Trajectory of change in body mass index in Parkinson's disease

Gastrointestinal (GI) symptoms are some of the most common non-motor symptoms in Parkinson's. Weight is a nutritional metric and can be affected by dysfunction of the gastrointestinal (GI) tract. This study aims to explore the change in trajectory of body mass index (BMI) in individuals with Parkinson's over the course of the disease including the prodromal and post-diagnostic periods.

This was a retrospective longitudinal study of data from participants from the PRIME Parkinson UK cross-sectional study. Participants were included if they had had one or more weights and height recorded in the primary care electronic health record.

287 patients were initially included but only 234 could be included in the analysis of BMI trajectory. Using a piecewise linear mixed model, we determined that there was a 'change point' in BMI trajectory. This occurred on average 3.73 years after diagnosis, when the mean BMI was 26.4 kg/m². Prior to this change point, the estimated mean rate of change in BMI was -0.09 kg/m² (95 % credible interval -0.20,0.00 kg/m²) per year. However, after the change point, we observed a more accelerated decline in BMI, with an estimated mean rate of change of -0.34 kg/m² (95 % credible interval -0.70,-0.07 kg/m²) per year.

There was a modest weight loss trajectory in the pre-diagnostic period consistent with clinically stable weight. However, after several years, post-diagnosis BMI loss became more marked. In clinical practice interventions could be targeted at this time point to optimize and maintain nutritional intake.