Cognitive decline and dementia have emerged as major challenges in modern healthcare with enormous associated societal and economic costs. Shifting demographics, owing to increasing numbers of people aged over 65 have greatly increased the potential scale of this problem in years to come. We report a novel quantitative method for assessment of cognitive decline (defined as a decline in mini mental state examination (MMSE) score of three or more) using quantitative parameters derived from body-worn inertial sensors. We sought to determine if baseline quantitative parameters and changes from baseline at follow-up, in those parameters could be used to automatically classify participants as cognitively declined or intact. Quantitative movement parameters were obtained at a baseline clinical assessment and in a follow-up assessment approximately 2 years later, using shank mounted triaxial gyroscopes. Data were obtained from 189 community dwelling older adults (aged over 60, 59 male, 130 female, mean age: 70.43 ± 6.57) while performing the timed up and go test. Nine participants who were deemed to be cognitively impaired at baseline (MMSE < 24) were excluded from analysis. Results suggest that quantitative parameters measured at baseline are 75.94% accurate in predicting cognitive decline in participants who were cognitively intact at baseline. A combination of baseline quantitative movement parameters and the change at follow-up (compared to baseline) in these parameters were 88.78% accurate in classifying final cognitive status in participants deemed cognitively intact at baseline. The reported method may be suitable for use as a portable cognitive screening tool, prompting further specialist clinical investigation and may also form part of a tool for longitudinal monitoring of cognitive function.