Sensory and motor peripheral nerve function and lower-extremity quadriceps strength: the health, aging and body composition study

Abstract

Objectives: To determine whether sensory and motor nerve function is associated cross-sectionally with quadriceps or ankle dorsiflexion strength in an older community-based population.

Design: Cross-sectional analyses within a longitudinal cohort study.

Setting: Two U.S. clinical sites.

Participants: Two thousand fifty-nine Health, Aging and Body Composition Study (Health ABC) participants (49.5% male, 36.7% black, aged 73-82) in 2000/01.

Measurements: Quadriceps and ankle strength were measured using an isokinetic dynamometer. Sensory and motor peripheral nerve function in the legs and feet was assessed using 10-g and 1.4-g monofilaments, vibration threshold, and peroneal motor nerve conduction amplitude and velocity.

Results: Monofilament insensitivity, poorest vibration threshold quartile (>60 mu), and poorest motor nerve conduction amplitude quartile (<1.7 mV) were associated with 11%, 7%, and 8% lower quadriceps strength (all P<.01), respectively, than in the best peripheral nerve function categories in adjusted linear regression models. Monofilament insensitivity and lowest amplitude quartile were both associated with 17% lower ankle strength (P<.01). Multivariate analyses were adjusted for demographic characteristics, diabetes mellitus, body composition, lifestyle factors, and chronic health conditions and included all peripheral nerve measures in the same model. Monofilament insensitivity (beta=-7.19), vibration threshold (beta=-0.097), and motor nerve conduction amplitude (beta=2.01) each contributed independently to lower quadriceps strength (all P<.01). Monofilament insensitivity (beta=-5.29) and amplitude (beta=1.17) each contributed independently to lower ankle strength (all P<.01). Neither diabetes mellitus status nor lean mass explained the associations between peripheral nerve function and strength.

Conclusion: Reduced sensory and motor peripheral nerve function is related to poorer lower extremity strength in older adults, suggesting a mechanism for the relationship with lower extremity disability.

Figure 1

Difference in quadriceps strength* by peripheral nerve function measures^§. *Adjusted for age, sex, race, clinic site, diabetes, height, total lean and fat mass † p<0.01 pairwise comparison with 1st group ‡ p<0.01 pairwise comparison with 2^nd group ^§ Monofilament groups (left to right): None, 10-g, 1.4-g; Vibration threshold quartiles (left to right): 60-120μ, 30-50 μ, 10-20μ, 0μ; Amplitude quartiles (left to right): <1.7mV, 1.7-3.0 mV, 3.1-4.5 mV, >4.5 mV; Velocity quartiles (left to right): <39.3 m/s, 39.3-43.0 m/s, 43.1-46.8m/s, >46.8 m/s