Tremor measurements in a 22-year cohort study of workers exposed to hand-held vibrating tools.

OBJECTIVES: The objectives of this cohort study were to evaluate possible long-term effects of occupational exposure to hand-arm vibration (HAV) in terms of increased tremor. The aims were to evaluate whether exposure during follow-up, baseline hand-arm vibration syndrome (HAVS), baseline manual dexterity or current medical conditions or life-style habits might be associated with increased tremor. A further aim was to compare two different activation conditions: postural vs rest tremor. METHODS: Forty men (current age: 60.4 years) who had previously worked as manual workers in a specialized engineering and construction company enrolled in the study. Their hand functions had been examined in 1994. At the baseline examination, 27 had been diagnosed with HAVS, while 13 were not exposed. The follow-up examination in 2016-2017 comprised the CATSYS Tremor Pen® for measuring postural and rest tremor and the Grooved Pegboard Test for assessing manual dexterity. Blood samples were taken for assessing biomarkers that might have impact on tremor. RESULTS: Neither cumulative exposure to HAV during follow-up nor HAVS at baseline were associated with increased tremor. A test for manual dexterity at baseline was significantly associated with increased tremor (Tremor Intensity) at follow-up. Blood markers of current medical conditions and tobacco consumption were associated with increased tremor. Rest tremor frequency was higher than postural tremor frequency (p < 0.001). CONCLUSIONS: The main findings of this 22-year cohort study were no indications of long-term effects on tremor related to HAV exposure and previous HAVS status. However, baseline manual dexterity was significantly associated with increased tremor at follow-up. Activation conditions (e.g., hand position) are important when testing tremor.

Inorganic chloramines: a critical review of the toxicological and epidemiological evidence as a basis for occupational exposure limit setting.

Inorganic chloramines are not commercially available, but monochloramine is produced in situ for disinfection or for use in chemical synthesis. Inorganic chloramines are also formed when free chlorine reacts with nitrogen containing substances, e.g. ammonia and urea, present in chlorinated water sources. Occupational exposure may, therefore, occur in e.g. swimming pool facilities and the food processing industry. Monochloramine is soluble and stable in water and the dominating inorganic chloramine in chlorinated water sources. No clinical effects were seen in healthy volunteers given monochloramine in drinking water during 4 or 12 weeks in doses of 0.043 or 0.034 mg/kg bw/day, respectively. Limited data indicate that monochloramine is weakly mutagenic in vitro but not genotoxic in vivo. One drinking water study indicated equivocal evidence of carcinogenicity in female rats but not in male rats and mice. No reproductive or developmental effects were shown in rodents in the few studies located. Dichloramine is soluble but unstable in water. In the only study located, mild histological effects in kidneys, thyroid and gastric cardia were observed in rats administered dichloramine in drinking water for 13 weeks. Trichloramine is immiscible with water and evaporates easily from water into air. Therefore, the primary exposure route of concern in the occupational setting is inhalation. Occupational exposure to trichloramine has been demonstrated in indoor swimming pool facilities and in the food processing industry where chlorinated water is used for disinfection. Exposure-response relationships between airborne levels and self-reported ocular and upper airway irritation have been shown in several studies. Exposure to trichloramine may aggravate asthma symptoms in individuals with existing asthma. The risk of developing asthma following long-term exposure to trichloramine cannot be evaluated at present. No data on genotoxic, carcinogenic, reproductive or developmental effects were located. The toxicological data for mono- and dichloramine are insufficient to recommend health-based occupational exposure limits (OELs).As regard trichloramine, the critical effect is judged to be irritation observed in several studies on pool workers, starting at approximately 0.4 mg/m3 (stationary sampling). Based on these data, a health-based OEL of 0.1 mg/m3 (8-h time-weighted average) is recommended. This corresponds to 0.2 mg/m3 for stationary measurements in swimming pool facilities. No short-term exposure limit (STEL) is recommended.

Longitudinal associations between cardiorespiratory fitness and stress-related exhaustion, depression, anxiety and sleep disturbances.

