If you spend more than five hours a day at a workstation, your computer may affect your physical and your mental health. And a new study is sending a troubling message down the information superhighway. Japanese rearchers studied 25,000 workers for over three years. They found that it only takes five hours a day at a computer to make you feel tired and weary, to lose interest in work and even to have trouble falling asleep. One possible reason for all that.. all that work at a workstation creates too much mental stress. The study also found physical problems like eye strain start to build long before five hours., and grow worse over time. So if your job ties you to a computer all day, what do you do? Researchers suggest therapy, exercises, and taking breaks. And for eye strain, you can change your focus from looking at something close to looking far away.