Does meditation in general if practiced for long periods of time by anyone, even by an atheist for health reasons, expands his awareness to satan or demons?
Power Meditation will start to open the Soul and Psychic centers over time, if done consistently. So yes. No one would be able to continue being an Atheist when they started to actually experience their own Soul and the presence of Satan and the Gods.
This can take a long time though. Years, in some cases. It's all individual and depends on the level your Soul is at when you first start meditating.