Reproducibility of peroneal motor nerve conduction measurement in older adults

Associations of Lower Extremity Peripheral Nerve Impairment and Risk of Dementia in Black and White Older Adults

BACKGROUND AND OBJECTIVES

Peripheral nerve impairments and dementia are common among older adults and share risk factors. However, few studies have examined whether peripheral nerve function and dementia are associated. We evaluated whether lower extremity peripheral nerve impairments were associated with higher incidence of dementia and whether associations differed by comorbidity subgroups (diabetes, low vitamin B12, and APOE ε4 allele carriers).

METHODS

We studied Black and White Health, Aging, and Body Composition Study participants 70 to 79 years of age and without dementia at enrollment. Lower extremity sensory and motor peripheral nerve function was measured at year 4 (the analytic baseline of this study). Sensory nerve impairments were measured with monofilament (1.4 g, 10 g) and vibration threshold of the toe. Monofilament insensitivity was defined as unable to detect monofilament (3 of 4 touches), and vibration detection impairment was defined as >130 μm. Fibular motor impairments were defined as <1 mV compound motor action potential (CMAP) amplitude and slow nerve conduction velocity <40 m/s. Incident dementia over the following 11 years was determined from medical records, cognitive scores, and medications. Cox proportional hazard models adjusted for demographics and health conditions assessed associations of nerve impairments with incident dementia.

RESULTS

Among 2,174 participants (52% women, 35% Black), 45% could not detect monofilament 1.4 g, 9% could not detect monofilament 10 g, 6% could not feel vibration, 10% had low CMAP amplitude, and 24% had slow conduction velocity. Monofilament 10 g (hazard ratio [HR] 1.35, 95% CI 0.99-1.84) and vibration detection insensitivity (HR 1.73, 95% CI 1.24-2.40) were associated/borderline associated with a higher risk of dementia after covariate adjustment. Estimates were elevated but not significant for monofilament 1.4 g, CMAP amplitude, and conduction velocity (p > 0.05). Increasing number of peripheral nerve impairments was associated with higher risk of dementia in a graded fashion; for ≥3 impairments, the HR was 2.37 (95% CI 1.29-4.38). In subgroup analyses, effect estimates were generally higher among those with diabetes, low vitamin B12, and APOE ε4 allele except for vibration detection.

DISCUSSION

Peripheral nerve impairments, especially sensory, were associated with a higher risk of dementia even after adjustment for age and other health factors. These associations may represent a shared susceptibility to nervous system degeneration.

Persistent polypharmacy and fall injury risk: the Health, Aging and Body Composition Study

BACKGROUND

Older adults receive treatment for fall injuries in both inpatient and outpatient settings. The effect of persistent polypharmacy (i.e. using multiple medications over a long period) on fall injuries is understudied, particularly for outpatient injuries. We examined the association between persistent polypharmacy and treated fall injury risk from inpatient and outpatient settings in community-dwelling older adults.

METHODS

The Health, Aging and Body Composition Study included 1764 community-dwelling adults (age 73.6 ± 2.9 years; 52% women; 38% black) with Medicare Fee-For-Service (FFS) claims at or within 6 months after 1998/99 clinic visit. Incident fall injuries (N = 545 in 4.6 ± 2.9 years) were defined as the initial claim with an ICD-9 fall E-code and non-fracture injury, or fracture code with/without a fall code from 1998/99 clinic visit to 12/31/08. Those without fall injury (N = 1219) were followed for 8.1 ± 2.6 years. Stepwise Cox models of fall injury risk with a time-varying variable for persistent polypharmacy (defined as ≥6 prescription medications at the two most recent consecutive clinic visits) were adjusted for demographics, lifestyle characteristics, chronic conditions, and functional ability. Sensitivity analyses explored if persistent polypharmacy both with and without fall risk increasing drugs (FRID) use were similarly associated with fall injury risk.

