Cataracts as a potential non-motor marker for Parkinson's disease: An observational study based on UK biobank data

Although Parkinson’s disease (PD) is primarily classified as a movement disorder, it is frequently accompanied by a spectrum of non-motor symptoms, some of which can precede the onset of motor symptoms by over a decade. Early recognition of these non-motor symptoms provides an opportunity for earlier diagnosis and intervention. Recent research has explored the potential association between cataracts and PD, though findings have been inconsistent. Therefore, the aim of this study was to analyze and validate whether cataracts could serve as a potential non-motor marker for PD. This study utilized data from the UK Biobank, a large prospective cohort study of over 500,000 participants, to investigate the relationship between cataracts and PD using Cox proportional hazards models. A nested case-control analysis of the data from matched case-controllers was performed based on newly diagnosed cataracts during the follow-up period. The primary analyses included 293,261 participants aged 55–70 years. In the univariate Cox regression analysis, cataracts were associated with an increased risk of PD (hazard ratio [HR] = 1.57, 95 % confidence interval [CI]: 1.332–1.850, P = 6e-08). This association remained statistically significant across all three multivariate models, which were adjusted for different sets of covariates. Subgroup analyses demonstrated that cataracts were linked to a higher risk of PD across nearly all subgroups. Furthermore, sensitivity analyses excluding participants diagnosed with PD within 1 or 5 years of baseline yielded consistent results. In the case-control study, 53,626 participants with cataracts diagnosed during the follow-up period were 1:1 matched with healthy controls according to sex and age. This analysis similarly found that cataracts were associated with increased PD risk (odds ratio [OR] = 1.389, 95 % CI: 1.240–1.555, P = 1e-08). However, the Mendelian randomization analysis did not support a causal relationship between cataracts and PD (OR = 1.098, 95 % CI: 0.856–1.407, P = 0.462), indicating that although an association exists between cataracts and PD, it may not reflect a direct causal pathway. In summary, this study identified a significant association between cataracts and an increased risk of developing PD, suggesting that cataracts might serve as a potential non-motor marker of PD. Further research is warranted to elucidate the underlying mechanisms linking cataracts to PD.