Background: Weight loss is common in Parkinson's disease (PD). However, little is known when it starts, how it changes as PD progresses, and whether there is a differential loss of lean or fat mass.Methods: In the Health ABC study (n=3075, age range 70-79), body composition was assessed by dual-energy X-ray absorptiometry from baseline (year 1) to year 10. For each PD patient at each year, we calculated the difference between body composition measures and their expected values had they not developed PD, and then realigned the time scale in reference to the year of PD diagnosis. Using both inverse variance-weighted fixed-effects linear model and linear mixed model with cross random effects, we examined the trend of change for each body composition measure before and after PD diagnosis. Results: During an average of 7.8 years of follow-up, a total of 81 PD patients were identified. PD patients were more likely to be men (59.3% vs. 48.2%) and white (74.1% vs. 57.9%) than non-PD participants. Compared with their expected weight, PD cases began to lose weight and fat mass several years before PD diagnosis( p-values for trend were 0.003 and <0.001 for total body mass and fat mass, respectively). Conclusions: In this longitudinal analysis, we found persistent weight loss, predominantly in fat mass, in PD patients starting a few years before diagnosis.
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