Can sensation of cold hands predict Raynaud's phenomenon or paraesthesia?

Background: Raynaud's phenomenon and neurosensory symptoms are common after hand-arm vibration exposure. Knowledge of early signs of vibration injuries is needed. Aims: To investigate the risk of developing Raynaud's phenomenon and paraesthesia in relation to sensation of cold hands in a cohort of male employees at an engineering plant. Methods: We followed a cohort of male manual and office workers at an engineering plant in Sweden for 21 years. At baseline (1987 and 1992) and each follow-up (1992, 1997, 2002, 2008), we assessed sensation of cold, Raynaud's phenomenon and paraesthesia in the hands using questionnaires and measured vibration exposure. We calculated risk estimates with univariate and multiple logistic regression analyses and adjusted for vibration exposure and tobacco usage. Results: There were 241 study participants. During the study period, 21 individuals developed Raynaud's phenomenon and 43 developed paraesthesia. When adjusting the risk of developing Raynaud's phenomenon for vibration exposure and tobacco use, the odds ratios were between 6.0 and 6.3 (95% CI 2.2-17.0). We observed no increased risk for paraesthesia in relation to a sensation of cold hands. Conclusions: A sensation of cold hands was a risk factor for Raynaud's phenomenon. At the individual level, reporting a sensation of cold hands did not appear to be useful information to predict future development of Raynaud's phenomenon given a weak to moderate predictive value. For paraesthesia, the sensation of cold was not a risk factor and there was no predictive value at the individual level.

Seated postural neck and trunk reactions to sideways perturbations with or without a cognitive task.

Driving on irregular terrain will expose the driver to sideways mechanical shocks or perturbations that may cause musculoskeletal problems. How a cognitive task, imposed on the driver, affects seated postural reactions during perturbations is unknown. The aim of the present study was to investigate seated postural reactions in the neck and trunk among healthy adults exposed to sideways perturbations with or without a cognitive task. Twenty-three healthy male subjects aged 19-36 years, were seated on a chair mounted on a motion system and randomly exposed to 20 sideways perturbations (at two peak accelerations 5.1 or 13.2m/s(2)) in two conditions: counting backwards or not. Kinematics were recorded for upper body segments using inertial measurement units attached to the body and electromyography (EMG) was recorded for four muscles bilaterally in the neck and trunk. Angular displacements (head, neck, trunk and pelvis) in the frontal plane, and EMG amplitude (normalised to maximum voluntary contractions, MVC) were analysed. The cognitive task provoked significantly larger angular displacements of the head, neck and trunk and significantly increased EMG mean amplitudes in the upper neck during deceleration, although 10% of MVC was never exceeded. A cognitive task seems to affect musculoskeletal reactions when exposed to sideways perturbations in a seated position.

Neck pain combined with arm pain among professional drivers of forest machines and the association with whole-body vibration exposure.

The purpose of this study was to investigate the existence of neck pain and arm pain among professional forest machine drivers and to find out if pain were related to their whole-body vibration (WBV) exposure. A self-administered questionnaire was sent to 529 forest machine drivers in northern Sweden and the response was 63%. Two pain groups were formed; 1) neck pain; 2) neck pain combined with arm pain. From WBV exposure data (recent measurements made according to ISO 2631-1, available information from reports) and from the self-administered questionnaire, 14 various WBV exposure/dose measures were calculated for each driver. The prevalence of neck pain reported both for the previous 12 months and for the previous 7 d was 34% and more than half of them reported neck pain combined with pain in one or both arms. Analysis showed no significant association between neck pain and high WBV exposure; however, cases with neck pain more often experienced shocks and jolts in the vehicle as uncomfortable. There was no significant association between the 14 WBV measures and type of neck pain (neck pain vs. neck pain combined with arm pain). It seems as if characteristics of WBV exposure can explain neither existence nor the type of neck pain amongst professional drivers of forest machines. The logging industry is important for several industrialised countries. Drivers of forest machines frequently report neuromusculoskeletal pain from the neck. The type of neck pain is important for the decision of treatment modality and may be associated with exposure characteristics at work.

