Evaluation of age-related plantar-surface insensitivity and onset age of advanced insensitivity in older adults using vibratory and touch sensation tests

Age-related decline in plantar-surface sensitivity has been cited as one of the reasons for balance problems in older adults. This study investigated the level of plantar-surface sensitivity in older adults compared to young adults. Additionally, this study attempted to identify the onset age of advanced insensitivity in older adults and how well monofilament testing was able to predict insensitivity and onset age of advanced insensitivity. Vibration thresholds were assessed at four frequencies (3, 25, 100 and 250 Hz) and four foot sole locations (heel, first metatarsal, fifth metatarsal and great toe). Touch thresholds were evaluated with Semmes-Weinstein monofilaments at the same four locations. Results indicated that older adults showed insensitivity to vibratory (25 and 100 Hz) and touch stimuli when compared to young adults. Vibration testing at 100 Hz indicated that early in the seventh decade (72–73 years old) participants started to show a doubling of their detection threshold as compared to their younger counterparts (65–71 years old). Regression analysis indicated a significant predictive value of the monofilaments to 100 Hz vibration thresholds, but a caution is noted that this type of testing is not as sensitive to the onset of advanced plantar-surface insensitivity. Therefore, older adults have significant plantar-surface insensitivity as compared to young adults and have an onset of advanced insensitivity in the seventh decade of life. Monofilaments are useful to assess the age-related insensitivity but are not when attempting to identify the onset of advanced insensitivity.