Aaron Thompson

Baseline repeated measures from controlled human exposure studies: associations between ambient air pollution exposure and the systemic inflammatory biomarkers IL-6 and fibrinogen.

Introduction Systemic inflammation may be one of the mechanisms mediating the association between ambient air pollution and cardiovascular morbidity and mortality. Interleukin-6 (IL-6) and fibrinogen are biomarkers of systemic inflammation that are independent risk factors for cardiovascular disease. Objective We investigated the association between ambient air pollution and systemic inflammation using baseline measurements of IL-6 and fibrinogen from controlled human exposure studies. Methods In this retrospective analysis we used repeated-measures data in 45 nonsmoking subjects. Hourly and daily moving averages were calculated for ozone, nitrogen dioxide, sulfur dioxide, and particulate matter ≤ 2.5 μm in aerodynamic diameter (PM2.5). Linear mixed-model regression determined the effects of the pollutants on systemic IL-6 and fibrinogen. Effect modification by season was considered. Results We observed a positive association between IL-6 and O3 [0.31 SD per O3 interquartile range (IQR); 95% confidence interval (CI), 0.08–0.54] and between IL-6 and SO2 (0.25 SD per SO2 IQR; 95% CI, 0.06–0.43). We observed the strongest effects using 4-day moving averages. Responses to pollutants varied by season and tended to be higher in the summer, particularly for O3 and PM2.5. Fibrinogen was not associated with pollution. Conclusions This study demonstrates a significant association between ambient pollutant levels and baseline levels of systemic IL-6. These findings have potential implications for controlled human exposure studies. Future research should consider whether ambient pollution exposure before chamber exposure modifies IL-6 response.

The sensitivity and specificity of thermometry and plethysmography in the assessment of hand-arm vibration syndrome

BACKGROUND Finger plethysmography and thermometry are objective measures used to assess the vascular aspect of hand-arm vibration syndrome (HAVS). Research to date shows poor correlation between these tests and Stockholm Workshop Scale (SWS) vascular stage. Clinicians, researchers and compensation boards require objective means to diagnose and quantify HAVS. AIMS To define the specificity and sensitivity of thermometry and plethysmography using the SWS as the reference criterion. A secondary goal was to consider cut points for the tests optimizing sensitivity and specificity. METHODS A cross-sectional analysis was conducted on HAVS patients seen at an occupational medicine specialty clinic. Plethysmography and thermometry were analyzed using SWS vascular stage as the outcome variable. Logistic regression controlled for age, smoking and time since last vibration exposure and use of vasoactive medications. The sensitivity and specificity of the combined tests were calculated using varying cut points. RESULTS A total of 139 patients consented to participate in the study. Plethysmography stage 1 or greater showed the highest sensitivity (sensitivity 94% and specificity 15%). Specificity was optimized combining plethysmography stage 3 and thermometry stage 3 (specificity 98% and sensitivity 23%). Maximal diagnostic accuracy was achieved by plethysmography alone setting the criteria for a positive test as being stage 1 or greater (70%). CONCLUSIONS Neither plethysmography nor thermometry either alone or in combination demonstrated sufficient sensitivity and specificity to serve as an objective correlate for SWS vascular stage. All combinations of plethysmography and thermometry showed a lower specificity than sensitivity indicating that the SWS may be less sensitive in detecting vascular pathology than the objective tests.

Vasospasm in the feet in workers assessed for HAVS

BACKGROUND Previous studies have suggested that the presence of the vascular component of hand-arm vibration syndrome (HAVS) in the hands increases the risk of cold-induced vasospasm in the feet. AIMS To determine if objectively measured cold-induced vasospasm in the hands is a risk factor for objectively measured cold-induced vasospasm in the feet in workers being assessed for HAVS. METHODS The subjects were 191 male construction workers who had a standardized assessment for HAVS including cold provocation digital photocell plethysmography of the hands and feet to measure cold-induced vasospasm. Bivariate analysis and multinomial logistic regression were used to examine the association between plethysmographic findings in the feet and predictor variables including years worked in construction, occupation, current smoking, cold intolerance in the feet, the Stockholm vascular stage and plethysmographic findings in the hands. RESULTS Sixty-one (32%) subjects had non-severe vasospasm and 59 (31%) had severe vasospasm in the right foot with the corresponding values being 57(30%) and 62 (32%) in the left foot. Multinomial logistic regression indicated that the only statistically significant predictor of severe vasospasm in the feet was the presence of severe vasospasm in the hands (OR: 4.11, 95% CI: 1.60-10.6, P < 0.01 on the right side and OR: 4.97, 95% CI: 1.82-13.53, P < 0.01 on the left side). Multinomial logistic regression analysis did not indicate any statistically significant predictors of non-severe vasospasm in the feet. CONCLUSIONS Workers assessed for HAVS frequently have cold-induced vasospasm of their feet. The main predictor of severe vasospastic foot abnormalities is severe cold-induced vasospasm in the hands.

