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Biomedical subjects

R S Lockwood

Publications and source records attributed to R S Lockwood.

14 recordsLinked to original sources
PubMed1998

Natural history of median nerve sensory conduction in industry: relationship to symptoms and carpal tunnel syndrome in 558 hands over 11 years.

We evaluated the natural history of median nerve sensory conduction, hand/wrist symptoms, and carpal tunnel syndrome (CTS) in an 11-year longitudinal study of 289 workers from four industries. Twenty hands which had carpal tunnel release surgery were excluded, leaving 558 hands for the primary study group. Overall, the trend was for mean sensory latencies and prevalence of slowing to increase, the prevalence of symptoms to decrease, and the prevalence of CTS to remain unchanged. Among individual hands, nerve conduction abnormalities tended to persist (82% 11-year persistence), while symptoms fluctuated widely (13% 11-year persistence). There was a strong, direct linear correlation between initial severity of slowing and subsequent development of CTS; however, most workers who developed de novo slowing did not develop symptoms or CTS. We conclude that changes in conduction status of the median nerve occur naturally with increasing age and do not necessarily lead to symptoms and CTS.

Adult↗
PubMed1997

Vitamin B6, vitamin C, and carpal tunnel syndrome. A cross-sectional study of 441 adults.

As part of an ongoing study of carpal tunnel syndrome (CTS) in industry, we measured plasma concentrations of pyridoxal 5'-phosphate (PLP, a measure of vitamin B6 status) and total ascorbate (ASC, a measure of vitamin C status) in 441 adult volunteers from six industries and a university exercise study. In the entire study group and in non-vitamin users (n = 218), there were no significant differences in mean plasma PLP or ASC concentrations between controls (neither symptoms nor slowing), subjects with symptoms only, subjects with median nerve slowing only, or subjects with CTS (symptoms + slowing). In male non-vitamin users (n = 137), there were significant inverse univariate associations between plasma PLP concentration and the prevalence of pain, the frequency of tingling and nocturnal awakening, and the Phalen test result. In this same subgroup, the ASC/PLP ratio was directly associated with the prevalence of pain and nocturnal awakening, and with the frequency of pain, tingling, and nocturnal awakening. In multivariate analyses, plasma ASC concentration predicted more median nerve slowing and confirmed CTS, and vitamin or vitamin interaction variables were independent predictors of 20 CTS-related outcomes. These multivariate relationships often occurred only after adjustment for age, gender, body mass index, serum alkaline phosphatase activity, or tobacco use. We conclude that there are significant relationships between plasma vitamin levels and both components of CTS (specific symptoms and median nerve slowing). The interaction between plasma PLP and ASC appears to be particularly important with respect to symptoms.

Adult↗
PubMed1996

Tobacco, caffeine, alcohol, and carpal tunnel syndrome in American industry. A cross-sectional study of 1464 workers.

We investigated the effects of three legal drugs (tobacco, caffeine, and alcohol) on the prevalence of carpal tunnel syndrome (CTS) confirmed by nerve conduction studies (definite CTS) in two groups of American industrial workers: 656 nonclaimant workers and 808 working patients referred for upper extremity symptoms. Comparing workers with definite CTS to workers without definite CTS revealed 26% greater current use of tobacco, 19% greater lifetime use of tobacco, 5% greater current use of caffeine, 14% lesser current use of alcohol, and 75% greater history of alcohol abuse in the workers with definite CTS. All these differences were statistically significant. Those who currently used alcohol but not tobacco or caffeine were at the lowest risk for slowing, symptoms, and definite CTS. Those who currently used caffeine alone or in combination with tobacco were at the highest risk. In female workers, current smoking, current caffeine use, and current coffee consumption independently predicted 5.0% of the explainable risk for definite CTS. In male workers, history of alcohol abuse and current beer consumption independently predicted 3.0% of the explainable risk for definite CTS. Prevalence of slowing, symptoms, and definite CTS in 12 specific job categories correlated directly with current tobacco use. We conclude that the use of legal drugs affects the prevalence of median nerve slowing, symptoms, and carpal tunnel syndrome, but the effects of the drugs independently explain only a small portion of the total risk. Nevertheless, legal drug use or abuse may serve as a marker for increased CTS risk.

