The impact of rest breaks on temporal trends in injury risk

This study examined the impact of rest breaks on temporal trends in industrial accident risks in an attempt to replicate earlier findings of a linear increase in risk as a function of elapsed time on task. In two separate studies, the trend in work-related injuries were studied in relation to the timing of rest breaks. In study one, comparisons were made between on- and off-track workers on weekly rotating three-shift systems operating in a large engineering company. Records of on-duty injuries that occurred over 12 months were examined (N = 4645 incidents). Study two involved interviewing patients who had suffered work-related hand injuries in a variety of occupational settings (N = 407 patients). Hierarchical log linear analysis was used in both studies. In study one, risk increased from the first to the second half-hour of continuous work following a break, but then remained relatively constant in subsequent half-hour periods, although there was a fall in the third half-hour for on-track workers. In some of the data, there was also a decrease in risk in the period leading up to the end of a work period. There was a sharp decline in reported injuries toward the very end of a shift, but otherwise the observed trends did not differ between successive periods of continuous work or between morning, afternoon, and night shifts. In study two, risk increased from the first to the second half-hour of continuous work and then remained relatively constant in the third half-hour. The contrast between the current and previous findings may be due to the relatively unique work environment of the previous study. It is suggested that the current trends reflect the effects of working in a relatively unconstrained task environment, and that causes other than fatigue may underlie the trends observed in both the previous and current studies.     

Updating the “Risk Index”: A systematic review and meta-analysis of occupational injuries and work schedule characteristics

Fatigue is a major risk factor for occupational ‘accidents’ and injuries, and involves dimensions of physical, mental, and muscular fatigue. These dimensions are largely influenced by temporal aspects of work schedules. The “Risk Index” combines four fatigue-related components of work schedules to estimate occupational ‘accident’ and injury risk based on empirical trends: shift type (morning, afternoon/evening, night), length and consecutive number, and on-shift rest breaks. Since its first introduction in 2004, several additional studies have been published that allow the opportunity to improve the internal and external validity of the “Risk Index”. Thus, we updated the model’s estimates by systematically reviewing the literature and synthesizing study results using meta-analysis. Cochrane Collaboration directives and MOOSE guidelines were followed. We conducted systematic literature searches on each model component in Medline. An inverse variance approach to meta-analysis was used to synthesize study effect sizes and estimate between-studies variance (‘heterogeneity’). Meta-regression models were conducted to explain the heterogeneity using several effect modifiers, including the sample age and sex ratio. Among 3,183 initially identified abstracts, after screening by two independent raters (95–98% agreement), 29 high-quality studies were included in the meta-analysis. The following trends were observed: Shift type. Compared to morning shifts, injury risk significantly increased on night shifts (RR = 1.36 [95%CI = 1.15–1.60], n = 14 studies), while risk was slightly elevated on afternoon/evening shifts, although non-significantly (RR = 1.12 [0.76–1.64], n = 9 studies). Meta-regressions revealed worker’s age as a significant effect modifier: adolescent workers (≤ 20 y) showed a decreased risk on the afternoon/evening shift compared to both morning shifts and adult workers (p < 0.05). Number of consecutive shifts. Compared to the first shift in a block of consecutive shifts, risk increased exponentially for morning shifts (e.g., 4th: RR = 1.09 [0.90–1.32]; n = 6 studies) and night shifts (e.g., 4th: RR = 1.36 [1.14–1.62]; n = 8 studies), while risk on afternoon/evening shifts appeared unsystematic. Shift length. Injury risk rose substantially beyond the 9th hour on duty, a trend that was mirrored when looking at shift lengths (e.g., >12 h: RR = 1.34 [1.04–1.51], n = 3 studies). Rest breaks. Risk decreased for any rest break duration (e.g., 31–60 min: RR = 0.35 [0.29–0.43], n = 2 studies). With regards to time between breaks, risk increased with every additional half hour spent on the work task compared to the first 30 min (e.g., 90–119 min: RR = 1.62 [1.00–2.62], n = 3 studies). Rest break duration and interval seem to interact such that with increasing duration, the time between breaks becomes irrelevant. The updated “Risk Index”. All four components were combined to form the updated model and the relative risk values estimated for a variety of work schedules. The resulting “Risk Map” shows regions of highest risk when rest breaks are not taken frequently enough (i.e. <4 h) or are too short (i.e. <30 min), when shift length exceeds 11 h, and when work takes place during the night (particularly for >3 consecutive night shifts). The “Risk Index” is proposed as an empirical model to predict occupational ‘accident’ and injury risk based on the most recent data in the field, and can serve as a tool to evaluate hazards and maximize safety across different work schedules.     

