Experts have long thought that Parkinson disease processes begin about 5 or 6 years before the classic motor symptoms (slowness, tremor, rigidity) show up.
Now it is looking like the disease begins its work at least 20 years before motor symptoms appear. The first symptoms may be things that are "annoying" but would not necessarily alarming, such as constipation and some sleep disorders. There may also be some problems with the sense of smell and depression before motor symptoms are present.
Hopefully, researchers will develop a way to figure out how to detect Parkinson disease early, which could also lead them to discover a way to slow the disease process.
Source: Savica R, Rocca WA, Ahlskong JE. "When Does Parkinson Disease Start?" Arch. Neurology. 2010; 67(7); 798-801.

This is scary! How would you know it is onset of Parkinson’s or menopause or or or????
I want to know why my younger sister`s hand is trembling.She is age of only 43 but her moving action was very slow and i said you looks like a tortise.This year she become more weakness and thin.I want to be look more healthy with good complexion but she had stress and sleepless night.You had written all about the sign of Parkinson disease are met on her body.Could she suffer the Parkinson or what disease you think.This is the weakness from the neuro system of brain.First i am scare of storke or paralys.I want to know more about what treatment is better for her.Some doctors said B12 deficiency can cause paralyse and parkinson.
san san – have her thyroid checked!! Also tests for autoimmune disease. I had the same problem only to discover Grave’s Disease was causing my trembling, weightloss and weakness.
Thanks to research in recent years, scientists have found links between celiac disease, gluten sensitivity and leaky gut. With any of these 3 issues undetected and serious B12 deficiency can build over years and have a permanently destructive effect on the nervous ssystem—and cause the tremor, muscular problems etc. Also, since thyroid disease can be caused or exacerbated by consumption of gluten—and some symptoms of hypothyroidism are sleep disorders and constipation—doctors need to connect the dots. For some people it may be easy to prevent degenerative nerve disorders later in life by hhaving up to date thyroid tests and tests ofr gluten issues and leaky gut syndrome.
One other thing—aspartame is a neurotoxin that can cause symptoms like those of Parkinsons. Bot of my aunt and mother cosumed copious quantities of aspartame sweetened soda for decades. Now both of them have bad shaking and tremors. No other relatives in my family ever had parkinson’s—and none of them ever consumed products with aspartame.
It’s something to be aware of.