Adult↗
PubMed1994

Slowing of sensory conduction of the median nerve and carpal tunnel syndrome in Japanese and American industrial workers.

As part of a continuing study of the causes of carpal tunnel syndrome (CTS) in industry, we measured sensory conduction of the median nerve in 101 Japanese furniture factory workers. We used the maximum latency difference (MLD) with a critical value of > or = 0.40 msec to indicate abnormal slowing of nerve conduction. The prevalence of slowing in the Japanese workers was 17.8%, while the prevalence of probable CTS (based on symptoms only) was 2.5%, and the prevalence of definite CTS (probable CTS confirmed by slowing) was 2.0%. The most important factor predicting the MLD was the body mass index. The MLD was the most important factor predicting probable CTS. The prevalence of slowing in the Japanese workers was not significantly different from the prevalence of slowing in 316 American workers from four industries (22.0%), but the prevalences of probable CTS and definite CTS were much lower in the Japanese. The meaning of these findings is discussed.

Adolescent↗
PubMed1993

Predictive value of nerve conduction measurements at the carpal tunnel.

We compared the predictive values of three measurements of sensory conduction of the median nerve at the carpal tunnel (maximum latency difference [MLD], 8-cm latency [S8], and 14-cm latency [S14]) in 2334 hands of industrial workers, workers' compensation patients, and students. The MLD was determined by the centimetric technique. The MLD was the most sensitive and efficient measurement for predicting carpal tunnel syndrome (CTS). An MLD > or = 0.40 ms correctly identified 86.3% of 753 hands with CTS. The MLD correlated best with CTS and with the primary diagnostic category (CAT). MLD was the second factor selected in stepwise regression analysis for CAT (numbness was first and S8 was third). The MLD was the most important factor for predicting persistent or de novo CTS in a 5-year follow-up of 630 hands. Thus, the MLD was the most reliable nerve conduction study measurement for predicting current or future CTS in these subjects' hands.

Adult↗
PubMed1993

Validation of occupational hand use categories.

As part of a study of the etiology of carpal tunnel syndrome in industry, we developed a measure of occupational hand use activities, "Occupational Hand Use" (OHU), using 471 workers from four industries. This categorization has five categories based primarily upon observed relative force and secondarily upon observed relative repetitions. Because the validity of this OHU categorization has been questioned, we devised a study to validate this variable by demonstrating its reliability. Using discriminant analysis, we show that the OHU categorization accurately reflects the subjective impressions of other industrial workers (605 workers from four other industries in the United States and Japan). Within each validation industry, 68 to 88% of all workers were classified precisely to the correct OHU category, and an additional 10 to 25% were classified to within one OHU category, for a hit or near-miss rate of 87 to 98%. The major classification error was due to some workers overestimating the repetitiousness of their jobs. An equation for calculating OHU from subjective or objective data is provided.

Adult↗
PubMed1977

The United States drug problem and international trafficking. Part II. Denial of safe-havens to illicit drug traffickers.

Excessive reliance on extradition as a means of acquiring prosecutional control over illicit drug traffickers is short-sighted. Informal arrangements, like expulsion, should be given more consideration. A method for developing a unified antitrafficker policy and for implementing that policy through existing diplomatic channels is demonstrated through the use of the safe-haven deprivation/deterrence model. This paper focuses on drug traffickers. Trafficking is a function of the availability of both suppliers and consumers. Other available forms of cooperation within the United States government to induce foreign states to assure that opium crops are either destroyed or controlled within licit user channels should not be overlooked.

Drug and Narcotic Control↗