Kurt T. Hegmann

The incidence of fibromyalgia and its associated comorbidities: a population-based retrospective cohort study based on International Classification of Diseases, 9th Revision codes.

Background:The epidemiology of fibromyalgia is poorly defined. The incidence of fibromyalgia has not been determined using a large population base. Previous studies based on prevalence data demonstrated that females are 7 times more likely to have fibromyalgia than males and that the peak age for females is during the childbearing years. Objective:We have calculated the incidence rate of fibromyalgia in a large, stable population and determined the strength of association between fibromyalgia and 7 comorbid conditions. Methods:We conducted a retrospective cohort study of a large, stable health insurance claims database (62,000 nationwide enrollees per year). Claims from 1997 to 2002 were examined using the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes to identify fibromyalgia cases (ICD code 729.1) and 7 predetermined comorbid conditions. Results:A total of 2595 incident cases of fibromyalgia were identified between 1997 and 2002. Age-adjusted incidence rates were 6.88 cases per 1000 person-years for males and 11.28 cases per 1000 person-years for females. Females were 1.64 times (95% confidence interval = 1.59–1.69) more likely than males to have fibromyalgia. Patients with fibromyalgia were 2.14 to 7.05 times more likely to have one or more of the following comorbid conditions: depression, anxiety, headache, irritable bowel syndrome, chronic fatigue syndrome, systemic lupus erythematosus, and rheumatoid arthritis. Conclusion:Females are more likely to be diagnosed with fibromyalgia than males, although to a substantially smaller degree than previously reported, and there are strong associations for comorbid conditions that are commonly thought to be associated with fibromyalgia.

Relationships between body mass indices and surgical replacements of knee and hip joints

BACKGROUND Osteoarthritis is both the most common form of arthritis and the most common reason for joint replacement surgery. Obese persons are believed to be more likely to develop generalized osteoarthritis that leads not only to knee but also to hip joint replacement surgeries. We hypothesized that obesity is also a risk for partial joint replacements and surgical revisions. METHODS A frequency-matched case-control study was conducted in Utah. Between 1992 and 2000, 840 hip and 911 knee joint replacement surgery patients, aged 55 to 74 years, were included in this study. Cases were randomly matched to 5578 controls, defined as Utah residents enrolled in a cancer screening trial. Odds ratios (ORs) were calculated using ICD-9 (International Classification of Diseases, 9th revision) procedural codes and body mass index (BMI) groups. RESULTS There was a strong association between increasing BMI and both total hip and knee replacement procedures. In males, the highest OR was for those weighing 37.50 to 39.99 kg/m(2) (total hip: OR=9.37, 95% confidence interval [CI] 2.64-33.31; total knee: OR=16.40; 95% CI 5, 19-51.86). In females, the highest OR was for those weighing > or =40 kg/m(2) (total hip: OR=4.47; 95% CI, 2.13-9.37; total knee: OR=19.05; 95% CI, 9.79-37.08). There were slight gender-specific differences in risk found for partial hip replacement procedures. Unexpectedly, no statistically significant association was found between obesity and the risk for hip or knee revision procedures. CONCLUSIONS While there is an association between obesity and hip and knee joint replacement surgeries, obesity does not appear to confer an independent risk for hip or knee revision procedures.

The effect of age at smoking initiation on lung cancer risk

It has been assumed that a younger age at initiation of cigarette smoking is associated with an increased risk of lung cancer, but previous studies have not adjusted for two strong risk factors, the amount smoked and duration smoked. We used data from a population-based case-control study with 282 histologically confirmed lung cancer cases matched to 3,282 random controls to determine whether age at initiation of smoking plays an independent role in the occurrence of lung cancer. After controlling for age, sex, and amount of tobacco exposure, men who began to smoke before age 20 had a substantially higher risk of developing lung cancer [odds ratio (OR) = 12.7; 95% confidence interval (CI) = 6.39–25.2] compared with men who began smoking at age 20 or older (OR = 6.03; 95% CI = 2.82–12.9). For women, the heavy increase in risk continued until age 25 (OR = 9.97; 95% CI = 4.68–21.2) compared with women who began smoking at age 26 or older (OR = 2.58; 95% CI = 0.5312.4). There was no predisposition toward a specific histologic type of lung cancer. In this study, up to 52.4% of lung cancer cases in men and up to 73.0% of lung cancer cases in women could be attributed to this effect of early age of first smoking. (Epidemiology 1993; 4:444–448)

Associations between body-mass index and surgery for rotator cuff tendinitis.