RESULTS

Among 1764 participants, 636 (36%) had persistent polypharmacy over the follow-up period, and 1128 (64%) did not. Fall injury incidence was 38 per 1000 person-years. Persistent polypharmacy increased fall injury risk (hazard ratio [HR]: 1.31 [1.06, 1.63]) after adjusting for covariates. Persistent polypharmacy with FRID use was associated with a 48% increase in fall injury risk (95%CI: 1.10, 2.00) vs. those who had non-persistent polypharmacy without FRID use. Risks for persistent polypharmacy without FRID use (HR: 1.22 [0.93, 1.60]) and non-persistent polypharmacy with FRID use (HR: 1.08 [0.77, 1.51]) did not significantly increase compared to non-persistent polypharmacy without FRID use.

CONCLUSIONS

Persistent polypharmacy, particularly combined with FRID use, was associated with increased risk for treated fall injuries from inpatient and outpatient settings. Clinicians may need to consider medication management for FRID and other fall prevention strategies in community-dwelling older adults with persistent polypharmacy to reduce fall injury risk.

Swallowing impairment in older adults: association with sensorimotor peripheral nerve function from the Health, Aging and Body Composition study

BACKGROUND

The purpose of this study was to examine whether impairments in sensorimotor peripheral nerve function are associated with a higher likelihood of swallowing impairment in older adults.

METHODS

Health, Aging and Body Composition participants (n = 607, age = 75.8 ± 2.7 years, 55.8% women, 32.3% black) underwent peripheral nerve testing at Year 4 and 11 with swallowing difficulty assessed at Year 4 and 15. Nerve conduction amplitude and velocity were measured at the peroneal motor nerve. Sensory nerve function was assessed with the vibration detection threshold and monofilament (1.4-g/10-g) testing at the big toe. Symptoms of lower extremity peripheral neuropathy and difficulty swallowing were collected by self-report. Data analysis was performed using a hierarchical approach. Odds ratios (ORs) were estimated using non-conditional logistic regression.

RESULTS

At Year 15 108 (17.8%) participants had swallowing impairments. In fully adjusted models, the peripheral nerve impairments associated with swallowing impairment were numbness (OR 4.67; 95%CI 2.24-9.75) and poor motor nerve conduction velocity (OR 2.26; 95%CI 1.08-4.70). Other peripheral nerve impairments were not related to swallowing.

CONCLUSIONS

The association between slow motor nerve conduction velocity and numbness and a higher likelihood of swallowing difficulties a decade later in our prospective study identifies an important area for further investigation in older adults.

Chronic kidney disease as a risk factor for peripheral nerve impairment in older adults: A longitudinal analysis of Health, Aging and Body Composition (Health ABC) study

Introduction

Sensory and motor nerve deficits are prevalent in older adults and are associated with loss of functional independence. We hypothesize that chronic kidney disease predisposes to worsening sensorimotor nerve function over time.

Materials and methods

Participants were from the Health, Aging and Body Composition Study (N = 1121) with longitudinal data between 2000–01 (initial visit) and 2007–08 (follow-up visit). Only participants with non-impaired nerve function at the initial visit were included. The predictor was presence of CKD (estimated GFR ≤ 60 ml/min/1.73m²) from the 1999–2000 visit. Peripheral nerve function outcomes at 7-year follow-up were 1) Motor: “new” impairments in motor parameters (nerve conduction velocity NCV < 40 m/s or peroneal compound motor action potential < 1 mv) at follow-up, and 2) Sensory: “new” impairment defined as insensitivity to standard 10-g monofilament or light 1.4-g monofilament at the great toe and “worsening” as a change from light to standard touch insensitivity over time. The association between CKD and “new” or “worsening” peripheral nerve impairment was studied using logistic regression.

Results

The study population was 45.9% male, 34.3% Black and median age 75 y. CKD participants (15.6%) were older, more hypertensive, higher in BMI and had 2.37 (95% CI 1.30–4.34) fold higher adjusted odds of developing new motor nerve impairments in NCV. CKD was associated with a 2.02 (95% CI 1.01–4.03) fold higher odds of worsening monofilament insensitivity. CKD was not associated with development of new monofilament insensitivity.

Conclusions

Pre-existing CKD leads to new and worsening sensorimotor nerve impairments over a 7-year time period in community-dwelling older adults.

