Occupational injuries among aides and nurses in acute care.

BACKGROUND: Occupational injuries are common among nursing personnel. Most epidemiologic research on nursing aides comes from long-term care settings. Reports from acute care settings often combine data on nurses and aides even though their job requirements and personal characteristics are quite different. Our objective was to assess risk of work-related injuries in an acute care setting while contrasting injuries of aides and nurses. METHODS: A retrospective cohort of aides (n = 1,689) and nurses (n = 5,082) working in acute care at a large healthcare system between 1997 and 2004 were identified via personnel records. Workers' compensation filings were used to ascertain occupational injuries. Poisson regression was used to estimate rate ratios (RR) and 95% confidence intervals (95% CI). RESULTS: Aides had higher overall injury rates than nurses for no-lost work time (RR = 1.2, 95% CI: 1.1-1.3) and lost work time (RR = 2.8, 95% CI: 2.1-3.8) injuries. The risk of an injury due to lifting was greater among aides compared to nurses for both non-lost work time and lost work time injuries. Injury rates among aides were particularly high in rehabilitation and orthopedics units. Most of the injuries requiring time away from work for both groups were related to the process of delivering direct patient care. CONCLUSIONS: Our findings illustrate the importance of evaluating work-related injuries separately for aides and nurses, given differences in injury risk profiles and injury outcomes. It is particularly important that occupational safety needs of aides be addressed as this occupation experiences significant job growth.

Biomechanical allometry in hominoid thoracic vertebrae.

Considerable differences in spinal morphology have been noted between humans and other hominoids. Although comparative analyses of the external morphology of vertebrae have been performed, much less is known regarding variations in internal morphology (density) and biomechanical performance among humans and closely related non-human primates. In the current study we utilize density calibrated computed tomography images of thoracic vertebral bodies from hominoids (n=8-15 per species, human specimens 20-40 years of age) to obtain estimates of vertebral bone strength in axial compression and anteroposterior bending and to determine how estimates of strength scale with animal body mass. Our biomechanical analysis suggests that the strength of thoracic vertebral bodies is related to body mass (M) through power law relationships (y proportional, variant M(b)) in which the exponent b is 0.89 (reduced major axis) for prediction of axial compressive strength and is equal to 1.89 (reduced major axis) for prediction of bending strength. No differences in the relationship between body mass and strength were observed among hominoids. However, thoracic vertebrae from humans were found to be disproportionately larger in terms of vertebral length (distance between cranial and caudal endplates) and overall vertebral body volume (p<0.05). Additionally, vertebral bodies from humans were significantly less dense than in other hominoids (p<0.05). We suggest that reduced density in human vertebral bodies is a result of a systemic increase in porosity of cancellous bone in humans, while increased vertebral body volume and length are a result of functional adaptation during growth resulting in a vertebral bone structure that is just as strong, relative to body mass, as in other hominoids.

Lung cancer mortality and fibre exposures among North Carolina asbestos textile workers.

OBJECTIVE: To describe mortality among workers exposed to chrysotile asbestos and evaluate the relationship between lung cancer and asbestos fibre exposure. METHODS: Workers employed for at least 1 day between 1 January 1950 and 31 December 1973 in any of four plants in North Carolina, USA that produced asbestos textile products were enumerated. Vital status was ascertained through 31 December 2003. Historical exposures to asbestos fibres were estimated from work histories and 3578 industrial hygiene measurements taken in 1935-1986. Mortality of the cohort was compared with that of the national population via standardised mortality ratios (SMRs). Exposure-response relationships for lung cancer were examined within the cohort using Poisson regression to compute adjusted mortality rate ratios. RESULTS: Follow-up of 5770 workers included in the cohort resulted in 181 640 person-years of observation, with 2583 deaths from all causes and 277 from lung cancer. Mortality from all causes, all cancers and lung cancer was significant higher than expected, with SMRs of 1.47 for all causes, 1.41 for all cancer and 1.96 (95% CI 1.73 to 2.20) for lung cancer. SMRs for pleural cancer, mesothelioma and pneumoconiosis were also elevated. The risk of lung cancer and asbestosis increased with cumulative fibre exposure (RR 1.102 per 100 fibre-year/ml, 95% CI 1.044 to 1.164, and RR 1.249 per 100 fibre-year/ml, 95% CI 1.186 to 1.316, respectively, for total career exposure). CONCLUSIONS: This study provides further evidence that exposure to chrysotile asbestos in textile manufacturing is associated with increased risk of lung cancer, asbestosis cancer of the pleura and mesothelioma.