Fifty-year follow-up of mortality among a cohort of iron-ore miners in Sweden, with specific reference to myocardial infarction mortality.

OBJECTIVES: This study investigates both general mortality and mortality from myocardial infarction among men employed in iron-ore mines in Sweden. METHODS: The mortality of employees (surface and underground workers) at the iron-ore mines in Malmberget and Kiruna, Sweden was investigated. The study cohort comprised men who had been employed for at least 1 year between 1923 and 1996. The causes of death were obtained from the national cause of death register from 1952 to 2001. Indirect standardised mortality ratios (SMR) were calculated for four main causes. Mortality specifically from myocardial infarction was also analysed. RESULTS: 4504 deaths in the cohort gave an SMR for total mortality of 1.05 (95% CI 1.02 to 1.09). Mortality was significantly higher for lung cancer (SMR 1.73, 95% CI 1.52 to 1.97). There was an increased risk of injuries and poisonings (SMR 1.34, 95% CI 1.24 to 1.46) and respiratory diseases (SMR 1.14, 95% CI 1.00 to 1.28). There were 1477 cases of myocardial infarction, resulting in an SMR of 1.12 (95% CI 1.07 to 1.18). SMR was higher (1.35, 95% CI 1.22 to 1.50) for men aged 60 years of age (1.06, 95% CI 1.00 to 1.13). CONCLUSIONS: Mortality from myocardial infarction was higher than expected. There was also an increased risk of death from injuries and poisonings, lung cancer and respiratory diseases, as well as higher general mortality. Our findings support the results of previous studies that there is an association between working in the mining industry and adverse health outcomes.

Thermal perception thresholds among young adults exposed to hand-transmitted vibration.

INTRODUCTION: Quantitative sensory testing assesses non-invasively the function of the sensory pathways from receptors to cortex. Studies of workers exposed to vibration support evidence that neuro-sensory hand-arm vibration syndrome also encompasses neuropathy of the small-diameter nerve fibres. OBJECTIVES: To assess the risk of disturbed thermal perception developing among young adults exposed to vibration and hand-intensive manual work. The aim also encompasses the study of alternative covariates in small-diameter nerve fibre neuropathy assessment. METHODS: This cross-sectional multi-centre study comprised 202 males and females from vocational school programs in auto mechanics, construction and catering. The testing included a baseline questionnaire, a clinical examination focusing on upper extremity disorders and quantitative somatosensory testing. Thermal perception thresholds were assessed, on both hands, second and fifth digits, using a modified Marstock method for warmth and cold. RESULTS: Reduced thermal perception sensitivity was found for digit II compared to digit V, for females compared to males, and between the two study centres. Subjects exposed to vibration at work showed reduced sensitivity to temperature compared to non-vibration exposed. In univariate analyses odds ratios of 1.06 (95% CI 1.006-1.118) and 1.02 (95% CI 0.971-1.078) for reduced perception to cold for the right and left hands, respectively, was found for vibration. This association was lost in multivariate analyses. The study centre was the strongest confounding influence. CONCLUSIONS: Sensitivity to temperature appears to be reduced despite the subjects short exposure-time and low exposure to vibration. The effect is small in relation to other confounding factors. A low agreement between the modalities indicates the need for separate tests for cold and warmth. Hand-side, age, stature, and BMI were not important for thermal perception but study centre, gender and choice of digit were. Conventional electro-diagnostic investigations are inadequate for evaluating the status of the small-fibre afferent systems leaving QST of thermal perception as the preferred diagnostic tool.

Relationship between vibration dose and the absorption of mechanical power in the hand.

