Lifespan EEG Reference Charts Reveal Aperiodic Confounds in Beta-Band Biomarkers Across Neurological and Neuropsychiatric Disorders

Beta oscillations measured by scalp electroencephalography (EEG) are among the most prominent neural rhythms, implicated in motor control, cognition, and multiple neurological disorders, yet the absence of large-scale normative data and methodological inconsistency across studies has hindered the development of reliable reference frameworks necessary for clinical translation. These inconsistencies stem from two unresolved challenges: age-dependent neurophysiological changes that produce inherently non-linear beta trajectories across the lifespan, and the confounding influence of aperiodic 1/f activity in conventional beta analyses which changes independently with maturation and pathology. In this paper, we establish the first comprehensive lifespan reference charts for beta oscillations (N = 22,094, ages: 1-100 years) using complementary analytic approaches that isolate periodic oscillations from aperiodic background activity. We further quantify disorder-specific deviations in beta power and frequency across seven neuro-logical and neuropsychiatric disorders. Beta power showed a non-linear, tri-phasic trajectory, increasing through childhood and adolescence, peaking around age ~50 years, and declining in later life. Unadjusted and aperiodic-adjusted beta frequency showed opposing developmental trajectories; adjusted frequency revealed a previously uncharacterized adolescent dip, reaching minimum around ages 12-13 years, consistent across all brain lobes and both sexes. Beta power was reduced across most clinical groups, with effect sizes varying by disorder and brain lobe; schizophrenia spectrum disorders were a notable exception, showing reduced absolute but increased aperiodic-adjusted beta power -- a distinction undetectable without aperiodic decomposition. These reference charts demonstrate that aperiodic 1/f activity does not merely scale beta measurements but reverses their apparent developmental trajectory -- a systematic bias that, left unaccounted for, fundamentally misrepresents how beta frequency matures across the lifespan and obscures disorder-specific oscillatory signatures in clinical populations.