Citations

Background: Neurological diseases share overlapping systemic and molecular features, but the specificity and interpretation of cross-disease metabolomic signatures remain uncertain. Methods: We analyzed summary-level Nightingale NMR metabolomic and genetic data from 274,241 UK Biobank participants across eight neurological endpoints. The disease rankings used here were derived from baseline plasma metabolites predicting future incident disease rather than from contemporaneous diagnostic case–control contrasts. Results: Among 57 priority metabolites with genome-wide significant instruments (2472 SNPs; mean F = 162.4), nine ranked in the top 30 for at least seven of the eight endpoints, defining a shared pre-diagnostic neurological signature confirmed as non-random cross-endpoint convergence by permutation testing (p < 0.0001). Because we did not perform a quantitative non-neurological disease control analysis, this signature should not be interpreted as neurologically specific and may partly reflect systemic morbidity, renal function, body composition, or frailty-related physiology. Forward Mendelian randomization across 45 metabolite–disease pairs found no Bonferroni-significant causal effects; three nominal protective associations are consistent with the number of false-positive findings expected under multiple testing and require replication. Conclusions: These results support a shared systemic, pre-diagnostic metabolic signature across the neurological disease spectrum, while the null MR findings and specificity limitations favor interpretation as a biomarker or prodromal downstream signal rather than a proven causal mechanism. External prospective validation is essential.

Abstract Background Parkinson's disease (PD) represents a growing global health challenge, with prevalence doubling from 2.5 million cases in 1990 to 6.1 million in 2016, and projections suggesting it will exceed 12 million by 2040. This exponential growth has been termed the "Parkinson's pandemic." China and the United States, which together account for nearly half of the global PD population, have developed markedly different approaches to end-of-life (EOL) care, shaped by their distinct healthcare systems and cultural contexts. Understanding these differences is crucial for developing effective global strategies. This systematic review and meta-analysis comprehensively compares advanced-stage PD care between these two nations to quantify disparities and inform evidence-based policy interventions. Methods We conducted a rigorous systematic review following PRISMA 2020 guidelines, searching six databases (PubMed, Embase, Scopus, Web of Science, CNKI, Wanfang) from January 2015 to October 2025. The timeframe was selected to capture contemporary care patterns following major healthcare reforms in both countries (Affordable Care Act implementation in the US; Healthy China 2030 initiative). Inclusion criteria encompassed peer-reviewed studies reporting on advanced PD (Hoehn-Yahr stage ≥ 3) with outcome measures including survival, quality of life (QoL), palliative care access, caregiver burden, rehabilitation utilization, or healthcare costs. The sample size threshold (n ≥ 100) balanced statistical power with inclusivity. Two independent reviewers screened 3,847 records with excellent agreement (Cohen's κ = 0.82–0.89). Quality assessment employed the Newcastle-Ottawa Scale (NOS ≥ 8 indicating high quality) and ROBINS-I for observational studies, with GRADE criteria determining evidence certainty. Meta-analyses utilized random-effects models with comprehensive heterogeneity assessment (I² statistics, meta-regression) and publication bias evaluation (Egger's test, trim-and-fill analysis). Sensitivity analyses included high-quality studies only and examined the influence of large database studies. Results Our analysis of 42 high-quality studies encompassing over 125,000 patients revealed profound and systematic cross-national disparities across multiple domains. In terms of care access, US patients demonstrated significantly higher hospice enrollment rates (28–35% vs. <1% in China, p < 0.001; HIGH certainty evidence) and greater access to specialized neuropalliative programs (15% of US centers vs. <1% in China). These differences translated into measurable quality of life disparities, with Chinese patients scoring 17.6 points worse on the PDQ-39 scale (95% CI 14.2–21.0; MODERATE certainty, I²=68%), a difference exceeding the minimal clinically important difference nearly four-fold. The burden on families showed equally striking patterns: Chinese families provided 94% of EOL care compared to 61% in the US, resulting in significantly higher caregiver depression rates (47% vs. 32%, OR = 1.89, 95% CI 1.45–2.47) and burden scores (Zarit difference: 10.2 points, 95% CI 7.8–12.6). Access to interventions revealed additional gaps, with only 9.2% of Chinese patients receiving physical therapy versus 14.4% in the US (OR = 0.61, 95% CI 0.49–0.76), and a 5.25-fold disparity in deep brain stimulation access (4.2% vs. 0.8%). Economic analysis demonstrated substantial out-of-pocket burden differences: Chinese families paid 58% of total costs ($4,200 annually) versus 12% for US families ($2,800). Meta-regression identified healthcare system characteristics as the primary driver of these disparities (R²=0.42, p < 0.001). Conclusions This comprehensive analysis reveals that systematic differences in healthcare infrastructure, insurance coverage, and cultural care models produce markedly divergent EOL experiences for PD patients in China versus the United States. These findings have immediate policy implications. For China, we recommend: (1) establishing pilot neuropalliative programs in tertiary centers with phased national expansion; (2) developing caregiver support infrastructure including respite care and training programs; (3) leveraging telemedicine platforms to address urban-rural disparities. For the United States, priorities include: (1) addressing racial disparities in rehabilitation access through culturally competent outreach; (2) expanding Medicare coverage for maintenance therapy; (3) earlier integration of neuropalliative care. Implementation science research is urgently needed to test culturally adapted interventions. As global PD prevalence accelerates, lessons from this bilateral comparison provide a framework for other nations confronting similar challenges in neurological care delivery.