OBJECTIVES: The aim of this study was to examine the relationship between calculated vibration dose and the measured absorption of vibration power in the human hand, as well as the measured grip and feed forces applied by the subjects. METHODS: The study was carried out with 10 healthy subjects. A special handle was used during the measurements. The influence of 4 different vibration levels with different durations during a test period of 5 minutes was investigated. The number of exposure intervals varied between 1 and 5. The same overall equivalent acceleration was used in all the experiments. RESULTS: There is a significant difference between the calculated vibration dose and the amount of measured absorption of power. A higher acceleration level leads to significantly higher absorption. Furthermore, the outcome shows that rest periods contribute to a lower absorption of power in the hand and also lower feed forces. Conclusions This study supports the hypothesis that vibration-free rest periods give the human organism an opportunity to recover.

Exposure-response relationship between hand-arm vibration and vibrotactile perception sensitivity.

BACKGROUND: The objectives of the study were to examine whether occupational use of vibrating hand-held tools was associated with an impaired vibrotactile perception, whether any exposure-response relationship exists, and whether the different populations of mechano-receptive afferent units are equally affected. METHODS: Vibrotactile perception thresholds have been measured at seven frequencies (8-500 Hz) and evaluated among 125 vibration-exposed and 45 non-exposed male employees in a heavy engineering production workshop. Vibration exposure measurements were assessed on tools in accordance with ISO 5349. Vibrotactile perception thresholds have been individually graded in stages and placed in relation to individual vibration exposure. RESULTS: The outcome did not reveal a clear relationship between vibration exposure and reduced vibrotactile sensitivity on an individual basis. There was a clear tendency on a group basis towards elevated thresholds when the study population was divided into three exposure categories. A fourfold increase in relative risk of reduced vibrotactile sensitivity for test frequencies above 40 Hz was observed between the highest exposure category compared to the non-exposed. CONCLUSIONS: It was concluded that reduced tactile sensitivity is related to the degree of vibration exposure but it is not at present possible to delineate an exposure-response relationship.

The influence of biodynamic factors on the mechanical impedance of the hand and arm.

The purpose of this study was to investigate the mechanical impedance of the human hand-arm system during exposure to random vibration under various experimental conditions and to evaluate statistically whether these experimental conditions have any influence on magnitude and phase of the mechanical impedance. A further aim was to compare the obtained results with other investigations where sinusoidal excitation has been used. The mechanical impedance was estimated in ten healthy subjects during exposure to random vibration, with a constant velocity spectrum within the frequency range 4-2000 Hz, by use of a specially designed laboratory handle. In the study, the influence of various conditions, such as vibration direction (Xh, Yh, Zh), grip force (25-75 N), feed force (20-60 N), frequency-weighted acceleration level (3, 6, 9, 12 m/s2) and hand and arm posture (five flexions, two abductions) were studied. The outcome showed that the vibration direction and the frequency of the vibration stimuli have a strong significant influence on the impedance of the hand. An increased vibration level resulted in a significantly lower impedance for frequencies over 100 Hz. Increase grip and feed forced led on the other hand to an increased impedance for all frequencies. With regard to hand and arm posture, the results show that the flexion and abduction had a significant contribution for frequencies below 30 Hz. Furthermore, the influence of some of the studied variables had a non-linear effect on the impedance but also differed between different exposure directions. It was concluded, moreover, that the vibration response characteristics of the hand and arm differ, depending whether the signal is a discrete frequency signal or a signal consisting of several frequencies.

Transmission of vibration energy to different parts of the human hand-arm system.