Estimates of historical exposures by phase contrast and transmission electron microscopy in North Carolina USA asbestos textile plants.

OBJECTIVES: To develop a job-exposure matrix (JEM) for fibre exposures in three asbestos textile plants and to develop estimates of fibre size-specific exposures. METHODS: Historical dust samples from three North Carolina, USA asbestos textile plants were obtained. Plant specific samples were used to express impinger dust concentrations as fibre concentrations by phase contract microscopy (PCM). Mixed models were used to estimate PCM exposures by plant, department, job and calendar time. Archived membrane filter samples were analysed by transmission electron microscopy (TEM) to determine the bivariate diameter/length distribution of airborne fibres by plant and operation. RESULTS: PCM fibre levels estimated from the models were very high in the 1930s, with some operations having in excess of 200 fibres/ml, and decreased appreciably over time. TEM results for 77 airborne dust samples found that only a small proportion of airborne fibres were measured by PCM (>0.25 microm in diameter and >5 microm in length) and the proportion varied considerably by plant and operation (range 2.9% to 10.0%). The bivariate diameter/length distribution of airborne fibres demonstrated a relatively high degree of variability by plant and operation. PCM adjustment factors also varied substantially across plants and operations. CONCLUSIONS: These data provide new information concerning airborne fibre levels and characteristics in three historically important asbestos textile plants. PCM concentrations were high in the early years and TEM data demonstrate that the vast majority of airborne fibres inhaled by the workers were shorter than 5 microm in length, and thus not included in the PCM-based fibre counts.

A case crossover study of triggers for hand injuries in commercial fishing.

OBJECTIVES: Previous studies estimate hand and wrist injuries are common in commercial fishing. Risk factors including working with catch, handling gear and slips or falls, have been identified from activity and injury contact reports, but no studies have examined the influence of transient risk factors, or triggers. This case crossover study design was conducted to investigate triggers for acute hand trauma in commercial fishing. METHODS: A case crossover study was nested within a previously established prospective cohort of 217 southeastern United States commercial fishermen followed from April 1999 through October 2001. Hand injury cases and controls were matched using three control selection strategies. Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated to determine if transient risk factors such as glove use, engaging in more than one type of fishing, maintenance activities and other covariates of interest increased the risk of occupational traumatic hand/wrist/digit injuries. RESULTS: 21% (46/217) of fishermen reported one or more hand/wrist/digit injuries, yielding 65 eligible cases. Performing maintenance work (any vs none) (OR 3.1, 95% CI 1.8 to 5.5) and using multiple types of fishing equipment in comparison to using only one type (OR 1.9, 95% CI 0.9 to 3.8) were associated with increased risk of hand/wrist/digit injury. There was no evidence glove use was protective (any vs none) for hand/wrist/digit injury (OR 0.9, 95% CI 0.5 to 1.7). CONCLUSIONS: The case crossover design is a useful method to determine triggers of commercial fishing-related hand/wrist/digit injuries. Maintenance work was strongly associated with hand/wrist/digit injury for these fishermen.

Development of a fibre size-specific job-exposure matrix for airborne asbestos fibres.