Chronic kidney disease and peripheral nerve function in the Health, Aging and Body Composition Study

BACKGROUND

Chronic kidney disease (CKD) is associated with poor mobility. Peripheral nerve function alterations play a significant role in low mobility. We tested the hypothesis that early CKD is associated with altered sensory, motor and autonomic nerve function.

METHODS

Participants in the Health, Aging and Body Composition cohort who had kidney function measures in Year 3 (1999-2000) and nerve function measurements at Year 4 (2000-01) were analyzed (n = 2290). Sensory (vibration threshold, monofilament insensitivity to light and standard touch), motor [compound motor action potentials (CMAPs), nerve conduction velocities (NCVs)] and autonomic (heart rate response and recovery after a 400-m walk test) nerve function as well as participant characteristics were compared across cystatin C- and creatinine-based estimated glomerular filtration rate categorized as ≤60 (CKD) or >60 mL/min/1.73 m2 (non-CKD). The association between CKD and nerve function was examined with logistic regression adjusted for covariates.

RESULTS

Participants with CKD (n = 476) were older (77 ± 3 versus 75 ± 3 years; P < 0.05) and had a higher prevalence of diabetes (20.6% versus 13.1%; P < 0.001). CKD was associated with higher odds for vibration detection threshold {odds ratio [OR] 1.7 [95% confidence interval (CI) 1.1-2.7]} and light touch insensitivity [OR 1.4 (95% CI 1.1-1.7)]. CMAPs and NCVs were not significantly different between CKD and non-CKD patients. In adjusted analyses, participants with CKD had higher odds of an abnormal heart rate response [OR 1.6 (95% CI 1.1-2.2)] and poor heart rate recovery [OR 1.5 (95% CI 1.1-2.0)].

CONCLUSIONS

CKD is associated with changes in sensory and autonomic nerve function, even after adjustment for demographics and comorbidities, including diabetes. Longitudinal studies in CKD are needed to determine the contribution of nerve impairments to clinically important outcomes.

Residential Proximity to Agricultural Fields and Neurological and Mental Health Outcomes in Rural Adults in Matlab, Bangladesh

Pesticide exposure is an important rural public health concern that is linked to a spectrum of health outcomes in farmers. However, little is known about these effects on residents living in close proximity to agricultural fields and who are not involved in regular farming. This paper compared the effects of residential proximity to farming lands on a number of neurological and mental health outcomes in adults. A cross-sectional study was performed on 57 adults involved in farming only occasionally in rural Matlab in Bangladesh. A health and demographic surveillance system (HDSS) and geocoding were used to define proximity to the agricultural field. Neurological health was measured using the trail making test, vibrotactile threshold measurement, and dominant ulnar nerve conduction velocity (NCV) amplitude. An adapted Center for Epidemiological Studies Depression scale (CES-D) questionnaire was used to evaluate mental health. Results indicated that respondents living near agricultural fields had significantly higher vibrotactile threshold in big toes (p < 0.004) and needed a longer time to complete the trail making test (p < 0.004) than those living far from fields after accounting for the covariates. Results of this pilot study suggest further investigations to establish the impact of pesticide exposure among occasional and non-farmers on neurological health outcomes.

Motor amplitudes may predict electromyography-confirmed radiculopathy in patients referred for radiating limb pain

INTRODUCTION

Radiculopathy is diagnosed by needle electromyography, with nerve conduction studies excluding alternative diagnoses.

METHODS

In patients referred for electrodiagnostic evaluation of radiating limb pain, we compared ulnar motor amplitudes between those with and without electromyographically confirmed C8 radiculopathy, as well as fibular motor amplitudes between those with and without electromyographically confirmed L5 radiculopathy.

RESULTS

Patients with electromyographically confirmed C8 or L5 radiculopathy demonstrated decreased ulnar or fibular motor amplitudes, respectively, as compared to patients without radiculopathy. Receiver operating characteristic curves demonstrated good diagnostic accuracy, with areas under the curve of 0.85 and 0.82, respectively. Optimal cut-offs for electromyographically confirmed C8 and L5 radiculopathies were 10.2 mV and 3.6 mV, respectively, with associated sensitivities/specificities of 0.86/0.74 and 0.92/0.60.