The aim of this study was to investigate the transmission of vibration energy to three selected points along the hand and arm (knuckle, wrist and elbow) and to compare the energy transmission for two different kinds of vibration exposures, i.e. random and sinusoidal. The transmission of vibration energy was estimated for ten subjects during exposure to random (within the frequency range 20-5000 Hz) and sinusoidal vibration at eight different frequencies (20, 40, 80, 160, 320, 630, 1250 and 1600 Hz). The random and sinusoidal vibrations had a frequency-weighted acceleration level of 3 m/s2. The energy transmission was determined by simultaneous vibration measurements at the vibrating handle and in the hand-arm system. The measurements were made with a laser-velocity transducer and specially constructed equipment. The grip and feed forces were held constant at 40 N. The results show that the energy transmission decreases with the distance from the source. The results also show that the energy transmission is dependent on the frequency for the random vibration exposures. No clear frequency dependence of the energy transmission could be found for the sinusoidal vibrations. It may also be concluded that there are differences in the energy transmission due to types of exposure, sinusoidal vibration showing higher transmission of energy to the hand-arm system than random vibration, especially at higher frequencies.

The influence of individual factors on the absorption of vibration energy in the hand and arm.

The detrimental effects of vibrating hand-held tools upon humans have been known for a long time, and determination of the absorption of vibration energy into the operator's hand and arm could be an alternative method of risk assessment. The energy absorption in the hand and arm during exposure to random vibration has been measured in 84 subjects, 40 males and 44 females. A special handle was used during the measurements. The influence of various experimental conditions, such as vibration level (3-12m/s2), vibration direction (Xh, Yh, Zh), and grip force (25-75 N) were studied. Furthermore, the influence on the absorption of different individual biological factors, such as age, weight, height, hand and arm dimensions as well as blood pressure were also investigated. The subject also provided demographic data through a questionnaire covering work, symptoms of finger blanching and numbness as well as current use of nicotine (snuff of tobacco). The results show that energy absorption is influenced by exposure directions and levels as well as grip forces. Furthermore, the results show that individual biological differences between subjects, for instance age, hand volume and hand thickness, have a significant influence on the amount of absorbed energy. Blood pressure had no influence on the absorption. The same was also found for the subjective reported symptoms of finger blanching or numbness as well as for use of nicotine.

Comparison of different methods for vibration measurements on hand-held vibrating tools.

Vibration measurements have been done on hand-held tools in a group of 48 platers by evaluating the individual vibration acceleration and absorption of vibration energy. The measurement of acceleration has been done frequency-weighted and frequency-unweighted in accordance with ISO 5349 and NIOSH (USA) recommendations for hand-arm vibration standards, respectively. The acceleration and the energy absorption have been measured simultaneously in the three orthogonal directions, the latter by using a specially designed adapter. The exposure time has been determined by both subjective rating and objective measurements. Individual energy-equivalent accelerations and vibration dosages have been calculated from these data. The outcome shows that the type of tool was critical to vibration load when the different measures for determining vibration levels were used. Of the methods used, the evaluation specified by ISO 5349 makes most consideration of low frequencies of vibration (< 50 Hz), absorption of vibration energy middle frequencies (50-200 Hz) and NIOSH of high frequencies (> 200 Hz). The results show a poor correlation between the three methods used. Close agreement between mean subjective rating and objective measurement of the average exposure time was found. Further studies of the relation between results presented here and generated disturbance will be conducted, which may clarify any exposure-response relationship.

Vibrotactile perception sensitivity and its relation to hand-arm vibration exposure.

Vibrotactile perception thresholds (VPT) at seven test frequencies (8-500 Hz) have been measured and evaluated among 170 male employees at a heavy engineering production workshop, 125 of them were at present, or in the past, exposed to hand-arm vibration. All participants were examined by a physician and none had symptoms of diseases or were exposed to other factors known to cause sensory neuropathies. VPTs [for the three lowest (8-32 Hz; non-Pacinian), for the four highest (63-500 Hz; Pacinian) and for all test frequencies together] and a sensitivity index (SI) has been individually graded in four (normal, slightly deteriorated, deteriorated and seriously deteriorated) and two (normal, abnormal) stages, respectively, and put in relation to individual exposure of vibration. The results do not show any clear relationship on an individual basis between vibration exposure and degraded vibrotactile perception. On a group basis, however, there is a clear tendency towards detoriorated VPTs when the study group is divided in exposure categories. The detorioration is most pronounced in the frequency range mediated by Pacinian corpuscles. In this range an approximately four-fold increase of relative risk for elevated VPT for those in the highest exposure category was observed compared to the non-exposed group. Corresponding relative risk estimate for SI is about 6. Therefore, the results suggest an existence of an exposure-response relationship.