OBJECTIVE: To develop a method for estimating fibre size-specific exposures to airborne asbestos dust for use in epidemiological investigations of exposure-response relations. METHODS: Archived membrane filter samples collected at a Charleston, South Carolina asbestos textile plant during 1964-8 were analysed by transmission electron microscopy (TEM) to determine the bivariate diameter/length distribution of airborne fibres by plant operation. The protocol used for these analyses was based on the direct transfer method published by the International Standards Organization (ISO), modified to enhance fibre size determinations, especially for long fibres. Procedures to adjust standard phase contrast microscopy (PCM) fibre concentration measures using the TEM data in a job-exposure matrix (JEM) were developed in order to estimate fibre size-specific exposures. RESULTS: A total of 84 airborne dust samples were used to measure diameter and length for over 18,000 fibres or fibre bundles. Consistent with previous studies, a small proportion of airborne fibres were longer than >5 microm in length, but the proportion varied considerably by plant operation (range 6.9% to 20.8%). The bivariate diameter/length distribution of airborne fibres was expressed as the proportion of fibres in 20 size-specific cells and this distribution demonstrated a relatively high degree of variability by plant operation. PCM adjustment factors also varied substantially across plant operations. CONCLUSIONS: These data provide new information concerning the airborne fibre characteristics for a previously studied textile facility. The TEM data demonstrate that the vast majority of airborne fibres inhaled by the workers were shorter than 5 mum in length, and thus not included in the PCM-based fibre counts. The TEM data were used to develop a new fibre size-specific JEM for use in an updated cohort mortality study to investigate the role of fibre dimension in the development of asbestos-related lung diseases.

Cost of injuries from a prospective cohort study of North Carolina high school athletes.

OBJECTIVE: To estimate the economic cost of injuries in a population of US high school varsity athletes. DESIGN AND SETTING: The North Carolina High School Athletic Injury Study, conducted from 1996 to 1999, was a prospective cohort study of injury incidence and severity. A two-stage cluster sampling technique was used to select athletic teams from 100 high schools in North Carolina. An injury cost model was used to estimate the economic cost of injury. PARTICIPANTS: Varsity athletes from 12 sports: football, girls' and boy's soccer, girls' and boys' track, girls' and boy's basketball, baseball, softball, wrestling, volleyball, and cheerleading. MAIN OUTCOME MEASURES: Descriptive data were collected at the time of injury. Three types of costs were estimated: medical, human capital (medical costs plus loss of future earnings), and comprehensive (human capital costs plus lost quality of life). RESULTS: The annual statewide estimates were $9.9 million in medical costs, $44.7 million in human capital costs, and $144.6 million in comprehensive costs. The mean medical cost was $709 per injury (95% CI $542 to $927), $2223 per injury (95% CI $1709 to $2893) in human capital costs, and $10,432 per injury (95% CI $8062 to $13,449) in comprehensive costs. Sport and competition division were significant predictors of injury costs. CONCLUSIONS: Injuries among high school athletes represent a significant economic cost to society. Further research should estimate costs in additional populations to begin to develop cost-effective sports injury prevention programs.

Incidence of allergy and allergy symptoms among workers exposed to laboratory animals.

BACKGROUND AND AIMS: Few studies have described relations between exposure to laboratory animals and the incidence of laboratory animal allergy (LAA). Studies that have found exposure-response relations have been cross sectional in design or have focused on exposure to rats and mice. This study used longitudinal data collected over a 12 year period to describe the relations between indices of exposure to laboratory animals and the development of LAA and LAA symptoms. METHODS: Data were obtained from questionnaires and serological laboratory results from a dynamic cohort of workers exposed to a variety of laboratory animals in a pharmaceutical manufacturing company. Poisson regression was used to model the incidence rate ratios of species specific and general LAA and LAA symptoms at different levels of exposure. RESULTS: The 12 year incidence rates of LAA symptoms and LAA for all workers were 2.26 (95% CI 1.61 to 2.91) and 1.32 (95% CI 0.76 to 1.87) per 100 person-years, respectively. Higher rate ratios were seen with increasing reported hours of exposure to tasks that required working with animal cages or with many animals at one time. The most common symptoms were related to rhinitis rather than to asthma. CONCLUSIONS: This study suggests that the risk of LAA increases with duration of exposure to animals and work in animal related tasks. Incidence might be reduced by limiting hours per week of exposure to laboratory animals.

Relation between ambient air quality and selected birth defects, seven county study, Texas, 1997-2000.

