The age-dependent deterioration in light touch sensation on the plantar aspect of the foot in a rural community in India: implications when screeningfor sensory impairment

Regular testing for impaired sensation is important in the management of di seases that can cause progressive nerve damage, such as leprosy. It has bee n shown that light touch sensibility decreases with age in the hands of hea lthy individuals, but little research has been undertaken to assess possibl e changes in the feet in developing countries. This information is needed t o allow an appropriate level of sensation to be chosen when screening for n erve damage in the foot. To clarify this, a cross-sectional study on male a dults was carried out in the rural town of Salur, Andhra Pradesh, India. A range of Semmes-Weinstein monofilaments were employed at 12 locations on th e foot to determine sensation to light touch stimuli in individuals from ea ch decade of adult life. It was found that in this population, sensibility threshold in the foot increases with age and this was noted in both soft an d callous skin. This shows the increase was due to neurological factors, no t merely due to an increase in callous deposition with advancing age. In th e majority of individuals in their fifties and sixties, the callous skin at the forefoot and heel was unable to detect the 5.07 monofilament (equivale nt to 8-12 g), previously recommended as a method to screen for plantar neu ropathy. All areas of all feet were able to detect the 5.46 filament (appro ximately 30 g). The size of this study (54 individuals) prevents the determ ination of definitive normal ranges for each decade of life in this populat ion. However, it does demonstrate the degree to which sensation deteriorate s with age and could be used as an approximate guide when interpreting the results of sensory testing in similar rural areas of the developing world.