Hello- I took omreprazole every day for 15 years. It was heaven - until my original gastro called me to tell me that I needed to get off of it immediately as you are only supposed to take it for 15 DAYS! It causes osteoporosis - CAUSES - no discussion. Also, the absence of the burning sensation can make many people think that they have no problem and they can have the beginning/growth of cancerous tissues without any symptoms.
As for going to sleep-I never had any problems when I took it. It worked so well that I would forget to take it and often take it before bed or in the middle of the night. It works too good - while it is causing irreversible bone damage.
I take mine at night, usually about 30 minutes before going to sleep, because that's when my reflux is the worst. I sleep just fine. I'm not sure that there's any difference in the affect on the body if you take it at night vs the morning.
My gastro advised me to do this because reflux was waking me up in the middle of the night. It works well for me.