It has been well established that maternal age is a significant risk factor for the development of trisomy 21, more commonly referred to as Down Syndrome. Indeed, there are a number of tests that are offered during the prenatal period to assist in the early detection of this genetic mutation. However, links between paternal age and disease have not been as vigorously evaluated.
Recent research published by the journal Nature suggests that there is a positive correlation between a father's age and the development of mental conditions such as autism and schizophrenia. Though this does not necessarily imply a causative relationship, it is of great interest to researchers as it appears that fathers pass down a greater amount of genetic mutations than mothers. The paper rightly points out that genetic mutations are vital for natural evolution; however, as stated by Kong et al., the "estimated exponential effect of paternal mutations doubling every 16.5 years is striking." It is thus believed that the chance of deleterious mutations, that is, those that result in a loss of particular functions, increases proportionally with the age of fathers at conception.
Autism, one of the conditions thought to be influenced by a father's age, is a very peculiar condition and its underlying etiology remains largely unknown. What is known however, is that the number of cases of autism has been increasing drastically over the last decade and that according to Kong et al., the father's age (in Iceland) at conception moved from 27.9 to 33 years between 1980 and 2011. Accordingly, the authors state that "Demographic change of this kind and magnitude is not unique to Iceland, and it raises the question of whether the reported increase in ASD (Autism Spectrum Disorder) diagnosis lately is at least partially due to an increase in the average age of fathers at conception."