We achieve peak performance at 25. After that we continuously reduce
The hair becomes thinner as the hormone and nutrient balance change. The first gray hair can appear, depending on the disposition
Brain maturation processes are complete. The brain loses a bit of it's weight
First signs of aging. The skin becomes drier, the structure more uneven. Gradually the skin loses its originally radiant appearance and appears dull
Strength, speed, endurance and mobility decrease. That is why most competitive athletes end their careers after 30
Testosterone levels decrease in men. They reached the maximum at the age of 20
Women are at a high hormone level. Their libido is at its peak
The bone density has reached its maximum. From now on, more bone mass is lost than built up
Men's sperm quality seems to deteriorate after the age of 35. The proportion of sperm carrying an X chromosome also seems to increase, meaning older dads are more likely to have daughters
To investigate, Bronte Stone at Reproductive Technology Laboratories in Los Angeles and his colleagues analysed sperm samples from 5081 men aged between 16 and 72. They found a deterioration in sperm quality and quantity after age 35. The study also found a decrease in the ratio of Y to X-bearing sperm once men hit 55, though it is not clear why
Men over age 40 are twice as likely as men under age 25-29 to have a child with autism, but only if the mother is under age 25
A review in 2005 found a U-shaped relationship between paternal age and low intelligence. The highest IQ was found at paternal ages of 25-29; fathers younger than 25 and older than 29 tended to have children with lower IQs
Men and women both transmit an increasing number of new mutations to their children as they age, according to a study published in Nature