ABSTRACTS

Objective: In humans, male births exceed female births. This ratio is conventionally expressed as 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 of America (USA), 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 the period 2003–2013 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 out for the entire group and for White and Black/African American births.

Results: This study analysed 45 138 496 live births (23 102 106 males, 22 036 390 females, M/F: 0.51180). Overall, M/F was the lowest in election years, rising, then falling 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 the elections. Black births may have been unaffected due to chronic stress caused by socio-economic dampening of M/F trends.