Yes of course you can close your eyes with wearing contacts lenses. The eyes of people have to blink millions of times each day, so it is ok and a must to close your eyes when you are wearing contacts. However, you should not wear your contacts when you are sleeping whether at night or at noon. Some people do not take off their contacts when going to bad because they think it inconvenient and takes time to take the contacts off and then put them back on again. This is a very bad and harmful habit. If you are wearing congtacts when you are asleep, your eyes are closed, and will not blink, therefore, the secretion and circulation of tears decrease, leading to the tangible objects in the eyes' conjunctival sac easily depositing on the contacts, which worsens the oxygen deficit of cornea. If you usually wear contacts when you sleep, kompensatorisch will make new vessels grow around the cornea contributing cornea edema and epithele cells damaged, which is fatal to your eyes. Therefore, you should not wear your contacts when you are sleeping.
You can certainly close your eyes with wearing contact lenses. But you cannot sleep with them for too long time, for they will cause irritation to your eyes and damage your eyesight. If you sleep for 10-15 minutes with them, it is OK. But after that, your contact lenses will be very dry, sticky and out of the right place. Besides, you may have difficulty in readjust them. If you accidentally fall asleep with your contact lenses still in your eyes, you can put your lenses in the lens solution to make them moist again. Whether contact lenses are harmful to your eyes depends on yourself because the chance of contact lenses-related eye disease is small if you follow the advice of your doctor and use the contact lenses correctly.
Well, it seems that you are worried about your eye health. From what I know, it would be unwise for you to do that because that is just like sleeping with contact lenses in, which would generate some damages to your eyes, and by closing your eyes for much too long, your eyes start to be stifled. Thus, you'd better not try that and make good use of your eyes. Wear less of contact lenses would be a healthy way.