A population-based case-control study investigated the association between maternal exposure to air pollutants, carbon monoxide, nitrogen dioxide, ozone, sulfur dioxide, and particulate matter <10 microm in aerodynamic diameter during weeks 3-8 of pregnancy and the risk of selected cardiac birth defects and oral clefts in livebirths and fetal deaths between 1997 and 2000 in seven Texas counties. Controls were frequency matched to cases on year of birth, vital status, and maternal county of residence at delivery. Stationary monitoring data were used to estimate air pollution exposure. Logistic regression models adjusted for covariates available in the vital record. When the highest quartile of exposure was compared with the lowest, the authors observed positive associations between carbon monoxide and tetralogy of Fallot (odds ratio = 2.04, 95% confidence interval: 1.26, 3.29), particulate matter <10 microm in aerodynamic diameter and isolated atrial septal defects (odds ratio = 2.27, 95% confidence interval: 1.43, 3.60), and sulfur dioxide and isolated ventricular septal defects (odds ratio = 2.16, 95% confidence interval: 1.51, 3.09). There were inverse associations between carbon monoxide and isolated atrial septal defects and between ozone and isolated ventricular septal defects. Evidence that air pollution exposure influences the risk of oral clefts was limited. Suggestive results support a previously reported finding of an association between ozone exposure and pulmonary artery and valve defects.

Poisson regression analysis of ungrouped data.

BACKGROUND: Poisson regression is routinely used for analysis of epidemiological data from studies of large occupational cohorts. It is typically implemented as a grouped method of data analysis in which all exposure and covariate information is categorised and person-time and events are tabulated. AIMS: To describe an alternative approach to Poisson regression analysis using single units of person-time without grouping. METHODS: Data for simulated and empirical cohorts were analysed by Poisson regression. In analyses of simulated data, effect estimates derived via Poisson regression without grouping were compared to those obtained under proportional hazards regression. Analyses of empirical data for a cohort of 138 900 electrical workers were used to illustrate how the ungrouped approach may be applied in analyses of actual occupational cohorts. RESULTS: Using simulated data, Poisson regression analyses of ungrouped person-time data yield results equivalent to those obtained via proportional hazards regression: the results of both methods gave unbiased estimates of the "true" association specified for the simulation. Analyses of empirical data confirm that grouped and ungrouped analyses provide identical results when the same models are specified. However, bias may arise when exposure-response trends are estimated via Poisson regression analyses in which exposure scores, such as category means or midpoints, are assigned to grouped data. CONCLUSIONS: Poisson regression analysis of ungrouped person-time data is a useful tool that can avoid bias associated with categorising exposure data and assigning exposure scores, and facilitate direct assessment of the consequences of exposure categorisation and score assignment on regression results.

Ecological associations between asthma prevalence and potential exposure to farming.

Farming and exposure to livestock have been proposed as protective against the development of asthma in children. An ecological study was conducted to examine the support for these relationships in the USA. County-specific aggregate measures were used to examine the relationship between the prevalence of asthma and wheeze in 7th and 8th grade school children (aged 12-14 yrs) and selected measures of potential exposure to farming in the state of North Carolina. Binomial regression models were fitted to quantify these relationships, with adjustments for parental smoking, socioeconomic status, sex and race. Regression coefficients were reported for an increment of one interquartile range (IQR) in each indicator of exposure. The prevalence of asthma showed decreasing trends for most indicators of farm exposure. Regression results suggested that the largest decreases in asthma prevalence were associated with the number of farms (-5.0% per IQR increment), acreage of hay (-7.2% per IQR increment) and beef cattle (-7.8% per IQR increment). The pattern of results was similar for wheezing. In conclusion, the findings of this study are consistent with the hypothesis that certain farm exposures are protective against childhood asthma. Further research with individual-level data is needed to identify the specific protective exposures.

The impact of exposure categorisation for grouped analyses of cohort data.