The influence of visual display terminal use on the physical and mental conditions of administrative staff in Japan

Visual display terminals (VDT) are standard equipment for many office workers. Their use, however, may increase the risk of developing adverse conditions related to vision, the musculoskeletal system, and mental health. We carried out a survey among 3070 workers aged 18 to 67 years (mean, 39.9 years) at a prefectural administrative office, in which 76% of subjects were visual display terminal (VDT) users. We examined the relationship between duration of daily VDT use and eyestrain, neck or upper extremity pain, back pain, and mental health, and estimated the effect of breaks and rest during VDT work on these symptoms. The 12-item General Health Questionnaire (GHQ-12: total scores ranged from 0 to 12) was used to identify potential poor mental health status, and subjects with 4 or more were considered to have symptoms of psychological distress. Seventeen percent of subjects reported eyestrain, 19.1% reported upper extremity pain, 11.6% reported back pain, and 17% of subjects had GHQ-12 scores of 4 or higher. Logistic regression analysis showed that duration of daily VDT use and lack of breaks and rest during VDT work were significantly associated with eyestrain, neck or upper extremity pain, back pain, and psychological distress. In order to protect users from the adverse effects associated with VDT work, reducing daily VDT exposure, taking breaks, and rest during VDT work are important.     

Smoking among Shift Workers: More Than a Confounding Factor

In studies on the cardiovascular disease risk among shift workers, smoking is considered to be a confounding factor. In a study of 239 shift and 157 daytime workers, it was found that shift work was prospectively related to increased cigarette consumption, indicating that smoking might be in the causative pathway; however, the number of study subjects was too low to warrant sound conclusions. Therefore, data from the Maastricht Cohort study were used to investigate the longitudinal relation between smoking and shift work in a much larger population. In this study, a total of 12,140 employees were followed for two years by means of self‐administered questionnaires. The authors compared workers who normally worked during daytime hours only (74%) with those who worked other than day shifts (26%). Logistic regression analyses were performed, adjusting for demographic factors of age, gender, and educational level to evaluate the risk of starting to smoke (n=25) in the group of non‐smoking workers and the risk of quitting (n=318) in the group of smoking workers. Logistic regression analysis showed a significant association between shift work and taking up smoking during the two‐year follow‐up (odds ratio: 1.46, p=0.03). The risk to stop smoking was somewhat lower in shift workers (odds ratio: 0.91) but not statistically significant (p=0.5). To conclude, this study showed that, independent of educational level, shift workers are more prone to start smoking. This finding might have important implications for studies on the health effects of shift workers and for possible interventions aimed at the reduction of the excess health risk among shift workers.     