Vibration induced white-feet: Overview and field study of vibration exposure and reported symptoms in workers

BACKGROUND Workers who stand on platforms or equipment that vibrate are exposed to foot-transmitted vibration (FTV). Exposure to FTV can lead to vibration white feet/toes resulting in blanching of the toes, and tingling and numbness in the feet and toes. OBJECTIVES The objectives are 1) to review the current state of knowledge of the health risks associated with foot-transmitted vibration (FTV), and 2) to identify the characteristics of FTV and discuss the associated risk of vibration-induced injury. PARTICIPANTS Workers who operated locomotives (n=3), bolting platforms (n=10), jumbo drills (n=7), raise drilling platforms (n=4), and crushers (n=3), participated. METHODS A tri-axial accelerometer was used to measure FTV in accordance with ISO 2631-1 guidelines. Frequency-weighted root-mean-square acceleration and the dominant frequency are reported. Participants were also asked to report pain/ache/discomfort in the hands and/or feet. RESULTS Reports of pain/discomfort/ache were highest in raise platform workers and jumbo drill operators who were exposed to FTV in the 40 Hz and 28 Hz range respectively. Reports of discomfort/ache/pain were lowest in the locomotive and crusher operators who were exposed to FTV below 10 Hz. These findings are consistent with animal studies that have shown vascular and neural damage in exposed appendages occurs at frequencies above 40 Hz. CONCLUSIONS Operators exposed to FTV at 40 Hz appear to be at greater risk of experiencing vibration induced injury. Future research is required to document the characteristics of FTV and epidemiological evidence is required to link exposure with injury.

Health-care barriers for workers with HAVS in Ontario, Canada

BACKGROUND Hand-arm vibration syndrome (HAVS) becomes irreversible unless it is identified early and progression prevented. AIMS To describe the health-care-seeking behaviours of workers with HAVS and barriers to health care. METHODS We invited all patients assessed for HAVS between 15 January and 27 March 2013 at a hospital-based occupational health clinic (OHC) in Ontario, Canada, to complete a questionnaire asking why and from whom they sought health care, reasons they waited to seek care and barriers they encountered in accessing care. We analysed the data using descriptive statistics. RESULTS Forty-one (82%) patients agreed to participate. Thirty-seven had confirmed HAVS; 30 (84%) were Stockholm workshop vascular stage 2 or greater and 35 (97%) were sensorineural stage 1 or greater. The commonest employment sectors were construction [21 (57%)] and mining [6 (17%)]. The main reasons for seeking treatment were pain [11 (30%)], finger numbness [8 (22%)] and functional limitations [5 (14%)]. The commonest initial point of health care was the family physician [23 (66%)]. The mean wait between symptom onset and seeking treatment was 3.4 years, while the mean time between onset and OHC assessment was 9 years. Reasons for delay in seeking care were ignorance of the seriousness and irreversibility of HAVS and ability to continue to work. Family physicians suspected HAVS in 17% of cases and recommended job modification in 34%. CONCLUSIONS Workers with HAVS in Ontario delay seeking health care. Primary care physicians often fail to recognize HAVS. Barriers to health care include ignorance of HAVS and of the importance of prevention.

Hand-arm vibration syndrome: Workers' experience with functional impairment and disability

STUDY DESIGN Qualitative and descriptive study. INTRODUCTION Hand-arm vibration syndrome (HAVS) is a prevalent disease in Canada. There is little work on the perspectives of HAVS patients. PURPOSE OF THE STUDY Explore perceptions of disability and functional compromise in patients with HAVS. METHODS Semi-structured telephone interviews were conducted with HAVS patients and analysed using content analysis. RESULTS The 11 participants reported numbness, pain, and reduced dexterity, strength, and sensation. Participants noted that HAVS was an inevitable aspect of their work. They indicated frustration with their condition and viewed it as a disability. To overcome impairments risky strategies are often used. Participants reported lack of support to manage symptoms and overcome work disability. DISCUSSION HAVS related impairment is disabling. Workers require improved resources and support to address symptom management and safe strategies to minimize work disability. CONCLUSION HAVS patients experience functional, social, emotional, and psychological disability. LEVEL OF EVIDENCE Not applicable.