BACKGROUND Rotator cuff tendinopathy is a common entity. We hypothesized that obesity, because of biomechanical and systemic risk factors, increases the risks of rotator cuff tendinitis, tears, and related surgical procedures. METHODS A frequency-matched case-control study was conducted. Three hundred and eleven patients who were fifty-three to seventy-seven years old and who underwent rotator cuff repair, arthroscopy, and/or other repair of the shoulder in a large hospital from 1992 to 2000 were included in the study. These surgical procedures were used as proxies for the risk of rotator cuff tendinitis. These patients were age and frequency-matched to 933 controls, who were randomly drawn from a pool of 10,943 potential controls consisting of Utah state residents who were enrolled in a large cancer-screening trial. Age-adjusted odds ratios were calculated with use of the International Classification of Diseases, Ninth Revision procedural codes and body-mass-index groups. The data were stratified according to gender and age. Multiple linear regression analyses also were performed. RESULTS There was an association between increasing body-mass index and shoulder repair surgery. The highest odds ratios for both men (odds ratio = 3.13; 95% confidence interval = 1.29 to 7.61) and women (odds ratio = 3.51; 95% confidence interval = 1.80 to 6.85) were for individuals with a body-mass index of > or =35.0 kg/m(2). Tests for trend also were highly significant for both men (p = 0.002) and women (p < or = 0.001). Multiple linear regression analysis also indicated a significant association between increasing body-mass index and shoulder surgery (beta = 1.57; 95% confidence interval = 0.97 to 2.17; p < or = 0.001). CONCLUSIONS There is an association between obesity and shoulder repair surgery in men and women who are fifty-three to seventy-seven years of age. The results of the present study suggest that increasing body-mass index is a risk factor for rotator cuff tendinitis and related conditions.

Consensus Criteria for Screening Commercial Drivers for Obstructive Sleep Apnea : Evidence of Efficacy

Objective: To validate the recently published consensus criteria for screening commercial drivers for obstructive sleep apnea (OSA). Methods: A large, consecutive case series of commercial drivers was screened for OSA at a single occupational medicine clinic and those screening positive were referred for overnight polysomnography. Results: One hundred ninety (13%) of 1443 individuals having commercial motor vehicle driver examinations screened positive for OSA. None of these would have been detected if the only screening were the questions on the current Commercial Driver Medical examination form. One hundred thirty-four underwent polysomnography, and of those 94.8% had OSA, which is the best estimate of the positive predictive value of these consensus criteria in a population of truck drivers. Conclusion: The proposed screening criteria have a high positive predictive value in this population. This study lends support for the requirement to screen for OSA in commercial drivers.

The effect of maximum voluntary contraction on endurance times for the shoulder girdle

Abstract This study investigated endurance times as percentages of maximum voluntary contractions (MVCs) in 12 healthy females (mean 25.8±4.3 years) in 5 postures and at 7% MVCs. The shoulder postures utilized were 30/90 (shoulder forward flexion=30° and included elbow angle=90°), 60/90, 90/120, 120/150, and 150/180. The %MVCs were 5%, 15%, 30%, 45%, 60%, 75%, and 90% of MVC at each of these postures. Outcome measures included: endurance times, ratings of perceived exertion, fatigue ratings, pain ratings, and surface electromyography (trapezius and mid-deltoid). As expected the endurance time decreased non-linearly with an increase in %MVC. However, the relationship between endurance time and %MVC differed significantly from Rohmerts curve and suggests it considerably overestimates endurance times for %MVCs 45%. This studys curve did not become asymptotic even at 5% MVC. Shoulder posture (shoulder forward flexion angle) had a significant effect on endurance time. In general, endurance time decreased with an increase in shoulder flexion angle up to 120° and then it increased. Thus, overhead work (hands above the head) would appear to be better designed with a greater degree of forward flexion, rather than in front of the worker at lower degrees of forward flexion. Relevance to industry Published data on endurance times for the shoulder girdle are scant, yet shoulder injuries are neither rare nor inexpensive. This study completely redefines the relationship between endurance time and %MVC for the shoulder girdle. It will allow for a better definition of worker capabilities for the design of overhead work.

The Strain Index (SI) and Threshold Limit Value (TLV) for Hand Activity Level (HAL): risk of carpal tunnel syndrome (CTS) in a prospective cohort.

A cohort of 536 workers was enrolled from 10 diverse manufacturing facilities and was followed monthly for six years. Job physical exposures were individually measured. Worker demographics, medical history, psychosocial factors, current musculoskeletal disorders (MSDs) and nerve conduction studies (NCS) were obtained. Point and lifetime prevalence of carpal tunnel syndrome (CTS) at baseline (symptoms + abnormal NCS) were 10.3% and 19.8%. During follow-up, there were 35 new CTS cases (left, right or both hands). Factors predicting development of CTS included: job physical exposure (American conference of governmental industrial hygienists Threshold Limit Value (ACGIH TLV) for Hand Activity Level (HAL) and the Strain Index (SI)), age, BMI, other MSDs, inflammatory arthritis, gardening outside of work and feelings of depression. In the adjusted models, the TLV for HAL and the SI were both significant per unit increase in exposure with hazard ratios (HR) increasing up to a maximum of 5.4 (p = 0.05) and 5.3 (p = 0.03), respectively; however, similar to other reports, both suggested lower risk at higher exposures. Data suggest that the TLV for HAL and the SI are useful metrics for estimating exposure to biomechanical stressors. Practitioner Summary: This study was conducted to determine how well the TLV for HAL and the SI predict risk of CTS using a prospective cohort design with survival analysis. Both the TLV for HAL and the SI were found to predict risk of CTS when adjusted for relevant covariates.