The Use of Actimetry to Assess Changes to the Rest–Activity Cycle

The endogenous circadian oscillator (the body clock) is slow to adjust to altered rest–activity patterns. As a result, several negative consequences arise during night work and after time‐zone transitions. The process of adjustment can be assessed by measurements of the sleep electroencephalogram (EEG), core temperature or melatonin secretion, for example, but these techniques are very difficult to apply in field studies, and make very great demands upon both experimenters and subjects. We have sought to establish if the activity record, measured conveniently and unobtrusively by a monitor attached to the wrist, can be treated in ways that enable estimates to be made of the disruption caused by changes to the rest–activity cycle, and the process of adjustment to them. In Part A, we describe the calculation and assessment of a series of “activity indices” that measure the overall activity pattern, activity when out of bed or in bed, or the activity in the hours adjacent to going to bed or getting up. The value of the indices was assessed by measuring changes to them in subjects undergoing night work or undergoing time‐zone transitions. In both cases, there is a large body of literature describing the changes that would be expected. First, night workers (working 2 to 4 successive night shifts) were investigated during rest days and night shifts. The indices indicated that night work was associated with lower activity when the subjects were out of bed and higher activity when in bed. Some indices also measured when subjects took an afternoon nap before starting a series of night shifts and gave information about the process of adjustment to night work and recovery from it. Second, in studies from travelers crossing six or more time zones to the east or west, the indices indicated that there were changes to the rest–activity cycle immediately after the flights, both in its overall profile and when activity of the subjects in bed or out of bed was considered, and that adjustment took place on subsequent days. By focusing on those indices describing the activity records during the last hour in bed (LHIB) and the first hour out of bed (FHOB), some evidence was found for incomplete adjustment of the body clock, and for differences between westward and eastward flights. In Part B, the battery of indices are applied to the activity records of long‐haul pilots, whose activity patterns showed a mixture of effects due to night work and time‐zone transitions. Actimetry was performed during the flights themselves and during the layover days (which were either rest or work days). The indices indicated that all pilots had disrupted rest–activity cycles caused by night flights, and that there were added problems for those who had also undergone time‐zone transitions. Rest days were valuable for normalizing the activity profile. For those pilots who flew to the west, adjustment was by delay, though not all aspects of the rest–activity cycle adjusted immediately; for those who flew to the east, some attempted to advance their rest–activity cycle while others maintained home‐based activity profiles. The indices indicated that the activity profile was disrupted more in those pilots who attempted to advance their rest–activity cycle. We conclude that objective estimates of the disruption caused to the rest–activity cycle and the circadian system can be obtained by suitable analysis of the activity record.     

Shift Work,Safety, and Aging

It has long been recognized that older shift workers may have shorter and more disturbed day sleeps between successive night shifts than their younger colleagues. This has given rise to considerable concern over the safety of aging shift workers because of the increasing age of the work force and increases in retirement age. Because there have been no direct studies of the combined effects of shift work and age on safety, the present paper begins by reviewing the literature relating safety to features of shift systems. It then considers the general effect of age on occupational injury rates before examining existing evidence of the combined effects of shift work and age on performance capabilities. The results of the literature review indicate that when the a priori risk is constant, there is reasonably clear evidence that injury rates are higher at night, and that they increase over successive night shifts more rapidly than over successive day shifts. Further, although occupational injuries are less frequent in older workers, those that do occur tend to be more serious. Finally, there is some suggestive evidence from studies of objectively measured performance capabilities that older workers may be less able to both maintain their performance over the course of a night shift and cope with longer spans of successive night shifts. It is concluded that it seems possible, even though unproven as yet, that older workers may be at greater risk both to injury and accident on the night shift. There is a strong need for future epidemiological studies of the combined effects of shift work and age on injuries and accidents, and that these should attempt to separate the effects of age per se from those of generation.     

Shift work, safety, and aging

It has long been recognized that older shift workers may have shorter and more disturbed day sleeps between successive night shifts than their younger colleagues. This has given rise to considerable concern over the safety of aging shift workers because of the increasing age of the work force and increases in retirement age. Because there have been no direct studies of the combined effects of shift work and age on safety, the present paper begins by reviewing the literature relating safety to features of shift systems. It then considers the general effect of age on occupational injury rates before examining existing evidence of the combined effects of shift work and age on performance capabilities. The results of the literature review indicate that when the a priori risk is constant, there is reasonably clear evidence that injury rates are higher at night, and that they increase over successive night shifts more rapidly than over successive day shifts. Further, although occupational injuries are less frequent in older workers, those that do occur tend to be more serious. Finally, there is some suggestive evidence from studies of objectively measured performance capabilities that older workers may be less able to both maintain their performance over the course of a night shift and cope with longer spans of successive night shifts. It is concluded that it seems possible, even though unproven as yet, that older workers may be at greater risk both to injury and accident on the night shift. There is a strong need for future epidemiological studies of the combined effects of shift work and age on injuries and accidents, and that these should attempt to separate the effects of age per se from those of generation.     

