The age of fathers in the USA is rising: an analysis of 168 867 480 births from 1972 to 2015

Study question: How has the mean paternal age in the USA changed over the past 4 decades?

Summary answer: The age at which men are fathering children in the USA has been increasing over time, although it varies by race, geographic region and paternal education level.

What is known already: While the rise in mean maternal age and its implications for fertility, birth outcomes and public health have been well documented, little is known about paternal characteristics of births within the USA.

Study design, size, duration: A retrospective data analysis of paternal age and reporting patterns for 168 867 480 live births within the USA since 1972 was conducted.

Participants/materials, setting, methods: All live births within the USA collected through the National Vital Statistics System (NVSS) of the Centers for Disease Control and Prevention (CDC) were evaluated. Inverse probability weighting (IPW) was used to reduce bias due to missing paternal records.

Main results and the role of chance: Mean paternal age has increased over the past 44 years from 27.4 to 30.9 years. College education and Northeastern birth states were associated with higher paternal age. Racial/ethnic differences were also identified, whereby Asian fathers were the oldest and Black fathers were the youngest. The parental age difference (paternal age minus maternal age) has decreased over the past 44 years. Births to Black and Native American mothers were most often lacking paternal data, implying low paternal reporting. Paternal reporting was higher for older and more educated women.

Limitations, reasons for caution: Although we utilized IPW to reduce the impact of paternal reporting bias, our estimates may still be influenced by the missing data in the NVSS.

Wider implications of the findings: Paternal age is rising within the USA among all regions, races and education levels. Given the implications for offspring health and demographic patterns, further research on this trend is warranted.

Study funding/competing interest(s): No funding was received for this study and there are no competing interests.

Trial registration number: N/A.