Reducing sickness absence among public-sector healthcare employees: the difference-making roles of managerial and employee participation

PURPOSE

Evaluations of organizational-level interventions to prevent work-related illness have identified enabling factors, but knowledge of necessary and sufficient conditions for intervention success is needed. The aim was to identify difference-making factors that distinguish intervention groups with and without a positive intervention effect on sickness absence.

METHODS

An organizational-level intervention designed to decrease sickness absence by providing support from process facilitators was implemented at eight healthcare workplaces in Sweden between 2017 and 2018. We applied coincidence analysis (CNA) to analyze 34 factors and determine which factors were necessary and sufficient for a successful implementation of tailored interventional measures on an organizational level (dichotomous) and reduced sickness absence (trichotomous).

RESULTS

Two factors perfectly explained both the presence and absence of a successful implementation: "a high sense of urgency" and "good anchoring and participation from the strategic management". The presence of either of these factors alone was sufficient for successful implementation, whereas the joint absence of both conditions was necessary and sufficient for the absence of successful implementation and an intervention effect. In addition, high employee participation was both necessary and sufficient for a high intervention effect. For organizations without high employee participation, successful implementation led to a medium-effect size.

CONCLUSIONS

This study identified participation as a difference-maker in the implementation process. Participation from different stakeholders turned out to be important in different phases. When implementing organizational-level interventions, high participation from both strategic management and employees appears to be crucial in terms of the intervention's effect on sickness absence.

The COPE Staff study: Study description and initial report regarding job satisfaction, work-life conflicts, stress, and burnout among Swedish maternal and neonatal healthcare workers during the COVID-19 pandemic

OBJECTIVE

To describe the study design of the COPE Staff cohort study on working conditions for maternal and neonatal healthcare workers (MNHCWs), and present baseline data regarding job satisfaction, work-life conflicts, stress, and burnout.

METHODS

Between January and April 2021, 957 MNHCWs (administrative and medical staff) completed a baseline survey. Average levels of job satisfaction, work-life conflicts, stress, and burnout, and associations to perceived workload were assessed.

RESULTS

The average levels of job satisfaction, work-life conflicts, stress, and burnout were 68.6 (95% confidence interval [CI] 64.3-72.8), 42.6 (95% CI 37.3-48.0), 42.0 (95% CI 37.7-46.3), and 1.9 (95% CI 1.6-2.2), respectively. The respondents scoring above critical values indicating clinical burnout ranged between 3% and 18%, respectively, for the four burnout sub-dimensions. Women reported significantly higher levels of stress and burnout. Younger participants had lower job satisfaction and higher levels of work-life conflicts, stress, and burnout. Higher perceived workload was significantly associated with lower job satisfaction levels and higher levels of work-life conflicts, stress, and burnout.

CONCLUSIONS

Our results indicate associations between MNHCWs perceived workload and job satisfaction, work-life conflicts, stress, and burnout during the COVID-19 pandemic. Eighteen percent scored above critical values for exhaustion.

Shifting from an individual to an organizational perspective in work environment management - a process evaluation of a six-year intervention program within the Swedish public sector

BACKGROUND

Working systematically with the work environment, particularly the organizational and psychosocial work environment entails several challenges for employers. There is a lack of knowledge on how to best undertake this work. Thus, the aim of this study is to evaluate the process of a six-year organizational-level intervention program where workplaces could apply for additional funds to implement preventive intervention measures, with the intention of improving working conditions and reducing sickness absence within the Swedish public sector.

METHODS

The program management process was studied using a mixed-method approach combining qualitative document and content analyses based on process documentation produced between 2017 and 2022 (n = 135), interviews with internal occupational health services professionals in 2021 (n = 9) and quantitative descriptive analyses of submitted applications with decisions from 2017 to 2022 (n = 621).

RESULTS

Qualitative analyses of the process documentation revealed concerns from the project group regarding access to sufficient competence and resources among stakeholders and participating workplaces, and role conflicts and ambiguities between the program and everyday operations. To address these challenges, the application process was developed over time using the knowledge gained from previous years. A change in the mental models in work environment management, from an individual to an organizational perspective, was seen among the project group and the internal occupational health services responsible for implementing most of the granted intervention measures. In addition, the proportion of granted intervention measures on an organizational level increased throughout the years from 39% in 2017 to 89% in 2022. The changes in the application process were believed to be the main contributor to the change among the applying workplaces.