Who Is Too Old for Shift Work? Developing Better Criteria

Demographic and social trends in industrialized countries are expected to lead to increasing numbers of older shift workers, raising concerns about possible health and safety risks. For older night workers, the International Labour Organization has recommended options for transferring to day work or early retirement, but few States have adopted these measures. For commercial air transport pilots, the International Civil Aviation Organization has implemented a series of regulatory measures that could manage the risks associated with aging, including a mandatory retirement age, regular medical assessments for fitness to fly, and limits on the duration of duty and rest. Each of these approaches has strengths and weaknesses. The mandatory retirement age is effectively arbitrary, has been controversial, and was recently increased from 60 to 65 yrs for one member of a two‐person cockpit crew. Medical assessments offer a more individualized approach, but to improve safety, they must address aspects of health and physical or mental function that affect work performance and safety outcomes. The traditional focus has been on cardiovascular risk factors, although cardiac incapacitation is not a cause of accidents in a two‐person cockpit aircraft. On the other hand, while pilot fatigue is an acknowledged cause of accidents, there is currently no requirement to consider issues associated with fatigue or sleep problems in fitness‐to‐fly medical assessments. Older long‐haul pilots show greater sleep fragmentation than their younger colleagues and those in the general population. Sleep becomes more fragmented with increasing age, but the functional significance of this remains unclear. Among younger adults, experimental sleep fragmentation leads to increased sleepiness and degradation of performance and mood. Greater sleep loss is reported by older long‐haul pilots, as well as other older shift workers, compared to younger people working similar duty patterns. Experimental sleep restriction causes a degradation of performance and mood that is cumulative and dose‐dependent. In addition, a recent large‐scale flight simulation study indicates that the duration of sleep obtained by individual pilots is an independent predictor of crew performance in a two‐person cockpit. Based on these considerations, we propose that fatigue and sleep‐related issues should become a standard part of fitness‐for‐work medical assessments, particularly for older shift workers. A multi‐layered approach is proposed, with a routine structured sleep history leading to referral to specialist sleep services where appropriate. Criteria for specialist referral and medical retirement should be related to the workplace risk represented by an older worker. Additional research is needed to develop and validate sleep‐related criteria for assessing fitness for work. For example, a better understanding of the effects of sleep fragmentation on the waking function of older workers might lead to a fragmentation threshold for fitness for work. The potential negative effects of unemployment and early retirement also need to be taken into account when considering the options for managing the occupational health and safety needs of older shift workers.     

Smoking among shift workers: More than a confounding factor

In studies on the cardiovascular disease risk among shift workers, smoking is considered to be a confounding factor. In a study of 239 shift and 157 daytime workers, it was found that shift work was prospectively related to increased cigarette consumption, indicating that smoking might be in the causative pathway; however, the number of study subjects was too low to warrant sound conclusions. Therefore, data from the Maastricht Cohort study were used to investigate the longitudinal relation between smoking and shift work in a much larger population. In this study, a total of 12,140 employees were followed for two years by means of self-administered questionnaires. The authors compared workers who normally worked during daytime hours only (74%) with those who worked other than day shifts (26%). Logistic regression analyses were performed, adjusting for demographic factors of age, gender, and educational level to evaluate the risk of starting to smoke (n=25) in the group of non-smoking workers and the risk of quitting (n=318) in the group of smoking workers. Logistic regression analysis showed a significant association between shift work and taking up smoking during the two-year follow-up (odds ratio: 1.46, p=0.03). The risk to stop smoking was somewhat lower in shift workers (odds ratio: 0.91) but not statistically significant (p=0.5). To conclude, this study showed that, independent of educational level, shift workers are more prone to start smoking. This finding might have important implications for studies on the health effects of shift workers and for possible interventions aimed at the reduction of the excess health risk among shift workers.     

Toward a “Risk Index” to Assess Work Schedules

This article describes our preliminary attempt to develop a Risk Index to estimate the risk of human error on different work schedules based on trends in the relative risk of accidents and injuries, rather than on hypothetical intervening variables such as alertness, fatigue, or performance on interpolated tasks. We briefly review trends in risk from the published epidemiological studies that have ensured that the a priori risk was constant. A simple Risk Index based on an additive model is developed on the basis of these trends, and we illustrate how it may be used to assess work schedules. Finally, we compare the results from this Risk Index with those from the UK HSE's Fatigue Index and point out the discrepancies that emerge. We conclude that our risk-based modeling approach may assist in developing safer work schedules and also increase our understanding of this complex, multifaceted area.     

