Parkinson’s disease is the second most common neurodegenerative disorder in the world and is the fastest-growing neurological condition worldwide. Its classic hallmarks - resting tremor, bradykinesia, and rigidity usually lead to diagnosis only after extensive dopaminergic neuronal loss has already happened. Newer research, however, highlights a prodromal window that might open decades earlier. There’s an increasing theory that pathological changes of the nervous system could start in a person’s 20s. This means that early detection is not just desirable but could be transformative for clinical outcomes.Individuals with PD at prodromal and early motor stages alike report symptoms in multiple domains, including behavioral, cognitive, autonomic, sensory, sleep-related, and activities of daily living. Most of these symptoms are subtle and overlap with common conditions, so they aren’t often recognized or are mistaken for ageing, stress or other lifestyle factors. So, identifying consistent patterns amid daily behavioral variations is crucial for improving early PD detection.Sleep Disturbances: An Early Warning SignOne of the most robust prodromal markers is REM sleep behavior disorder (RBD). People who are affected have sleep disruption, physically act out their dreams during REM phase (acting out dreams), and vivid dream life and some through sleepwalking — all of them worthy substrates for signals of early brainstem pathology.Loss of Smell May Appear Years Before DiagnosisAnosmia, a partial or complete loss of the sense of smell, could be PD’s earliest recognizable sign, occurring as much as 10 years before motor signs become apparent. In practice, this means being unable to easily perceive familiar smells like food or coffee. Because this symptom manifests so early and appears so unrelated to the health of the brain, it is rarely taken seriously in clinical practice. Gut Changes and the Brain ConnectionChronic constipation is a common prodromal symptom indicating reduced gut motility that can predate motor symptoms by years. This observation is consistent with the gut–brain axis hypothesis: gut microbiota dysbiosis disrupts gastrointestinal motility, permeability and inflammation, which may facilitate a prion-like transmission of misformed alpha-synuclein (α-syn) from gut to brain through the enteric nervous system.1 further underscoring the biomarker potential of gastrointestinal symptoms with clinical relevance. Subtle Changes in Movement and MoodBefore tremors are apparent, there can be subtle changes in fine motor control. Trouble with tasks such as handwriting, using electronic devices or manipulating small objects, along with uncharacteristic anxiety or a low mood, can serve as signals of the preclinical stage. Micrographia (progressively smaller and cramped handwriting) is a particularly telling sign from daily life that deserves a neurological workup when it appears without an obvious cause.Fatigue and Autonomic Symptoms Can Precede Motor SignsFatigue that never seems to get better with rest affects work performance, social engagement and daily motivation, and can occur long before an official diagnosis. More than half of all PD patients develop at least one form of autonomic dysfunction, which can precede motor symptoms by four years or more, and is now being recognized as a key prognostic biomarker for prodromal PD. Cardiovascular instability, orthostatic hypotension, and urinary irregularities further influence how individuals navigate everyday environments long before a definitive diagnosis is made.Recognizing Early Signals Can Transform CareThe evidence reviewed here collectively supports a paradigm shift: Parkinson's disease is best defined as systemic, progressive, and with recognizable signals in daily life long before motor signs of decline. Disrupted sleep, anosmia, gastrointestinal changes, fine motor difficulties and chronic fatigue are not complaints in a vacuum; they are potential early signs of a neurological process left unsupervised and now in motion. Incorporating routine clinical assessment of these behavioural precursors and pre-motor signs would allow us to meaningfully extend the opportunity for therapeutic intervention, which could in turn improve patient outcomes across a broad range of CNS disorders.