A herniated disk, sometimes (incorrectly) called a slipped disk, is a common cause of severe back pain and sciatica. A disk in the lumbar area becomes herniated when it ruptures or thins out, and degenerates to the point that the gel within the disk (the nucleus pulposus) pushes outward.
The ceiling fan's downrod must be long enough for the fan's blades to clear the ceiling. A fan with a 12-inch downrod works for a vaulted ceiling with a one-quarter-to one-third-inch pitch. An 18-inch downrod is sufficient for a pitch that is five-twelfths to one-half inch.
In a prior house we installed a ceiling fan and 4 recessed cans in the cathedral ceiling of our MBR. The flat portion of the of the ceiling was 10' by 12' with the fan in the middle and the cans in the 4 corners about 2' from the corners. The fan was hanging down on a 36 downrod. There was a lot of strobing when the fan was on. I think that the effect would be minimized if you maximize the distance between the end of the fan blade and the light.