Toward a "Risk Index" to assess work schedules

This article describes our preliminary attempt to develop a Risk Index to estimate the risk of human error on different work schedules based on trends in the relative risk of accidents and injuries, rather than on hypothetical intervening variables such as alertness, fatigue, or performance on interpolated tasks. We briefly review trends in risk from the published epidemiological studies that have ensured that the a priori risk was constant. A simple Risk Index based on an additive model is developed on the basis of these trends, and we illustrate how it may be used to assess work schedules. Finally, we compare the results from this Risk Index with those from the UK HSE's Fatigue Index and point out the discrepancies that emerge. We conclude that our risk-based modeling approach may assist in developing safer work schedules and also increase our understanding of this complex, multifaceted area.     

Diatom assemblages and their relationships to lakewater nitrogen levels and other limnological variables from 36 lakes and ponds on Banks Island,N.W.T., Canadian Arctic

Banks Island, in the Canadian Arctic Archipelago, has been identified as an important reference site for studies of environmental change, especially as it relates to climatic warming. The island is logistically manageable (i.e. researchers can survey the entire island in one field season) and, most importantly, spans three major ecoclimatic regions supporting a diverse and large bird and mammal population. Developing upon earlier work by the authors describing the limnology of Banks Island, this current study: (1) examines which physical and chemical limnological variables influence diatom assemblages in this relatively lush island; and (2) explores variations in the diatom assemblages by ecoclimatic zones. The relationship between diatom taxa from a 36 lake/pond surface sediment calibration set and a suite of limnological variables was explored using multivariate statistics. Dominant diatom species varied based on changing limnological characteristics, particularly between the colder, ultra-oligotrophic lakes in the more northern High Arctic regions compared to the warmer, more nitrogen-rich sites in the Low Arctic regions of Banks Island. Exploration of diatom ecoclimatic and environmental preferences revealed interesting relationships, including the development of a diatom-based transfer function that could be used to track overall trends on lakewater nitrogen concentrations, which may enable future paleolimnological studies to track shifts in nutrient levels and climatic, and other environmental changes. Handling editor: J. Padisak     

Association between shift work and risk of type 2 diabetes mellitus: a systematic review and dose-response meta-analysis of observational studies

ABSTRACT

To evaluate the association between shift work and risk of type 2 diabetes mellitus, we searched PubMed, EMBASE and Web of Science from their inception to June 8, 2019. Observational studies examining the relationship between shift work and type 2 diabetes were included. Subgroup analyses were conducted to explore whether specific characteristics would affect the relationship. A dose-response relationship was estimated by using generalized least squares trend regression. Finally, twelve cohort studies and nine cross-sectional studies were included (inter-rater agreement, k = 0.96). The result of meta-analysis indicated that shift work was associated with an increased risk of type 2 diabetes (relative risk = 1.10, 95% confidence interval = 1.05–1.14). Subgroup analyses demonstrated that female shift workers have increased risk of type 2 diabetes while male not observed, health care workers showed the highest risk compared with civil servants and manual workers, and night shift and rotating shift were associated with an increased risk of type 2 diabetes. Dose-response meta-analysis based on three cohorts among female workers indicated that there might be a positive association between duration of shift work and the risk of type 2 diabetes. In conclusion, shift work is positively associated with an increased risk of type 2 diabetes. Among female workers, with the years of exposure to shift work prolonged, the risk of type 2 diabetes might increase accordingly. In the future, more studies are needed to confirm the results of dose-response analysis.     

Health and safety among film technicians working extended shifts

This paper presents selected results from a pilot research. The study of film technicians' work schedules and occupational hazards was based on a questionnaire administered to all 2200 film technicians (650 valid replies; response rate = 30%), interviews with producers and technicians on film-shooting organization and scheduling, courses in film technique, individual interviews with workers in trade at high risk, and review of the literature on freelancers, on the effects of intermittent work, and on risk factors for musculoskeletal injuries. Work schedules showed a tendency to extremely long work shifts (14 hours per day on average, and up to 19 hours in some trades). Occupational constraints and work schedules were found to relate to an increased risk of work-related injuries. Technicians identified fatigue associated with work schedules as the principal risk of accidents and one of the factors responsible for causing or aggravating their many musculoskeletal injuries. Work schedules were not the only cause of these injuries: stress--due to time constraints, work responsibilities and job insecurity--was also an important risk factor, consistent with the literature on musculoskeletal disorders. Physical workload was also problematic, particularly when demanding tasks had to be performed under severe time constraints.     

