Abstract: Objective To compare the characteristics of tremor and improvement after acute levodopa challenge test in young onset Parkinson's disease (YOPD) and late onset Parkinson's disease (LOPD) with a cross-sectional study. Methods From Match to September, 2017, 70 Parkinson's disease inpatients with rest or postural tremor in at least one extremity were included, in which 23 patients were in YOPD group, and other 47 in LOPD group according to their ages of onset. They finished acute levodopa challenge test and were analyzed for dominant tremor frequency, amplitude and rhythm under resting state, posturing and holding 1000 grams state, respectively. Results YOPD group was younger (t=-2.423, P<0.01) with lower Hoehn-Yahr stage (χ²=-4.604, P<0.05), and needed less equivalent dose of levodopa at early stage (first five years) (t=-2.119, P<0.05). There was a bigger ratio of patients with rest tremor in frequency of four to six Hz in YOPD group than in LOPD group (χ²=3.896, P<0.05). Rigidity and bradykinesia scores of LOPD group positively correlated with the course of disease (r=0.34, P<0.05), while it was not found in YOPD group.Conclusion Tremor expresses most in the classical way in YOPD patients, and tremor analysis could help to diagnose young adults. Both YOPD and LOPD patients get well in acute levodopa challenge test, while YOPD patients need less equivalent dose of levodopa at early stage.

Key words: young onset Parkinson's disease, late onset Parkinson's disease, tremor, acute levodopa challenge test, tremor analysis