Male fertility, unlike female fertility, doesn’t decline to the point of complete infertility. There are no limits, either in age or number, to the amount of sperm produced in a lifetime. Despite being forever fertile, male fertility does decline with age. The exact age depends on the man, but there are some universal changes in male sperm to consider. 

Fertility Time ClockThe Young and Vibrant Sperm
Prior to 35, male sperm is young and vibrant. Testosterone levels are normal and everything is in perfect working order. After 35, things start to change and while fertility is not an issue for all men in the later years of life, offspring health is a huge consideration. 

The Male/Female Synergistic Effect
If the female in the relationship is under 35 and the male is older than 35, mom protects the offspring against increased risk of Down syndrome. However, once mom ages beyond 35, her eggs are older as well and older eggs increase the risk of Down syndrome thus the two aging bodies work together to increase the overall risk of Down syndrome dramatically. 

Other Age/Sperm Related Medical Conditions
Studies have shown a dramatic increase in autism, schizophrenia, dwarfism and other rare medical conditions with advanced paternal age. For instance, a man over the age of 40 is six times more likely to have a child with autism, no matter the maternal age. Schizophrenia risk increases three times when paternal age advances beyond 50. Again, maternal age does not play a factor. 

Symptoms of Age-Related Reduced Male Fertility
The two most common symptoms of age-related reduced male fertility are low sperm count and reduced semen volume. Fewer sperm and less fluid transferred from male to female decreases the overall chance of pregnancy, but this doesn’t mean late in life conception is impossible. Men have fathered children well into their 70s, but with late in life conception comes increased risk of serious medical conditions.