DISCUSSION

Ulnar and fibular motor amplitudes may have clinical utility in assessing the likelihood of patients demonstrating electromyographically confirmed C8 and L5 radiculopathies with active denervation. The findings may be particularly useful in patients intolerant of needle electromyography. Muscle Nerve 59:561-561, 2019.

Neuromuscular electrical stimulation is ineffective for treating quadriceps muscle wasting with ruptured aneurysm: A case report

Introduction

Neuromuscular electrical stimulation (NMES) is a preventive intervention for muscle wasting in patients with aneurysms during the acute phase; however, its efficacy still remains unclear. In this case study, we report the effects of NMES on quadriceps muscle wasting for a patient with ruptured middle cerebral artery aneurysms during the acute phase.

Presentation of case

A 66-year-old woman was admitted because of a ruptured middle cerebral artery aneurysm resulting from intracerebral hematoma with subarachnoid hemorrhage. The following day, the patient started undergoing 60–120-min NMES treatment for both her quadriceps muscles, which was continued for 10 days in 2 weeks. Quadriceps muscle thickness as measured by ultrasonography was decreased in both sides (26% and 35% for the right and left sides, respectively). The compound muscle action potential (CMAP) amplitude in the peroneal nerve was also decreased in both sides (73% vs 76%).

Discussion

The lack of efficacy of NMES in preventing muscle wasting is the decreased CMAP amplitude in this patient, which showed the possibility of existence of critical illness polyneuropathy.

Conclusion

NMES had no effect on quadriceps muscle wasting in a patient with ruptured middle cerebral artery aneurysms who had decreased CMAP amplitude in the peroneal nerve during the acute phase. NMES is not effective for patients with peripheral nerve conduction abnormalities.

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NMES is not effective for preventing muscle wasting and disability.

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NMES is not effective for patients with peripheral nerve conduction abnormalities.

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The efficacy of NMES is dependent on whether conduction abnormalities exist.

Low blood pressure levels for fall injuries in older adults: the Health, Aging and Body Composition Study

Fall injuries cause morbidity and mortality in older adults. We assessed if low blood pressure (BP) is associated with fall injuries, including sensitivity analyses stratified by antihypertensive medications, in community-dwelling adults from the Health, Aging and Body Composition Study (N = 1819; age 76.6 ± 2.9 years; 53% women; 37% black). Incident fall injuries (N = 570 in 3.8 ± 2.4 years) were the first Medicare claims event from clinic visit (7/00-6/01) to 12/31/08 with an ICD-9 fall code and non-fracture injury code, or fracture code with/without a fall code. Participants without fall injuries (N = 1249) were censored over 6.9 ± 2.1 years. Cox regression models for fall injuries with clinically relevant systolic BP (SBP; ≤ 120, ≤ 130, ≤ 140, > 150 mmHg) and diastolic BP (DBP; ≤ 60, ≤ 70, ≤ 80, > 90 mmHg) were adjusted for demographics, body mass index, lifestyle factors, comorbidity, and number and type of medications. Participants with versus without fall injuries had lower DBP (70.5 ± 11.2 vs. 71.8 ± 10.7 mmHg) and used more medications (3.8 ± 2.9 vs. 3.3 ± 2.7); all P < 0.01. In adjusted Cox regression, fall injury risk was increased for DBP ≤ 60 mmHg (HR = 1.25; 95% CI 1.02-1.53) and borderline for DBP ≤ 70 mmHg (HR = 1.16; 95% CI 0.98-1.37), but was attenuated by adjustment for number of medications (HR = 1.22; 95% CI 0.99-1.49 and HR = 1.12; 95% CI 0.95-1.32, respectively). Stratifying by antihypertensive medication, DBP ≤ 60 mmHg increased fall injury risk only among those without use (HR = 1.39; 95% CI 1.02-1.90). SBP was not associated with fall injury risk. Number of medications or underlying poor health may account for associations of low DBP and fall injuries.

