388-1.655), Adjusting by gender, month of birth and age, subjects born during (or the year after) years of flu pandemic relative to subjects born in non-pandemic years (OR = 1.335, 95% CI = 1.199-1.486). The latter relationship held for each pandemic studied in isolation of the others, with ORs of 1.476 (95% CI: 1.244-1.750) for the 1957-59 pandemic, 1.261 (95% CI: 1.060-1.493) for the 1968-70 pandemic and 1.280 (95% CI: 1,072- 1,528) for the 1977-78 pandemic. Conclusions Been born during a flu pandemic may increase the risk of developing schizophrenia. Key messages Exposure to the influenza virus during gestation may increase the risk of schizophrenia. Flu Vaccination in pregnant women may reduce the risk of schizophrenia in their children.