My symptoms are related to barometric pressure. The days it's low I feel much better, the higher it is, the worse I feel. If I have to go upstairs to the third floor in the attic, I can feel pressure in my head immediately. There is also more heat in the attic during the summer so maybe it's the heat but perhaps there is less air in your basement affecting you? Just throwing it out there.
I recently had to fly to Colorado for my son's wedding and it was brutal. The elevation did a number on my head and I struggled to get through.