Relationship between sensorimotor peripheral nerve function and indicators of cardiovascular autonomic function in older adults from the Health, Aging and Body Composition Study

BACKGROUND

Age-related peripheral nervous system (PNS) impairments are highly prevalent in older adults. Although sensorimotor and cardiovascular autonomic function have been shown to be related in persons with diabetes, the nature of the relationship in general community-dwelling older adult populations is unknown.

METHODS

Health, Aging and Body Composition participants (n=2399, age=76.5±2.9years, 52% women, 38% black) underwent peripheral nerve testing at the 2000/01 clinic visit. Nerve conduction amplitude and velocity were measured at the peroneal motor nerve. Sensory nerve function was assessed with vibration detection threshold and monofilament (1.4-g/10-g) testing at the big toe. Symptoms of lower-extremity peripheral neuropathy were collected by self-report. Cardiovascular autonomic function indicators included postural hypotension, resting heart rate (HR), as well as HR response to and recovery from submaximal exercise testing (400m walk). Multivariable modeling adjusted for demographic/lifestyle factors, medication use and comorbid conditions.

RESULTS

In fully adjusted models, poor motor nerve conduction velocity (<40m/s) was associated with greater odds of postural hypotension, (OR=1.6, 95% CI: 1.0-2.5), while poor motor amplitude (<1mV) was associated with 2.3beats/min (p=0.003) higher resting HR. No associations were observed between sensory nerve function or symptoms of peripheral neuropathy and indicators of cardiovascular autonomic function.

CONCLUSIONS

Motor nerve function and indicators of cardiovascular autonomic function remained significantly related even after considering many potentially shared risk factors. Future studies should investigate common underlying processes for developing multiple PNS impairments in older adults.

Sensorimotor Peripheral Nerve Function and the Longitudinal Relationship With Endurance Walking in the Health, Aging and Body Composition Study

OBJECTIVES

To determine whether lower extremity sensorimotor peripheral nerve deficits are associated with reduced walking endurance in older adults.

DESIGN

Prospective cohort study with 6 years of follow-up.

SETTING

Two university research clinics.

PARTICIPANTS

Community-dwelling older adults enrolled in the Health, Aging and Body Composition Study from the 2000-2001 annual clinical examination (N=2393; mean age ± SD, 76.5±2.9y; 48.2% men; 38.2% black) and a subset with longitudinal data (n=1178).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Participants underwent peripheral nerve function examination in 2000-2001, including peroneal motor nerve conduction amplitude and velocity, vibration perception threshold, and monofilament testing. Symptoms of lower extremity peripheral neuropathy included numbness or tingling and sudden stabbing, burning, pain, or aches in the feet or legs. The Long Distance Corridor Walk (LDCW) (400 m) was administered in 2000-2001 and every 2 years afterward for 6 years to assess endurance walking performance over time.

RESULTS

In separate, fully adjusted linear mixed models, poor vibration threshold (>130 μm), 10-g and 1.4-g monofilament insensitivity were each associated with a slower 400-m walk completion time (16.0 s, 14.4s, and 6.9 s slower, respectively; P<.05 for each). Poor motor amplitude (<1 mV), poor vibration perception threshold, and 10-g monofilament insensitivity were related to greater slowing per year (4.7, 4.2, and 3.8 additional seconds per year, respectively; P<.05), although poor motor amplitude was not associated with initial completion time.

CONCLUSIONS

Poorer sensorimotor peripheral nerve function is related to slower endurance walking and greater slowing longitudinally. Interventions to reduce the burden of sensorimotor peripheral nerve function impairments should be considered to help older adults maintain walking endurance-a critical component for remaining independent in the community.

