As men age, they lose the Y chromosome in more and more of their cells, a common process affecting probably all men[1][2]. About 40 percent of men in their 60s and up to 57 percent of men in their 90s lose their Y chromosome[1]. This loss is associated with serious health problems including heart disease, cancer, neurodegeneration and Alzheimer's disease[2]. Scientists have found that the loss of the Y chromosome significantly disrupts the immune system and can increase the risk of cancer and acute infections[2]. Research in mouse models has shown that Y-deficient cells lead to impaired heart function and heart failure[1]. Y chromosome loss is one-third genetic and is increased by environmental factors such as smoking and exposure to carcinogens[1]. Scientists believe that this loss may be responsible for about half of the difference in life expectancy between the sexes[2].