Human Neurologic Function and the Aging Process†

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Abstract
Sixty‐one normal men whose ages ranged from 20 to 80 years were evaluated on two occasions by means of a comprehensive series of 128 instrumented tests of neurologic function. The tests measured cognition, vision, strength, steadiness, reactions, speed, coordination, fatigue, gait, station, sensations, and tasks of daily living. The reliability of each test measure was determined, and any measure found unreliable (r ≤ 0.41) was not further analyzed. Significant age‐related linear decreases were found for almost all neurologic functions. The declines over the age span varied from less than 10 percent to more than 90 percent for different functions. For the upper extremities, the largest declines (> 50 percent) were in hand‐force steadiness, speed of hand‐arm movements, and vibration sense; for the lower extremities, the largest declines were in one‐legged balance with eyes closed and in vibration sense. For 13 of 14 tests in which significant dominant body‐side effects were found, larger losses in function with aging were observed on the dominant body side. Upon re‐testing 7–10 days later, the subjects improved their scores by more than 5 percent on only 17 tests, 9 of which concerned the activities of daily living. No significant differential learning effects were found across age groups. The results point to the importance of developing a data bank on age‐based neurologic function so that therapeutic effects can be evaluated in terms of age‐ and sex‐matched normal functioning.