Mobility-Related Consequences of Reduced Lower-Extremity Peripheral Nerve Function with Age: A Systematic Review

The objective of this study is to systematically review the relationship between lower-extremity peripheral nerve function and mobility in older adults. The National Library of Medicine (PubMed) was searched on March 23, 2015 with no limits on publication dates. One reviewer selected original research studies of older adults (≥65 years) that assessed the relationship between lower-extremity peripheral nerve function and mobility-related outcomes. Participants, study design and methods of assessing peripheral nerve impairment were evaluated and results were reported and synthesized. Eight articles were identified, including 6 cross-sectional and 2 longitudinal studies. These articles investigated 6 elderly cohorts (4 from the U.S. and 2 from Italy): 3 community-dwelling (including 1 with only disabled women and 1 without mobility limitations at baseline), 1 with both community-dwelling and institutionalized residents, 1 from a range of residential locations, and 1 of patients with peripheral arterial disease. Mean ages ranged from 71-82 years. Nerve function was assessed by vibration threshold (n=2); sensory measures and clinical signs and symptoms of neuropathy (n=2); motor nerve conduction (n=1); and a combination of both sensory measures and motor nerve conduction (n=3). Each study found that worse peripheral nerve function was related to poor mobility, although relationships varied based on the nerve function measure and mobility domain assessed. Six studies found that the association between nerve function and mobility persisted despite adjustment for diabetes. Evidence suggests that peripheral nerve function impairment at various levels of severity is related to poor mobility independent of diabetes. Relationships varied depending on peripheral nerve measure, which may be particularly important when investigating specific biological mechanisms. Future research needs to identify risk factors for peripheral nerve decline beyond diabetes, especially those common in late-life and modifiable. Interventions to preserve nerve function should be investigated with regard to their effect on postponing or preventing disability in older adults.

Sensory and motor peripheral nerve function and incident mobility disability

OBJECTIVES

To assess the relationship between sensorimotor nerve function and incident mobility disability over 10 years.

DESIGN

Prospective cohort study with longitudinal analysis.

SETTING

Two U.S. clinical sites.

PARTICIPANTS

Population-based sample of community-dwelling older adults with no mobility disability at 2000/01 examination (N = 2,148 [Corrected]; mean age ± SD 76.5 ± 2.9, body mass index 27.1 ± 4.6; 50.2% female, 36.6% black, 10.7% with diabetes mellitus).

MEASUREMENTS

Motor nerve conduction amplitude (poor <1 mV) and velocity (poor <40 m/s) were measured on the deep peroneal nerve. Sensory nerve function was measured using 10- and 1.4-g monofilaments and vibration detection threshold at the toe. Lower extremity symptoms included numbness or tingling and aching or burning pain. Incident mobility disability assessed semiannually over 8.5 years (interquartile range 4.5-9.6 years) was defined as two consecutive self-reports of a lot of difficulty or inability to walk one-quarter of a mile or climb 10 steps.

RESULTS

Nerve impairments were detected in 55% of participants, and 30% developed mobility disability. Worse motor amplitude (HR = 1.29 per SD, 95% CI = 1.16-1.44), vibration detection threshold (HR = 1.13 per SD, 95% CI = 1.04-1.23), symptoms (HR = 1.65, 95% CI = 1.26-2.17), two motor impairments (HR = 2.10, 95% CI = 1.43-3.09), two sensory impairments (HR = 1.91, 95% CI = 1.37-2.68), and three or more nerve impairments (HR = 2.33, 95% CI = 1.54-3.53) predicted incident mobility disability after adjustment. Quadriceps strength mediated relationships between certain nerve impairments and mobility disability, although most remained significant.

CONCLUSION

Poor sensorimotor nerve function independently predicted mobility disability. Future work should investigate modifiable risk factors and interventions such as strength training for preventing disability and improving function in older adults with poor nerve function.

Mitochondrial DNA Sequence Variation Associated With Peripheral Nerve Function in the Elderly

BACKGROUND

Mitochondrial dysfunction is a prominent hallmark of many sensory neuropathies. The purpose of this study was to assess the influence of mitochondrial DNA sequence variation on peripheral nerve function in the population-based Health, Aging, and Body Composition Study.

METHODS

We investigated the role of common mitochondrial DNA variation (n = 1,580) and complete mitochondrial DNA sequences (n = 138) on peroneal motor nerve conduction velocity and amplitude, average vibration detection threshold, and monofilament sensitivity.

