I have used computers since two decades ago, almost daily, for hours. When I was younger, there was no effect on my health, but after 30's the body doesn't recover as quickly as before, and some discomfort appeared gradually until becoming pain, mainly in my hands and right elbow. It's a condition known as Repetitive Stress Injury (RSI). I was diagnosed of abuse syndrome, and currently I never can use the computer's keyboard without pain. Fortunately the pain doesn't appear at the piano, but I think that the disorder affects my ability to control my touch and to articulate trills.
So, you guys and girls accustomed to use the computer for hours, learn the lesson, and take it easy: Place the keyboard comfortably, key in softly, don´t keep the hand on the mouse when you aren't using it, also in order to avoid undue pressure on the nerves don´t keep the forearms on the table, and above all take pauses often. Go to doctor if some pain is persistent.
My piano teacher says, "if pain appears during playing, something wrong is being done". So, don't neglect to play keeping the shoulders, arms, hands and fingers as relaxed as possible all the time.