B-vitamin Supplementation Mitigates Effects of Fine Particles on Cardiac Autonomic Dysfunction and Inflammation: A Pilot Human Intervention Trial

Ambient fine particle (PM2.5) pollution triggers acute cardiovascular events. Individual-level preventions are proposed to complement regulation in reducing the global burden of PM2.5–induced cardiovascular diseases. We determine whether B vitamin supplementation mitigates PM2.5 effects on cardiac autonomic dysfunction and inflammation in a single-blind placebo-controlled crossover pilot trial. Ten healthy adults received two-hour controlled-exposure-experiment to sham under placebo, PM2.5 (250 μg/m3) under placebo, and PM2.5 (250 μg/m3) under B-vitamin supplementation (2.5 mg/d folic acid, 50 mg/d vitamin B6, and 1 mg/d vitamin B12), respectively. At pre-, post-, 24 h-post-exposure, we measured resting heart rate (HR) and heart rate variability (HRV) with electrocardiogram, and white blood cell (WBC) counts with hematology analyzer. Compared to sham, PM2.5 exposure increased HR (3.8 bpm, 95% CI: 0.3, 7.4; P = 0.04), total WBC count (11.5%, 95% CI: 0.3%, 24.0%; P = 0.04), lymphocyte count (12.9%, 95% CI: 4.4%, 22.1%; P = 0.005), and reduced low-frequency power (57.5%, 95% CI: 2.5%, 81.5%; P = 0.04). B-vitamin supplementation attenuated PM2.5 effect on HR by 150% (P = 0.003), low-frequency power by 90% (P = 0.01), total WBC count by 139% (P = 0.006), and lymphocyte count by 106% (P = 0.02). In healthy adults, two-hour PM2.5 exposure substantially increases HR, reduces HRV, and increases WBC. These effects are reduced by B vitamin supplementation.

Health and safety training and prevention of hand-arm vibration syndrome through education

BACKGROUND: Exposure to hand operated vibrating tools in the construction industry places workers at risk for developing hand-arm vibration syndrome (HAVS), which is a common occupational disease. OBJECTIVE: To outline health and safety training obtained by construction workers and to assess which factors influence anti-vibration (AV) glove utilization following an educational intervention provided during a clinical assessment for HAVS at an occupational health clinic. METHODS: One hundred participating workers from the construction industry referred for a HAVS assessment at a hospitalbased ambulatory occupational health clinic in Toronto, Ontario, Canada. A baseline and two-month follow-up questionnaire were completed. RESULTS: Almost all of the participants indicated that they had completed health and safety training within their workplace. However, few received training specific regarding HAVS or AV gloves. Participants’ AV glove use improved from 4.3% at baseline to 53.3% at follow-up two months later. Key predictors of participants wearing AV gloves was sharing the educational intervention information with their supervisors and working in a workplace with 20 or more employees. CONCLUSIONS: Training specific to HAVS and AV gloves is lacking in the construction industry. The educational intervention proved most effective in increasing AV glove use when the information was shared within the workplace.

Health care utilization characteristics in patch test patients.

BackgroundThe length of time between onset of symptoms and definitive diagnosis is associated with outcomes in contact dermatitis (CD). Understanding the health care experience of patients with CD could identify areas for improvement. ObjectiveThe objective of the study was to describe the health care experience of individuals being patch tested and the barriers and facilitators to their seeking care. MethodsOne hundred forty-nine patients completed a survey containing information on types of health care providers seen, length of wait times, and barriers and facilitators to seeking care. ResultsSixty-six percent were first assessed by their family physicians. Forty-five percent waited more than 3 months before seeing a health care provider. Common reasons for delay included thinking their symptoms (1) would get better, (2) were not serious enough, or (3) were not limiting their ability to work or carry out other activities. Most patients waited less than 3 months for dermatological assessment and for patch test consultation after referral. ConclusionsPatients with possible CD spend considerable time in the health care system before they undergo definitive assessment. Understanding the reasons for not seeking care may be useful for promoting earlier evaluation and intervention to result in better outcomes.

Practice patterns of occupational medicine physicians in Canada

ABSTRACT The objectives of this survey were to identify the practice patterns of Canadian physicians working in the field of occupational medicine and to determine whether the type of certification influences the nature of the work they perform in the field. An Internet-based survey was conducted in September 2015 of members of the Occupational and Environmental Medicine Association of Canada. Eighty-six Canadian-based occupational medicine physicians completed the survey (response rate 36%). These physicians performed a wide variety of tasks (12 ± 6), with few spending most of their time doing a single task. The most frequently performed tasks were fitness-to-work (78%) and return-to-work evaluations (78%). Specialty-trained physicians were more likely to be involved in teaching and research and less likely to be involved in a variety of ability-to-work evaluations.