RESULTS

Nominal associations among common mitochondrial DNA variants and haplogroups were identified but were not statistically significant after adjustment for multiple comparisons. Sequence-based approaches were used to identify aggregate variant associations across the 16S rRNA (weighted-sum, p = 2E-05 and variable threshold, p = 9E-06) for nerve conduction velocity. Several of these rare 16S variants occurred at or near sites with earlier disease associations and are also in close proximity to the peptidyl transferase center, which is the catalytic center of the 16S rRNA CONCLUSIONS: These results suggest that sequence variation related to mitochondrial protein synthesis/assembly is associated with peripheral nerve function and may provide insight into targets for intervention or new clinical strategies to preserve nerve function in late life.

Sensory and motor peripheral nerve function and longitudinal changes in quadriceps strength

BACKGROUND

Poor peripheral nerve function is common in older adults and may be a risk factor for strength decline, although this has not been assessed longitudinally.

METHODS

We assessed whether sensorimotor peripheral nerve function predicts strength longitudinally in 1,830 participants (age = 76.3 ± 2.8, body mass index = 27.2 ± 4.6kg/m(2), strength = 96.3 ± 34.7 Nm, 51.0% female, 34.8% black) from the Health ABC study. Isokinetic quadriceps strength was measured semiannually over 6 years. Peroneal motor nerve conduction amplitude and velocity were recorded. Sensory nerve function was assessed with 10-g and 1.4-g monofilaments and average vibration detection threshold at the toe. Lower-extremity neuropathy symptoms were self-reported.

RESULTS

Worse vibration detection threshold predicted 2.4% lower strength in men and worse motor amplitude and two symptoms predicted 2.5% and 8.1% lower strength, respectively, in women. Initial 10-g monofilament insensitivity predicted 14.2% lower strength and faster strength decline in women and 6.6% lower strength in men (all p < .05).

CONCLUSION

Poor nerve function predicted lower strength and faster strength decline. Future work should examine interventions aimed at preventing declines in strength in older adults with impaired nerve function.

Peripheral nerve function and lower extremity muscle power in older men

OBJECTIVE

To assess whether sensorimotor peripheral nerve function is associated with muscle power in community-dwelling older men.

DESIGN

Longitudinal cohort study with 2.3±0.3 years of follow-up.

SETTING

One clinical site.

PARTICIPANTS

Participants (n=372; mean age ± SD, 77.2±5.1y; 99.5% white; body mass index, 27.9±3.7kg/m(2); power, 1.88±0.6W/kg) at 1 site of the Osteoporotic Fractures in Men Study (N=5994).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

A nerve function ancillary study was performed 4.6±0.4 years after baseline. Muscle power was measured using a power rig. Peroneal motor nerve conduction amplitude, distal motor latency, and mean f-wave latency were measured. Sensory nerve function was assessed using 10-g and 1.4-g monofilaments and sural sensory nerve conduction amplitude and distal latency. Peripheral neuropathy symptoms at the leg and feet were assessed by self-report.

RESULTS

After adjustments for age, height, and total body lean and fat mass, 1 SD lower motor (β=-.07, P<.05) and sensory amplitude (β=-.09, P<.05) and 1.4-g (β=-.11, P<.05) and 10-g monofilament insensitivity (β=-.17, P<.05) were associated with lower muscle power/kg. Compared with the effect of age on muscle power (β per year, -.05; P<.001), this was equivalent to aging 1.4 years for motor amplitude, 1.8 years for sensory amplitude, 2.2 years for 1.4-g monofilament detection, and 3.4 years for 10-g detection. Baseline 1.4-g monofilament detection predicted a greater decline in muscle power/kg. Short-term change in nerve function was not associated with concurrent short-term change in muscle power/kg.

CONCLUSIONS

Worse sensory and motor nerve function were associated with lower muscle power/kg and are likely important for impaired muscle function in older men. Monofilament sensitivity was associated with a greater decline in muscle power/kg, and screening may identify an early risk for muscle function decline in late life, which has implications for disability.