Evaluation of Occupational Injuries among Young Workers in West Virginia

We compared workplace injuries between young (16 to 19 years of age) and adult workers using West Virginia Workers' Compensation database. All workers injured between January 1 and December 31, 1995 were included in the analysis. The industry-specific injury incidence rates between young and adults workers were significantly different with lower rates of injury in young workers in all sectors except service sector. In the service sector the young workers had significantly higher injury rates than adults (rate ratios for young workers were 2.28, 1.92, and 2.94 when compared with age groups 20-24, 25-34, and >34, respectively). Estimates of the proportional injury ratio (PIR) indicated significantly greater risk of finger (PIR 1.62) and hand (PIR 1.66) injuries and burns (PIR 3.27) and lacerations (PIR 1.69) in the young workers. The proportion of injuries occurring in the summer months was higher in the young than in the adults (35.2% vs. 27.0%), particularly in the service sector (79.6% vs. 25.9%). Higher injury rates in young workers compared to adults in the service sector may be explained by the seasonal employment of young workers in West Virginia.     

Occupational exposure to mercury vapour on genotoxicity and DNA repair

We have conducted a population study to investigate whether current occupational exposure to mercury can cause genotoxicity and can affect DNA repair efficiency. Blood samples from 25 exposed workers and 50 matched controls were investigated for the expression of genotoxicity. The data indicate that mercury exposure did not cause any significant differences between the workers and controls in the baseline levels of DNA strand breaks (as measured by the alkaline version of the single cell gel electrophoresis [SCGE] assay) or sister chromatid exchanges (SCE). However, the exposure produced elevated average DNA tails length in the SCGE assay and frequency of chromosome aberrations. In the studies, isolated lymphocytes were exposed to 6J/m2 UV-C light or 2 Gy dose of X-rays in a challenge assay and repair of the induced DNA damage was evaluated using the SCGE assay. Results from the UV-light challenge assay showed no difference between the workers and controls in the expression of DNA strand breaks after exposure followed by incubation in the absence or presence of the cellular mitogen (phytohemagglutinin, PHA). No difference in DNA strand breaks between the workers and controls was seen immediately after the X-ray challenge, either. However, significant differences were observed in cells that were incubated for 2h with and without phytohemagglutinin. Data from the X-rays challenge assay were further used to calculate indices that indicate DNA repair efficiency. Results show that the repair efficiencies for the workers (69.7% and 83.9% in un-stimulated and stimulated lymphocytes, respectively) were significantly lower than that of matched controls (85.7% and 90.4%, respectively). In addition, the repair efficiency showed a consistent and significant decrease with the duration of occupational exposure to mercury (from 75.7% for <10 years employment, to 65.1% for 11-20 years and to 64.1% for 21-35 years) associated with increase of cytogenetic damage. Our study suggests that the occupational exposure to mercury did not cause a direct genotoxicity but caused significant deficiency in DNA repair. Our observations are consistent with previous studies using the standard chromosome aberration assay to show that exposure to hazardous environmental agents can cause deficiency in DNA repair. Therefore, these affected individuals may have exposure-related increase of health risk from continued exposure and in combination with exposure to other genotoxic agents.     

Metabolic Syndrome in Permanent Night Workers

Night and shift work might be risk factors for metabolic and cardiovascular disorders due to interference with diet, circadian metabolic rhythms, and lifestyle. The relationship between permanent night work and metabolic and cardiovascular risk factors was explored in a retrospective longitudinal study of workers employed in a large municipal enterprise in charge of street cleaning and domestic waste collection. All subjects who had worked night shifts between 1976 and 2007 as hand sweepers, motor sweepers, and delivery tricar drivers were compared with subjects who always worked the same jobs but on day shifts. From the periodical medical surveillance files, we identified 488 male workers who had been examined on average five times (minimum 2, maximum 14) during the study period, for a total of 2,328 medical examinations; 157 always had worked day shifts, 12 always the night shift, and 319 both (initially day and subsequently night shifts). Their age ranged from 22 to 62 yrs, and work experience varied from 1 to 28 yrs. Lifestyle habits (smoking, alcohol consumption), body mass index, serum glucose, total cholesterol, tryglicerides, hepatic enzymes, blood pressure, resting electrocardiogram, diabetes, coronary heart disease, hypertension, and related drugs were taken into consideration for the analysis. We used generalized estimating equations (GEE) models (exchangeable correlation matrix) to analyze the relationship between night work and health effects while accounting for within‐subject correlations and adjusting for study period, job, age, and lifestyle variables. As a whole, night workers smoked more and had significantly higher BMI, serum total cholesterol, and triglycerides than day workers. Both the inter‐individual comparison between day and night workers and the intra‐individual comparison among the workers, who were day workers at the beginning of their employment and later became night workers, showed a significant increase in BMI, total cholesterol, and tryglicerides associated with night work. No consistent effect was seen on fasting glucose, hepatic enzymes, and blood pressure, whereas a higher incidence of coronary heart disease was recorded in night workers.     

