Signal transmission in the brain propagates via distinct oscillatory frequency bands but the aperiodic component - 1/f activity - almost always co-exists which most of the previous studies have not sufficiently taken into consideration. We used a recently proposed parameterisation model that delimits the oscillatory and aperiodic components of neural dynamics on lifespan ageing data. Since, healthy ageing underlines an enormous change in local tissue properties, any systematic relationship of 1/f activity would highlight their impact on the self-organized critical functional states. Furthermore, we have used patterns of correlation between aperiodic background and metrics of behaviour, to understand the domain general effects of 1/f activity. We suggest that age-associated global change in 1/f baseline, alters the functional critical states of the brain affecting the global information processing impacting critically all aspects of cognition e.g., metacognitive awareness, speed of retrieval of memory, cognitive load and accuracy of recall through adult lifespan. This alteration in 1/f crucially impacts the oscillatory features peak frequency and band power ratio, which relates to more local processing and selective functional aspects of cognitive processing during the VSTM task. In summary, this study leveraging on big lifespan data for the first time tracks the cross-sectional lifespan associated periodic and aperiodic dynamical changes in the resting state to demonstrate how normative patterns of 1/f activity, peak frequency and band ratio measures provide distinct functional insights about the cognitive decline through adult lifespan.