Validity of clinically derived cumulative somatosensory impairment index

Abstract

Design: Prospective cohort study.

Setting: Population-based cohort.

Participants: InCHIANTI ("Invecchiare in Chianti" or aging in the Chianti area) study participants (N=960; age, 21-91 y, 51.8% women).

Interventions: Not applicable.

Main outcome measures: The Cumulative Somatosensory Impairment Index was derived from baseline performance on clinical tests of pressure sensitivity, vibration sensitivity, proprioception, and graphesthesia. Global postural control was assessed using Frailty and Injuries Cooperative Studies of Intervention Techniques (FICSIT) balance test, time to complete 5 repeated chair stands, and fast walking speed, at baseline and at 3-year follow-up.

Results: In participants without neurologic conditions (n=799), the Cumulative Somatosensory Impairment Index was significantly different in age groups classified by decades (P<.001). Compared with participants without prevalent conditions, the Cumulative Somatosensory Impairment Index was significantly higher in persons with diabetes (P=.017), peripheral arterial disease (P=.006), and a history of stroke (P<.001). In the overall population (N=960), in the fully adjusted multiple regression models, the Cumulative Somatosensory Impairment Index independently predicted deterioration in FICSIT scores (P=.002), time for 5 repeated chair stands (P<.001), and fast gait speed (P=.003) at 3-year follow-up.

Conclusions: The Cumulative Somatosensory Impairment Index is a valid measure that detects relevant group differences in lower limb somatosensory impairment and is an independent predictor of decline in postural control over 3 years.

Fig 1

The graph denotes mean (95% confidence interval) Cumulative Somatosensory Impairment Index score of each age group (by decade) for cognitively intact participants. Participants with prevalent conditions that may impact peripheral neural function (eg, diabetes mellitus, peripheral arterial disease, stroke, Parkinson's disease, neuropathy) were excluded from this analysis (n=799). Cumulative Somatosensory Impairment Index was significantly higher for each decade after the fifth decade. The group-wise distribution of participants was as follows: >30y, 50; 30–39y, 60; 40–49y, 47; 50–59y, 58; 60–69y, 252; 70–79y, 270; 80–89y, 55; and >90y, 7. Abbreviation: CSII, Cumulative Somatosensory Impairment Index.

Fig 2

The scatterplots demonstrate the relation between performance on the postural control task at 3-year follow-up and regression standardized predicted values obtained from fully adjusted models. (A) FISCIT scores. (B) Repeated chair stand time. (C) Fast walking speed.

Fig 3

The bar graphs demonstrate average Cumulative Somato-sensory Impairment Index (standard error of the mean [SEM]) scores at baseline for quintiles of the performance on the postural control tasks at 3-year follow-up. (A) FISCIT scores. (B) Repeated chair stand time. (C) Fast walking speed. Abbreviation: CSII, Cumulative Somatosensory Impairment Index.