BACKGROUND: Poisson regression is routinely used in occupational and environmental epidemiology. For typical Poisson regression analyses, person-time and events are tabulated by categorising predictor variables that were originally measured on a continuous scale. In order to estimate a dose-response trend, a researcher must decide how to categorise exposures and how to assign scores to exposure groups. AIMS: To investigate the impact on regression results of decisions about exposure categorisation and score assignment. METHODS: Cohort data were generated by Monte Carlo simulation methods. Exposure categories were defined by quintiles or deciles of the exposure distribution. Scores were assigned to exposure groups based on category midpoint and mean exposure levels. Estimated exposure-disease trends derived via Poisson regression were compared to the "true" association specified for the simulation. RESULTS: Under the assumption that exposures conform to a lognormal or exponential distribution, trend estimates tend to be negatively biased when scores are assigned based on category midpoints and positively biased when scores are assigned based on cell specific mean values. The degree of bias was greater when exposure categories were defined by quintiles of the exposure distribution than when categories were defined by deciles of the exposure distribution. CONCLUSIONS: The routine practice of exposure categorisation and score assignment introduces exposure misclassification that may be differential with respect to disease status and, consequently, lead to biased exposure-disease trend estimates. When using the Poisson regression method to evaluate exposure-disease trends, such problems can be minimised (but not necessarily eliminated) by forming relatively refined exposure categories based on percentiles of the exposure distribution among cases, and by assigning scores to exposure categories that reflect person-time weighted mean exposure levels.

Work related injuries in small scale commercial fishing.

OBJECTIVE: To describe the epidemiology of work related injury in a group of small scale, independent commercial fishers. DESIGN: Cross sectional survey (baseline instrument of a prospective cohort study). SETTING AND SUBJECTS: Commercial fishers in eastern North Carolina. RESULTS: A cohort of 219 commercial fishers was established and 215 subjects completed an injury questionnaire. The main types of fishing conducted by the cohort were finfishing (159/215) and crabbing (154/215). Of the 215 fishers, 83 reported that they had suffered an injury event in the previous 12 months, a retrospective recall incidence proportion of 38.6 per 100 workers (95% confidence interval 32.1 to 45.1). The 83 injury events resulted in 94 injuries; 47% were penetrating wounds and 24% were strains/sprains. Half of injuries were to the hand/wrist/digits and 13% were to the back. Of the penetrating wounds, 87% were to the hand/wrist/digits, 32% became infected, and 80% were caused by contact with finfish, shellfish, or other marine animal. Of the strains/sprains, 48% were to the back and 26% were to the shoulder. Seventy percent of strains/sprains were caused by moving heavy objects, mainly either while hauling in nets, pots, or lines or loading/unloading the boat. CONCLUSION: In this group of small scale, independent fishers, the most common reported injuries were penetrating wounds to the hand/wrist/digits from marine animals and strains/sprains to the back while moving heavy objects.

Deindustrialisation and the long term decline in fatal occupational injuries.

AIMS: To examine the extent to which deindustrialisation accounts for long term trends in occupational injury risk in the United States. METHODS: Rates of fatal unintentional occupational injury were computed using data from death certificates and the population census. Trends were estimated using Poisson regression. Standardisation and regression methods were used to adjust for the potential effect of structural change in the labour market. RESULTS: The fatal occupational injury rate for all industries declined 45% from 1980 to 1996 (RR (rate ratio) 0.55, 95% CI 0.52 to 0.57). Adjustment for structural changes in the workforce shifted the RR to 0.62 (95% CI 0.60 to 0.65). Expanding industries enjoyed more rapid reduction in risk (-3.43% per year, 95% CI -3.62 to -3.24) than those that contracted (-2.65% per year, 95% CI -2.88 to -2.42). CONCLUSIONS: Deindustrialisation contributed to the decline of fatal occupational injury rates in the United States, but explained only 10-15% of the total change.

Diversity of trends in occupational injury mortality in the United States, 1980-96.