Assessment of heat pain perception in relation to vibration exposure.

The effect of vibration on thin unmyelinated sensory fibers was studied by perception threshold measurement of heat pain. The investigation was a cross-sectional study of 98 vibration-exposed and 53 non-vibration-exposed workers. Pain perception was determined by using the "Marstock" method. The perception threshold of contact heat induced pain was assessed by the method of limits. Quantified personal energy-equivalent vibration exposure was assessed for all subjects on a group basis. The cumulated lifetime equivalent frequency-weighted vibration exposure was estimated based on measurements according to ISO 5349. The mean heat perception threshold was 46.2 degrees C (SD 2.6 degrees C) for the right hand and 46.0 degrees C (SD 2.7 degrees C) for the left. The results showed no mean difference (left = 0.1 degree C, right = 0.6 degree C) in heat pain perception between vibration-exposed and non-exposed subjects. There was a high correlation between the right and left hand measurements (r = 0.81). The risk (rate ratio) for impairment was 1.02 (95% CI 0.81-1.30) for the right hand and 1.00 (95% CI 0.79-1.26) for the left. The results of the study did not indicate any impairment as assessed by an increased perception threshold for heat pain. The lack of an increased heat pain threshold among the vibration-exposed workers in our study cannot exclude a possible lesional somatosensory influence from the exposure, as the lesional effect may also be a lowering of the threshold. The multiple and unrelated percepts of thermal sensations imply that it is not legitimate to draw conclusions about the total status of the small calibre afferents when testing only the heat pain perception.

The influence of biodynamic factors on the absorption of vibration energy in the human hand and arm.

A possible basis for risk assessment for hand-transmitted vibration may be to determine the quantity of energy absorbed in the human hand and arm. In the present study the mechanical energy absorption in the hand-arm system has been measured on 10 healthy subjects during exposure to random vibration with constant velocity spectrum. In the study, the influence of various conditions, such as vibration direction (Xh, Yh, Zh), grip force (25-75 N), feed force (20-60 N), frequency weighted acceleration level (3, 6, 9, 12 m/s2) and hand and arm posture (5 flexions, 2 abductions) were studied. The outcome showed that the energy absorption in the human hand and arm depended mainly on the frequency and direction of the vibration stimuli. Higher vibration levels, as well as firmer hand grips and higher feed forces, resulted in a significantly higher absorption. As concerns the hand and arm posture the results show that the flexion had a significant contribution to the vibration absorption but the abduction had no influence on the quantity of absorbed energy. Furthermore, the influence of some of the studied variables had a non-linear effect on the absorption but also differed between different exposure directions. Moreover, it was concluded that the frequency-weighting routine in the international standard ISO 5349 do not reflect the energy absorbing properties of the human hand and arm.

Impaired nerve conduction in the carpal tunnel of platers and truck assemblers exposed to hand-arm vibration.

