What you've described seems to make sense too. I would think the lack of oxygen and the extra exertion to breathe would be physically exhausting.
I also read an interesting study on children who were burdened with parasites. They were behind in their school studies and had troubles with comprehension. After parasites were addressed, they improved in school overall. It made me start thinking about this and how this is overlooked. I'm wondering if those children who are called lazy or slow might be victims of parasites, sinus problems (possibly mold related), and environmental toxins.