The primary cause of hands falling asleep in the evening and while sleeping is a condition known as carpal tunnel syndrome, according to WebMD. People commonly feel tingling and numbness that travels from the hands to the shoulder.
People with carpal tunnel syndrome experience numbness in the hands primarily in the evening and while sleeping because the hand is in a relaxed position, explains WebMD. Some patients experience burning and an itching numbness with this condition. Severe cases of carpal tunnel syndrome produce loss of feeling in the fingers, an inability to use the thumb to pinch, slower nerve impulses and a loss of coordination and strength.