From risk detection to brain health action: The CheckPD-CheckBRAIN pathway across the missing middle in Parkinson's disease.

Brain health has entered an implementation era, yet practical pathways for translating risk detection into meaningful action remain underdeveloped, particularly in low- and middle-income settings. Parkinson's disease (PD) offers a useful tracer condition for this challenge because it is common, progressive, clinically recognisable, functionally disabling, and highly sensitive to health-system capacity across awareness, referral, diagnosis, treatment, rehabilitation, caregiver support, and longitudinal monitoring. This review uses Thailand's CheckPD™ programme as an applied anchor for examining how digital PD screening can move beyond case-finding toward broader brain health implementation. CheckPD provides a population-facing digital screening and risk-stratification layer for PD and prodromal signals, but screening alone is insufficient. Without interpretation, risk communication, triage, referral completion, prevention advice, rehabilitation linkage, and follow-up, earlier detection may create earlier labelling rather than earlier benefit. We define this transition zone as the "missing middle." To address this gap, we propose CheckBRAIN™ as a post-screening brain health action framework organised around three domains: prevention pathways, resilience-building, and longitudinal brain health monitoring. Across primary prevention, CheckBRAIN promotes modifiable brain health and non-communicable disease risk reduction; across secondary prevention, it monitors risk trajectories, new prodromal symptoms, and conversion to clinical disease; and across tertiary prevention, it aims to preserve function, delay milestones, reduce complications, and support caregivers in established PD. By integrating prodromal PD risk science, digital screening, implementation science, resilience concepts, and global brain health strategy, the CheckPD-CheckBRAIN pathway offers a practical model for moving from early detection of neurodegeneration toward earlier, accessible, and actionable brain health care.