Objective: In humans, male births exceed female births. This ratio is conventionally expressed to M/F and is influenced by a large number of factors, including stress. This study was carried out in order to ascertain whether the known seasonal variation in M/F in the United States (peaking in June) is affected by the quadrennial elections (November), and whether any such influences vary by race.
Methods: Births by gender and by race for 2003-13 were obtained from the website of the Centers for Disease Control and Prevention for the four available races: White, Black/African American, Asian/Pacific Islander and American Indian/Alaska Native. Election years were 2004, 2008 and 2012. Seasonality tests were carried for the entire group and for White and Black/African American births.
Results: This study analysed 45138496 live births (23102106 males, 22036390 females, M/F 0.51180). Overall, M/F was lowest in the election years rising, then falling again to the next election year (p=ns). This pattern was present for White and Asian/Pacific Islander births but not for Black/African American or American Indian/Alaskan Native births. Overall and for White births, only election year plus 3 (year just before election) showed seasonal variation (p < 0.01).
Conclusion: Seasonality may have been disturbed/reduced in most years due to elections. Black births may have been unaffected due to chronic stress caused by socio-economic dampening of M/F trends.
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