Just happened across these two papers by the same author. Presented as hypotheses, they are nonetheless worth thinking about-

1- Physical activity, eccentric contractions of plantar flexors, and neurogenesis: therapeutic potential of flat shoes in psychiatric and neurological disorders. - Flensmark J.
"...The use of heeled shoes results in less eccentric contractions with decreased neurogenesis. People in the Western World wore heeled shoes from the beginning of the 17th century, and, because of the decreased neurogenesis, the prevalence of diseases such as depression, epilepsia, Alzheimer's disease, Parkinson's disease, schizophrenia, diabetes, and myopia increased. Use of flat shoes produces stronger eccentric contractions and increases neurogenesis...."
and
2- Is there an association between the use of heeled footwear and schizophrenia? - Flensmark J.
"...During walking synchronised stimuli from mechanoreceptors in the lower extremities increase activity in cerebello-thalamo-cortico-cerebellar loops through their action on NMDA-receptors. Using heeled shoes leads to weaker stimulation of the loops. Reduced cortical activity changes dopaminergic function which involves the basal ganglia-thalamo-cortical-nigro-basal ganglia loops. Bicycle riding reduces depression in schizophrenia due to stronger stimulation by improved lengthening contractions of the triceps surae muscles...."

I dismissed this at first, but now I'm not so sure. The lowest rates for PD are in warm countries with fewer shoes. I find that I go barefoot around the house far more than I used to. I come on faster if I stretch my legs. Any thoughts?
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I don't wear my shoes in the house. I put them on when I go outside. I'm home a lot. Most of the time. I don't take medication but have gotten worse the past year.

I tend to think PD was lying in my genes and something came along to awaken it. Like a bad sleeping beauty.