BACKGROUND: In the last few years, so-called "common mental disorders", including adjustment disorder and stress-related exhaustion, have outrivalled musculoskeletal disorders as being the leading cause of long-term sick leave in Sweden. Cardiorespiratory fitness level defined as "the maximal amount of physiological work that an individual can do as measured by oxygen consumption" has in many studies shown to reduce the risk of several life-style related diseases and moreover to improve mood, well-being and physical performance. The aim of the present study was to investigate, longitudinal associations between cardiorespiratory fitness and self-reported physical activity levels and the severity of symptoms connected to stress-related exhaustion, depression, anxiety, and sleep disturbances among women clinically diagnosed with stress-related exhaustion disorder (ED). METHODS: The study was that of a longitudinal cohort study consisting of women (n = 88) diagnosed with stress-related ED in a specialist clinic in Gothenburg, Sweden. Cardiorespiratory fitness was measured with the Åstrand indirect test of maximal oxygen uptake (VO2max) and subjective measures of physical activity levels were rated on 4-graded physical activity scale. To measure and follow symptoms of ED over time the SMBQ-questionnaire (Shirom Melamed Burnout Questionnaire) was used. The Hospital Anxiety and Depression Scale (HADS) was used to measure depression and anxiety. A proxy variable for capturing overall disturbed sleep used to measure sleep. Longitudinal associations for continuous outcome variables and the dichotomous variable sleep were analysed using mixed- effects regression models with random intercepts. Regression coefficients along with the 95% confidence interval (CI) are presented as measures of association. Both exposures and the outcome were measured simultaneously over six waves (T1-T6). RESULTS: The results showed statistically significant associations between level of fitness and reduced symptoms of stress-related exhaustion over time. Best improvements over time were seen in patients having a medium cardiorespiratory fitness level. No associations could be found between cardiorespiratory fitness level over time and anxiety, depression or sleep disturbances. CONCLUSION: Having medium cardiorespiratory fitness was positivity associated with a more sustained reduction in symptoms of ED overtime compared to those having low or high cardiorespiratory fitness levels. The clinical implication following this result is that an individual recommendation based on a medium level of physical activity in line with the recommendations from ACSM (American College of Sports Medicine) is preferable compared to recommendations including more vigorous physical activity in order to restore and sustainably reduce symptoms of exhaustion disorder over time.

Quantitatively measured tremor in hand-arm vibration-exposed workers.

OBJECTIVES: The aim of the present study was to investigate the possible increase in hand tremor in relation to hand-arm vibration (HAV) exposure in a cohort of exposed and unexposed workers. METHODS: Participants were 178 male workers with or without exposure to HAV. The study is cross-sectional regarding the outcome of tremor and has a longitudinal design with respect to exposure. The dose of HAV exposure was collected via questionnaires and measurements at several follow-ups. The CATSYS Tremor Pen(®) was used for measuring postural tremor. Multiple linear regression methods were used to analyze associations between different tremor variables and HAV exposure, along with predictor variables with biological relevance. RESULTS: There were no statistically significant associations between the different tremor variables and cumulative HAV or current exposure. Age was a statistically significant predictor of variation in tremor outcomes for three of the four tremor variables, whereas nicotine use was a statistically significant predictor of either left or right hand or both hands for all four tremor variables. CONCLUSIONS: In the present study, there was no evidence of an exposure-response association between HAV exposure and measured postural tremor. Increase in age and nicotine use appeared to be the strongest predictors of tremor.

Quantitative methods for evaluating the efficacy of thalamic deep brain stimulation in patients with essential tremor.

BACKGROUND: Deep brain stimulation (DBS) of the thalamus is a safe and efficient method for treatment of disabling tremor in patient with essential tremor (ET). However, successful tremor suppression after surgery requires careful selection of stimulus parameters. Our aim was to examine the possible use of certain quantitative methods for evaluating the efficacy of thalamic DBS in ET patients in clinical practice, and to compare these methods with traditional clinical tests. METHODS: We examined 22 patients using the Essential Tremor Rating Scale (ETRS) and quantitative assessment of tremor with the stimulator both activated and deactivated. We used an accelerometer (CATSYS tremor Pen) for quantitative measurement of postural tremor, and a eurythmokinesimeter (EKM) to evaluate kinetic tremor in a rapid pointing task. RESULTS: The efficacy of DBS on tremor suppression was prominent irrespective of the method used. The agreement between clinical rating of postural tremor and tremor intensity as measured by the CATSYS tremor pen was relatively high (rs = 0.74). The agreement between kinetic tremor as assessed by the ETRS and the main outcome variable from the EKM test was low (rs = 0.34). The lack of agreement indicates that the EKM test is not comparable with the clinical test. DISCUSSION: Quantitative methods, such as the CATSYS tremor pen, could be a useful complement to clinical tremor assessment in evaluating the efficacy of DBS in clinical practice. Future studies should evaluate the precision of these methods and long-term impact on tremor suppression, activities of daily living (ADL) function and quality of life.

Incidence of cutaneous melanoma in Western Sweden, 1970-2007.

The aim of this study was to describe the increasing incidence of cutaneous malignant melanoma (CMM) in Western Sweden during the period 1970-2007. A secondary aim was to show a geographical variation in incidence between coastal and inland areas, considering the effects of the local average duration of sunshine, and the sun exposure-related behavior in the populations. The Swedish Cancer Registry provided data on invasive melanomas during 1970-2007. Meteorological maps showed the annual average duration of sunshine during 1961-1990. A survey from 2007 with 2871 participants, carried out by the National Board of Health and Welfare, provided data on self-reported sun exposure. During the period studied, the age-standardized incidence for men in Western Sweden more than quadrupled to 31.1/100 000 inhabitants, whereas it tripled for women to 27.1/100 000. Coastal areas, including Gothenburg city, had a high average duration of sunshine (1701-1900 h of sun/year), whereas inland areas had lower average duration of sunshine (≤1700 h). The incidence of CMM was higher in coastal areas and in Gothenburg city, compared with inland areas. This may be linked to ultraviolet radiation, a consequence of the higher average duration of sunshine. The sun exposure survey showed additional factors, which possibly led to the increased incidence, for example high sun exposure on holidays abroad. The alarming increase in the incidence of CMM in Western Sweden, during the period 1970-2007, shows the need for additional primary preventive measures, for example sun protection programs targeted at populations in this area.

