Two-point discrimination test of the skin as an index of sensory aging

Although the two-point discrimination test of the skin is a simple test of the sensory nerve function, there have been few studies on age-related changes in the ability to discriminate between two points in a large noninstitutionalized population. In this study we attempted (1) to determine normal values on the two-point discrimination test by age and gender in a large population with a wide age span; (2) to describe age-related changes on the two-point discrimination test; and (3) to test the independence of this index from other indices measuring physiological aging by sensory functions, such as accommodation and hearing tests. The subjects were 2,036 men and women aged 10-87 years. The minimal distance at which two points could be discriminated was measured longitudinally on a line from the palmar pad to the base of the index finger of the right hand. The two points of a caliper were applied at the same time (stationary two-point discrimination test) using the weight of the caliper alone. An age-related decline in the ability to discriminate two points was apparent, but there were no significant differences in ability between men and women. The minimal distance of discrimination on the hand increased almost linearly between 10 and 60 years of age. The results of the two-point discrimination test of the skin were independent of those of visual accommodation tests and hearing loss of high-frequency sound. From these results, the two-point discrimination test of the skin can be used as a powerful and simple index of sensory aging.