Association of handgrip strength asymmetry with prodromal and incident Parkinson's disease: A prospective cohort study

Background Asymmetry symptoms are well recognized in Parkinson's disease (PD). However, whether handgrip strength (HGS) asymmetry can prospectively predict incident PD remains unknown. Objectives To prospectively examine the association between HGS asymmetry and subsequent risk of incident PD . Methods Included were 497,100 participants without PD at baseline from the UK Biobank. HGS asymmetry index was calculated by dividing the absolute inter-hand difference in HGS by the average HGS of the two hands. The primary outcome was incident PD identified through hospital admissions, death registries, and self-reported data. As secondary outcome, prodromal PD was defined as the presence of ≥3 out of 8 prodromal PD features assessed through self-reported data, hospital admission records and primary care data. The associations were evaluated using Cox regression models. Several lag analyses were conducted to examine how many years in advance could HGS asymmetry predict incident PD. Results During a median follow-up of over 13 years, 2868 participants developed PD. HGS asymmetry (highest vs. lowest quartile) was associated with higher risk of developing PD (HR = 1.23; 95% CI: 1.10, 1.37) ( P- trend < 0.001). Lag analysis suggested that HGS asymmetry could even predict incident PD in 8 years. Significant association between HGS asymmetry and prodromal PD risk was also observed. The significant associations between HGS asymmetry and PD risk persisted when further excluding those with low HGS or prodromal PD. Conclusions Higher HGS asymmetry was associated with a higher risk of incident PD, suggesting the potential of HGS asymmetry as an early indicator for PD.