The symptoms of PD are noticable when there is already loss of 60-80% of the dopamine cells.

If your apnea coincided with the other symptoms, it argues for it being a symptom rather than the cause. Hypoxia may accelerate the process however.

Sleep breathing disorders in patients with idiopathic Parkinson's disease
Our results suggest that sleep breathing disorders, predominantly obstructive, seem to be common in PD and those events correlate with the severity of the disease.

Ronhutton, isn't hypoxia associated with BBB damage?