Changes in Body Composition Before and After Parkinson's Disease Diagnosis

Background: Weight loss is common in Parkinson's disease (PD). However, little is known about when it starts, how PD changes as it progresses, and whether there is a differential loss of lean or fat mass. The objective of this study was to examine how body composition changes before and after PD diagnosis. Methods: In the Health, Aging, and Body Composition study (n = 3075; age range, 70–79 years), body composition was assessed using dual-energy x-ray absorptiometry on an annual or biennial basis from year 1 to year 10. For each PD case each year, we calculated the difference between their actual body composition measures and expected values had they not developed PD. Using linear mixed models with crossed random effects, we further examined the trend of change in body composition measures before and after PD diagnosis. Results: A total of 80 PD cases were identified in this cohort. Compared with their expected values, PD cases began to lose total and fat mass about 6–7 years before diagnosis, although the differences were not statistically significant until 3–5 years after diagnosis. The loss was substantial and persistent, with statistically significant trends of loss for total body mass (P = 0.008), fat mass (P = 0.001), and percentage fat (P < 0.001). In comparison, lean mass was stable throughout the follow-up (P = 0.16). Overall, 96% of the body mass loss in PD cases was from the loss of fat mass. Conclusions: In this longitudinal analysis with objective measures of body composition, we found persistent weight loss in PD cases, predominantly in fat mass, starting a few years before diagnosis.