Neuromotor function in ship welders after cessation of manganese exposure.

PURPOSE: The aim of the present study was to investigate whether previous long-term exposure to manganese (Mn) via inhalation of welding fumes can cause persistent impairment in neuromotor function even long after cessation of exposure. METHODS: Quantitative tests of tremor, motor speed, manual dexterity, diadochokinesis, eye-hand coordination and postural stability were administered to 17 retired ship welders (mean age 69 years), with mean exposure time 28 years. The welders' exposure had ceased on average 18 years before the study. A cumulative exposure index (CEI) was calculated for each of the former welders. The welders were compared with 21 referents from the same shipyards (mean age was 66 years). RESULTS: Former welders performed less well than referents in the grooved pegboard test, and poorer performance was associated with CEI. The performance in most of the other neurobehavioral tests was similar between groups, but the welders tended to perform slightly better than the referents in tests demanding hand steadiness. The latter finding may be due to a training effect from their former working tasks or selection bias into or out of this occupation. CONCLUSIONS: In the present study of welders with previous welding fume exposure, former welders and referents performed similarly in most of the neurobehavioral tests. Previous adverse effects on the neuromotor system might have ceased, and decreased neuromotor function due to normal aging processes in both groups might have disguised any slight effect of previous Mn exposure. The poorer performance in the grooved pegboard test among welders may indicate an adverse effect on motor function of long-term exposure to Mn, but this finding has to be confirmed by other studies.

Quantitative assessment of neuromotor function in workers with current low exposure to mercury vapor.

Evaluation of neuromotor function has been used in several epidemiological studies of workers with long-term exposure to mercury vapor (Hg 0). Some recent studies indicate adverse effects at relatively low exposure levels. In the present study, we used sensitive quantitative methods, developed specifically to detect subtle effects of exposure to toxins on motor function. After exclusion of individuals with neurological diseases or other conditions that may affect performance, 43 chloralkali workers with current low exposure to Hg 0, and 22 age-matched referents remained for further analysis. The median urinary mercury concentration in exposed workers was 5.9 microg/g (range 1.3-25) creatinine (microg/gC), while that in referents was 0.7 microg/gC (range 0.2-4.1). The mean exposure time was 15 years, and the median cumulative mercury index was 161 years x microg/gC in exposed workers. A eurythmokinesimeter (EKM) was used to quantify eye-hand coordination, and a diadochokinesimeter, to measure rapid alternating rotation of the forearms. In general, the differences in performance between the exposed workers and the referents were small. Age was associated with a decrease in speed, more tremor, and longer contact duration between the stylus and the metal targets in performance of rapid pointing movements. Smokers had significantly more tremor, and more contacts per event in the EKM test, than nonsmokers. Taking age, shift work, and smoking habits into account, no significant associations with current or cumulative mercury exposure were found for the majority of the outcome variables from the quantitative tests. In general, this study indicates no significant adverse effects of Hg 0 on neuromotor function at the exposure levels studied.

Quantitative tremor assessment in workers with current low exposure to mercury vapor.

Measurement of tremor has been used in several occupational studies of workers with long-term exposure to mercury vapor (Hg(0)). Recent studies indicate an adverse effect even at relatively low exposure levels. In the present study, we used sensitive quantitative methods to assess tremor in chloralkali workers with current low exposure to Hg(0). Neurological examinations and recordings of tremor using both an accelerometer and a laser-based system were conducted in 43 mercury-exposed workers and 22 age-matched referents. The median urinary mercury concentration in exposed workers was 5.9 (1.3-25) microg/g creatinine (microg/gC), while it was 0.7 (0.2-4.1) microg/gC in referents. The mean exposure time was 15 years, and the median cumulative mercury index was 161 years x microg/gC in exposed workers. There were no differences between the exposed workers and the referents in the clinical evaluation of tremor. In the quantitative tremor tests, no associations were found with current or cumulative mercury exposure for the majority of tremor measures. There were indications that exposure to Hg(0) was associated with a lowering of tremor frequency in the non-dominant hand, and a possible interaction with smoking. The differences were small, however, and overall, this study indicates no significant adverse effects on tremor at these exposure levels.

Parkinson's disease in diphenyl-exposed workers--a causal association?

We report a cluster of five cases of Parkinson's disease (PD) among paper mill workers exposed to a fungicide, diphenyl. The cause of PD is still unknown, but epidemiological studies have indicated an elevated risk of developing PD after exposure to pesticides. The five cases of PD were found in a group of 255 diphenyl-exposed workers, and the number of expected cases in the exposed group was estimated to be 0.9, resulting in a relative risk of 5.6 (95% CI 1.8-13). Exposure to diphenyl may have contributed to this PD cluster, but chance is an alternative explanation.