Biomechanical risk factors for carpal tunnel syndrome: a pooled study of 2474 workers.

Background Between 2001 and 2010, five research groups conducted coordinated prospective studies of carpal tunnel syndrome (CTS) incidence among US workers from various industries and collected detailed subject-level exposure information with follow-up of symptoms, electrophysiological measures and job changes. Objective This analysis examined the associations between workplace biomechanical factors and incidence of dominant-hand CTS, adjusting for personal risk factors. Methods 2474 participants, without CTS or possible polyneuropathy at enrolment, were followed up to 6.5 years (5102 person-years). Individual workplace exposure measures of the dominant hand were collected for each task and included force, repetition, duty cycle and posture. Task exposures were combined across the workweek using time-weighted averaging to estimate job-level exposures. CTS case-criteria were based on symptoms and results of electrophysiological testing. HRs were estimated using Cox proportional hazard models. Results After adjustment for covariates, analyst (HR=2.17; 95% CI 1.38 to 3.43) and worker (HR=2.08; 95% CI 1.31 to 3.39) estimated peak hand force, forceful repetition rate (HR=1.84; 95% CI 1.19 to 2.86) and per cent time spent (eg, duty cycle) in forceful hand exertions (HR=2.05; 95% CI 1.34 to 3.15) were associated with increased risk of incident CTS. Associations were not observed between total hand repetition rate, per cent duration of all hand exertions, or wrist posture and incident CTS. Conclusions In this prospective multicentre study of production and service workers, measures of exposure to forceful hand exertion were associated with incident CTS after controlling for important covariates. These findings may influence the design of workplace safety programmes for preventing work-related CTS.

Personal and workplace psychosocial risk factors for carpal tunnel syndrome: a pooled study cohort.

Background Between 2001 and 2010, six research groups conducted coordinated multiyear, prospective studies of carpal tunnel syndrome (CTS) incidence in US workers from various industries and collected detailed subject-level exposure information with follow-up symptom, physical examination, electrophysiological measures and job changes. Objective This analysis of the pooled cohort examined the incidence of dominant-hand CTS in relation to demographic characteristics and estimated associations with occupational psychosocial factors and years worked, adjusting for confounding by personal risk factors. Methods 3515 participants, without baseline CTS, were followed-up to 7 years. Case criteria included symptoms and an electrodiagnostic study consistent with CTS. Adjusted HRs were estimated in Cox proportional hazard models. Workplace biomechanical factors were collected but not evaluated in this analysis. Results Women were at elevated risk for CTS (HR=1.30; 95% CI 0.98 to 1.72), and the incidence of CTS increased linearly with both age and body mass index (BMI) over most of the observed range. High job strain increased risk (HR=1.86; 95% CI 1.11 to 3.14), and social support was protective (HR=0.54; 95% CI 0.31 to 0.95). There was an inverse relationship with years worked among recent hires with the highest incidence in the first 3.5 years of work (HR=3.08; 95% CI 1.55 to 6.12). Conclusions Personal factors associated with an increased risk of developing CTS were BMI, age and being a woman. Workplace risk factors were high job strain, while social support was protective. The inverse relationship between CTS incidence and years worked among recent hires suggests the presence of a healthy worker survivor effect in the cohort.

Thyroid disease associated with exposure to the Nevada nuclear weapons test site radiation: A reevaluation based on corrected dosimetry and examination data

Background: A study was begun in 1965 to 1966 to determine whether children exposed to radioactive iodine from nuclear weapons testing at the Nevada Test Site from 1951 through 1962 were at higher risk of thyroid disease. In 1993, we reported that among those examined in 1985 to 1986 (Phase II) there was an association between radiation from the Nevada Test Site and thyroid neoplasms. Methods: We reevaluated the relationship between exposure to Nevada Test Site fallout and thyroid disease using newly corrected dose estimates and disease outcomes from the Phase II study. A prospective cohort of school children 12 to 18 years old living in Utah, Nevada, and Arizona was first examined for thyroid disease in 1965 to 1966 and reexamined in 1985 to 1986. In the Phase II report, 2497 subjects formed the basis for this analysis. Thyroid disease, including thyroid neoplasms and thyroiditis, was expressed as cumulative incidence and risk ratios (RRs) with a dose–response expressed as excess risk ratio (ERR/Gy). Results: The RR between thyroid radiation dose in the highest dose group and thyroid neoplasms increased from 3.4 (in the earlier analysis) to 7.5. The RR for thyroiditis increased from 1.1 to 2.7 with an ERR/Gy of 4.9 (95% confidence interval = 2.0 to 10.0). There were too few malignant thyroid neoplasms to estimate risk. Conclusions: Persons exposed to radioactive iodine as children have an increased risk of thyroid neoplasms and autoimmune thyroiditis up to 30 years after exposure.