OBJECTIVES: Although the United States has generally enjoyed declining rates of fatal occupational injury, the rate of decline has not been uniform. To examine the heterogeneity of trends, changes in fatal occupational injury rates from 1980 to 1996 were estimated by occupation, industry, geographic region, and demographic group. METHODS: Deaths due to injury at work during 1980-96 were identified from the US National Traumatic Occupational Fatality database and populations at risk were estimated from the census of population. Mortality rates were computed for unintentional injuries, homicides, and all injuries combined. The annual rate of change was estimated using Poisson regression to model the death rate as a function of time. RESULTS: The estimated average rates for all fatal occupational injuries and for unintentional injuries declined by 3% per year, while the estimated rate of homicide declined <1% per year. The improvement was faster for men (3% per year) than for women (<1% per year) and for younger relative to older workers (7% per year v 2%-3% per year). Trends were also geographically heterogeneous, with the most rapid declines (7%-8% per year) in the South and West. Injury rates for most occupations and industries declined at near the average rate, but some experienced no change or an increase. The rate of homicide also increased in a number of occupations and industries. CONCLUSIONS: Broad downward trends in occupational fatality rates may be explained by several factors, including organized safety efforts, product and process changes, and the ongoing shift of employment toward safer sectors. Disparities in fatal injury trends draw attention to potential opportunities to reduce risk: work settings with increasing injury rates are of particular concern.

Use of protective equipment in a cohort of rugby players.

PURPOSE: To describe the level of usage of protective devices and equipment in a cohort of New Zealand rugby players. METHODS: Male and female players (N = 327) from a range of competitive grades were followed over the course of the season. Participants were interviewed weekly about their participation in rugby and use of protective equipment. The main outcome measure was percentage of all player-weeks of follow-up for which each equipment item was used. RESULTS: Mouthguards, the most commonly used equipment item, were worn for 64.9% of player-weeks. Mouthguard usage ranged from 55.0% of player-weeks in Schoolgirls grade to 72.9% of player-weeks in Senior A competition. The next most common item was taping of body joints (23.7% of player-weeks). The sites most commonly taped were the ankle, knee, and hand. Overall usage for the other protective equipment items studied (shin guards, padded headgear, head tape, support sleeves, and grease) was below 15%. In general, forwards had higher usage of protective equipment than backs, and male players had higher usage than female players. The most common self-reported reasons for using protective equipment were to prevent injury and because of a past injury. Players exhibited considerable week-to-week variation in their usage of protective equipment. CONCLUSIONS: In general, equipment usage was highest in those at greatest risk of injury, namely, forwards, male players, and the senior grades. The high voluntary use of mouthguards is encouraging and indicative of a base of player support for their role in this sport.

Exposure to extremely low frequency magnetic fields among working women and homemakers.

Given concerns with potential health effects of exposure to magnetic fields, the goal of this study was to examine the magnitude and sources of occupational and residential exposure to extremely low frequency (primarily 60 Hz) magnetic fields among women. Exposure to 60 Hz magnetic fields was surveyed among cases and controls recruited for a study of breast cancer in 25 counties in North Carolina. The 273 women who participated wore an integrating personal magnetic-field exposure meter (AMEX 3-D) that measured their time-weighted average (TWA) exposure. A questionnaire was administered to determine the duration and frequency of electric appliance and machinery use. The geometric mean (GM) of the TWA exposure for employed women was 0.138 microT (range 0.022-3.636 microT) and for homemakers 0.113 microT (range 0.022-0.403 microT). Women working in manufacturing and industrial facilities had the highest exposure (GM 0.265 microT, range 0.054-3.436 microT), while nurses and health technicians (GM 0.134 microT, range 0.032-0.285 microT) and teachers and school administrators (GM 0.099 microT, range 0.035-0.673 microT) had the lowest exposures. Job titles, unless very limited in scope and/or environment, self-reported information about equipment use, potential exposure sources, time, and distance were not good predictors of magnetic-field exposure. Furthermore, the results show that occupations previously observed to have increased risk of breast cancer, such as teachers, nurses, administrative support, and housewives, did not have elevated average magnetic field exposures. Therefore, it is questionable whether exposure to power frequency magnetic fields is the cause of the increased breast cancer risk seen in these occupations.