You may think of a cat nap as a short snooze, but cats are actually supersleepers, often slumbering for 12 to 18 hours a day. That’s healthy for them, but for humans, sleeping more than an hour while the sun shines can be a sign of developing liver problems, according to a study in BMC Gastroenterology. It found that compared with folks who don’t nap, those who slept for 60 minutes or more in the …