Being Born in Winter–Spring and at Around the Time of an Influenza Pandemic Are Risk Factors for the Development of Schizophrenia: The Apna Study in Navarre, Spain

Abstract

Background: We analyzed the relationship between the prevalence of schizophrenia and the season of birth and gestation during a period of an influenza pandemic. Methods: Cross-sectional analysis of a prospective population-based cohort of 470,942 adults. We fitted multivariant logistic regression models to determine whether the season of birth and birth in an influenza-pandemic year (1957, 1968, 1977) was associated with schizophrenia. Results: 2077 subjects had been diagnosed with schizophrenia. Logistic regression identified a significantly greater prevalence of schizophrenia in men than in women (OR = 1.516, CI 95% = 1.388–1.665); in those born in the winter or spring than in those born in the summer or autumn (OR = 1.112, CI 95% = 1.020–1.212); and in those born in a period of an influenza pandemic (OR = 1.335, CI 95% = 1.199–1.486). The increase in risk was also significant when each influenza pandemic year was analyzed separately. However, neither month of birth nor season of birth, when each of the four were studied individually, were associated with a statistically significant increase in that risk. Conclusions: The winter–spring period and the influenza pandemics are independent risk factors for developing schizophrenia. This study contradicts many previous studies and thus revitalizes a locked debate in understanding the neurodevelopmental hypothesis of this disorder.

Anthropometry in antipsychotic-naïve first-episode psychosis patients: An exploratory approach to the role of environmental early life events in two independent samples

“…Season of birth was described as winter birth being born between December 21 st and the 21 st of March, spring was described as birth between March 21 st and June 21 st , summer as between June 21 st and September 21 st and autumn as between September 21 st and December 21 st . In supplementary material we describe results with a different temporal description of season of birth (Alvarez-Mon et al, 2021) based on the meteorological season dates: summer (June, July, August), autumn (September, October, November), winter (December, January, February), and spring (March, April, and May). Our approach towards astronomical birth season was due to an increased prevalence in seasonal flu from late December to late March according to the Spanish National Flu Surveillance system (https://vgripe.isciii.es/inicio.do) around the years when patients/controls were born, which fits better in our MIA approach due to an increased prevalence of concomitant viral infections.…”

Schizophrenia and Hospital Admissions for Cardiovascular Events in a Large Population: The APNA Study

“…It started in 2004 in the autonomous community of Navarre (northern Spain). Details on the cohort design are available elsewhere [14][15][16][17][18][19].…”

Infections and mental diseases: from tuberculosis to COVID-19

“…Schizofrenię stwierdzono u 2077 osób, 1,5 raza częściej u mężczyzn niż u kobiet. Analiza przeprowadzona metodą regresji logistycznej wykazała istotnie większe ryzyko zachorowania na schizofrenię osób urodzonych w latach pandemii, zarówno łącznie, jak i w poszczególnych latach [26].…”