Age spots, or liver spots, are very common in people over 50. Despite their name, though, and their tendency to show up later in life, they are not caused by aging. They occur due to long-term sun exposure.
To prevent aging spots on the hands, limit the time that you spend in the sun and use a hand lotion with SPF 30 each day. If you already have them, then use an OTC fading cream with 2% hydroquinone.