This seems like an odd question given that only a small percentage of people actually get Parkinson’s disease. Nevertheless, the question has always perplexed me.
Here’s my rationale. The main neurons responsible for the motor
symptoms of Parkinson’s disease are dopamine-containing cells that project from the substantia nigra pars compacta to the striatum. In the striatum, each nigrostriatal dopamine neuron branches into a dizzying array of tiny appendages that make hundreds of thousands of synapses.1, 2 And these neurons do not merely send the occasional message. They are pacemakers, constantly firing at a slow, steady rate, hour after hour, year after year. Can you imagine how much energy it takes to constantly transport cargo to hundreds of thousands of branches? How many mitochondria these cells need to produce adequate energy? Recycle vesicles? Make new neurotransmitter? Get rid of old proteins and organelles? You’d think the nigrostriatal dopamine neurons would simply wear out in all of our brains.