Quantitative biomechanical workplace exposure measures: Distribution centers

Physical work exposure characteristics assessed in most previous epidemiologic studies have been described mostly in gross categorical terms (e.g. heavy work, lifting and forceful movements, etc.) and have resulted in relatively moderate associations with low back pain risk. We hypothesized that it was necessary to characterize work demands in a much more quantitative fashion so that the precise biomechanically meaningful measures of exposure were available for risk analysis. In this study, we used sophisticated instrumentation to continuously document 390 physical exposures during lifting (in four types of distribution centers) throughout work. This study profiles these exposures and shows how these exposures vary as a function of the type of distribution center and compares the exposures to (previously documented) manufacturing exposures. Static load and load moment measures were found to greatly under-represent true (dynamic) load and load moment exposures to workers. Lift durations averaged 11–12% of the cycle time in distribution environments. This study indicates that distribution workers are commonly exposed to greater extreme loads and move much more rapidly than manufacturing employees. The information provided here can serve as a basis for low back pain risk assessments.     

How dangerous are falls in old people at home?

From a survey in six general practices information was obtained on 125 people aged 65 and over who fell in their own homes. Three fractured their femurs and 15 had other fractures; most of the rest suffered only trivial injuries. Twenty lay on the floor for more than one hour; none were known to have suffered hypothermia. One-quarter of these patients died within one year of the fall, five times as many as in an age- and sex-matched control group; while of those who lay on the floor for more than one hour, half died within six months of the fall. Factors associated with mortality from falls were impaired mobility, abnormal balance, and a disturbed pattern of gait. Falls at home in old age are often indicative of the presence of severe ill health.     

Horse riding in urban conservation areas: Reviewing scientific evidence to guide management

Summary We undertook a literature review of the impacts of horse riding in conservation areas, and used it to guide management of horse riding in Canberra Nature Park (CNP), a large, fragmented semi‐natural park in and around the city of Canberra in the Australian Capital Territory. The literature review established that, because of their relatively large weight and small area in contact with the ground, horses have a relatively high potential for doing environmental damage. Impacts tend to be generally lowest for hikers, followed by motorcycles, horses and four‐wheeled vehicles. One study showed horse traffic caused more damage on established trails than motorcycles, off‐road bicycles or hikers. Most published studies of horse‐riding impacts in Australia have been conducted in alpine and subalpine environments, and in temperate woodlands and forests on sandstone near Sydney. They have shown that impacts are generally highest in previously untracked areas. Impacts on established trails are generally most marked on sections of trail that are wet, boggy or steep, and on unplanned and unmaintained trails. Impacts are lowest on constructed and maintained trails. Trail proliferation, associated with avoidance of untrafficable sections and short‐cutting, can be a major problem. Horses also have potential to spread weeds, because pastures and dried stock feeds contain large numbers of weed seeds that retain high levels of viability in horse manure. The risk of weed establishment is highest when manure is deposited in disturbed, damp sites, particularly when riding off‐track. Much less weed establishment is apparent when horse riders remain on‐track. Horse riding is a popular activity, but one that is relatively expensive to provide for, and one that may reduce opportunities for lower‐impact recreational park users. For all these reasons it appears socially equitable that provision is made for lower numbers of horse riders compared to numbers of park users involved in lower impact, more passive, recreational activities. We conclude by describing how this information was used to develop principles to guide management of horse riding and assess risk at individual sites in Canberra Nature Park.