I would think it would be hard to differentiate the effects of the adrenaline rush caused by skydiving from the altitude effects especially for first timers who are going to have a larger adrenaline rush than experienced jumpers.
However, I work in a lab that studies the effects of chronic intermittent hypoxia in rats and compares that to sustained hypoxia. The point of the model is to compare chronic intermittent hypoxia to disease states like obstructive sleep apnea whereas sustained hypoxia is more like the adaptation to high altitude living conditions.
The early results suggest that the body is able to adapt to sustained hypoxia at tolerable levels but not to repeated bouts of toxic levels of hypoxia. How does this relate to jumping? I'm not sure if it can be compared but the mild hypoxic conditions during a jump below 15k could be similar to a hypoxic event. The severity seems less than that seen in a bout of sleep apnea and the event frequency is less b/c of how often you can jump and how many you do in a day, week, or year but there may be reasonable comparison with understood limitations.