CONCLUSIONS

Results indicate that a long-term organizational-level workplace intervention program may be used, by the employer, as a tool for shifting from an individual- to an organizational perspective in the work environment management. However, additional measures on multiple levels need to be implemented to secure a sustainable shift in perspective within the organization.

Working conditions for healthcare workers at a Swedish university hospital infectious disease department during the COVID-19 pandemic: barriers and facilitators to maintaining employee wellbeing

Background

Healthcare workers (HCWs) at infectious disease departments have held the frontline during the COVID-19 pandemic. This study aimed to identify barriers and facilitators to maintaining the employees' wellbeing that may be used to increase preparedness for future pandemics within ID Departments.

Methods

In September 2020, a web-based survey on demographics and work environment was distributed to all HCWs at the Infectious Disease Department at Sahlgrenska University Hospital. Results were compared with a pre-COVID-19 survey from October 2019. A quantitative analysis of the overall effects of the pandemic on the working conditions of HCWs was conducted; in addition, a qualitative content analysis of open-ended responses was performed.

Results

In total, 222 and 149 HCWs completed the pre-COVID-19 and COVID-19 surveys (84 and 54% response rate), respectively. Overall, we found significant changes regarding increased workload, lack of emotional support in stressful work situations, and inability to recover after shifts. These factors correlated both with younger age and concern of becoming infected. The open-ended answers (n = 103, 69%) revealed five generic categories (Workload; Organizational support; Worry and ethical stress; Capability; and Cooperation and unity) with a total of 14 identified factors representing plausible individual and organizational-level barriers or facilitators to sustained employee wellbeing.

Conclusion

Younger HCWs as well as those expressing worries about contracting the infection were found to be particularly affected during the COVID-19 pandemic and these groups may require additional support in future outbreaks. Factors both increasing and decreasing the pandemic-induced negative health consequences for HCWs were identified; this knowledge may be utilized in the future.

Under pressure - The working situation of Swedish healthcare managers during the first wave of COVID-19

Introduction

The aim of this study is to provide insight into the psychosocial work situation of hospital managers during the first wave of the COVID-19 pandemic.

Methods

Mixed-effect modelling was used on survey data on job demands, job resources, job motivation, and work-life balance among over 500 managers working in 55 departments of a large Swedish university hospital in 2019 and 2020. Responses from 6011 employees were then used to stratify the analysis for COVID-19 exposure. Inductive content analysis was applied to open-ended questions on the managers' views on organisational prerequisites during the onset of the pandemic.

Results

The proportion of managers reporting difficulties with role clarity, quantitative demands, decision-making authority, and emotional support, time for recovery at work, motivation deficits, or problems with work-life balance clearly increased during the first wave of the pandemic. The proportion of managers reporting negative responses was higher in departments with high COVID-19 exposure. The qualitative analysis shows that overall governance in terms of clear, fair, and well-communicated routines, resource allocation, and division of responsibilities constituted an important framework for managerial during the crisis. First-line managers also require a mandate to re-organize their roles and their teams to successfully adapt to the situation. Organisational and social support was also important resources.

Discussion

This is the first study investigating healthcare managers' work situation during the first wave of the COVID-19 pandemic in a Swedish context. As expected, it indicates an increasingly strained work situation during the crisis, but it also provides findings on organisational prerequisites that allow healthcare managers to cope with stressful situations. In line with previous research on organisational resilience, the study provides suggestions for how higher-level managers can act in order to provide front-line managers with the organisational prerequisites they need to adapt, learn and develop successfully during times of unpredictability, insecurity, and rapid change in order to offer the best possible support to health care workers.

Challenges imposed by the COVID-19 pandemic on the Obstetrics and Gynecology residency program: a mixed-methods Swedish survey in the COPE Staff cohort study

BACKGROUND

To outline how the training program and work situation of residents in Obstetrics and Gynecology (OB-GYN) was affected by the pandemic and to illuminate how residents experienced these changes.

METHODS

As part of the COVID-19 in Pregnancy and Early Childhood Staff (COPE Staff) cohort study, between January and May 2021, all participating residents were invited to answer a 28-question online Resident Survey focusing on their specialist education, work situation and experiences during the COVID-19 pandemic. Descriptive statistics were given in percentages for categorical variables and means and standard deviations (SD) for continuous variables. Univariate comparative analyses were performed with the use of the Pearson's Chi-2-test for dichotomous data. The association between residents' worry about the quality and length of their specialist training, with extra clinical hours and transfer to other healthcare institutions were assessed by multivariate logistic regression. