At Human Reproduction, Yash S. Khandwala and colleagues have an article titled "The Age of Fathers in the USA is Rising: an Analysi of 168,867,480 Births from 1972 to 2015." The abstract:
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.
Why mention this study here?
In addition to delayed time to conception, the effects of advanced paternal age on offspring health can be significant. Numerous reports have found increased risk of autism, psychiatric illness, neurologic disease such as neurofibromatosis, pediatric cancer and chromosomal abnormalities in children born to older fathers (Bray et al., 2006; Croen... et al., 2007; Puleo et al., 2012; Snajderova et al., 2012; Gratten et al., 2016).