The change in hair color is due to varying levels of Melanin. When the quantity of Melanin decreases in a person, it causes the hair to turn lighter. There are several factors that could lead to lighter hair color such as aging, Vitiligo, Malnutrition, Werner Syndrome, Pernicious Anemia etc. I would suggest you to get yourself a proper checkup and tests so that the exact cause can be found out.