OBJECTIVES: The goal of this study was to assess the relative risks of sustaining impaired nerve conduction in the hands among vibration-exposed persons as opposed to nonvibration-exposed referents. METHODS: In a cross-sectional study design platers and truck assembly workers were contrasted to office workers. The 4-h frequency-weighted vibration was 4.6 m.s-2 and 1.0 m.s-2 for the platers and assemblers, respectively. The ergonomic factors were measured as forced grip time. The conduction velocity, distal latency time, and amplitude of the median nerve were measured for both hands. RESULTS: The sensory nerve conduction velocity was slower in the right hand than in the left. An increased risk of prolonged latency time was found for the platers and assemblers when contrasted to the office workers. The relative risks (rate ratios) of impaired nerve conduction for the carpal tunnel segment varied between 1.4 and 2.0 for the distal latency and between 0.9 and 1.7 for the nerve conduction velocity. The rate ratios were generally higher for the left-hand side than for the right-hand side. The risks were not proportional to either the weighted or unweighted vibration exposure. CONCLUSIONS: The contributions from vibration and ergonomic factors to impaired nerve conduction velocity were inseparable in this study. Ergonomic factors such as forceful gripping and extreme positions, apart from vibration exposure, may be strong determinants of impaired nerve conduction in the carpal tunnel area.

Absorption of vibration energy in the human hand and arm.

A possible basis for the risk assessment for hand-transmitted vibration may be to determine the amount of energy absorbed in the human hand and arm. In the present study, the mechanical energy absorption in the hand-arm system was measured within the frequency range of 4 to 1000 Hz. The study was carried out on ten healthy subjects during exposure to sinusoidal vibration. The influence of various experimental conditions, such as vibration direction (Xh, Yh, Zh), grip force (25-75 N), vibration level (8-45 mm/srms), and hand-arm posture were studied. The outcome shows that the energy absorption in the human hand and arm depended mainly on the frequency and direction of the vibration stimulus. Higher vibration levels, as well as firmer handgrips, resulted in higher absorption of energy. Varying hand-arm postures had only a small influence on the amount of absorbed energy, while the constitution of the hand and arm affected the energy absorption to a larger extent.

Perceptions of caring behaviors and patient anxiety and depression in cancer patient-staff dyads.

Cancer patient and staff perceptions of the importance of caring behaviors (Caring Assessment Instrument, CARE-Q) and patient levels of anxiety and depression (Hospital Anxiety and Depression Scale, HADS) were determined in 19 matched patient-staff dyads. Both groups perceived comforting and anticipating behaviors to be among the most important ones. Patients considered behaviors focused on staff explaining and facilitating to be more important than did staff, whereas staff rated behaviors concerning accessibility as more important than did patients. Patient and staff perceptions of the importance of comforting behaviors were negatively associated. No significant mean value difference or correlation was found on the HADS anxiety or depression subscales. Members of matched patient-staff dyads did not agree strongly on the importance of caring behaviors and patient levels of anxiety and depression.

Outcome of the abduction external rotation test among manual and office workers.

Reactions during the Abduction External Rotation (AER) test were studied among 71 platers and 70 assemblers exposed to vibratory tools and manual work and 45 unexposed white collar workers. The frequency of positive neurological reactions was 31% among the platers, 6% among the assemblers, and 16% among the white collar workers. Platers reported the highest fatigue rates in the shoulder regions during the test. A positive association was noted between a pathological AER test and current problems in the neck/scapula or shoulder/upper arm regions, day- or night-time numbness in the hands, tension neck, and carpal tunnel syndrome. Age, length of daily vibration exposure, and vibration acceleration level were also positively associated with a positive AER test outcome. The results indicate that the outcome of the AER test is sensitive to neck and shoulder disorders but also, to some extent, to the carpal tunnel syndrome.

Measurements of the impedance of the hand and arm.

The mechanical impedance of the hand and arm was studied on ten healthy subjects during exposure to sinusoidal vibration within the frequency range of 2 to 1000 Hz. A special handle for the measurements was constructed. The influence of vibration direction, handle grip, grip force, vibration level, hand-arm posture and sex as well as anthropometric data were studied. The results show that the impedance of the hand-arm mainly depends on the frequency and direction of the vibration stimuli. Higher vibration levels, as well as more firm hand-grips, resulted in higher impedance. Furthermore, the outcome shows that experiments conducted with different hand-arm postures had an active influence on the mechanical impedance. Moreover, the subjects' sex and constitution of the hand and arm affected the impedance to a large extent.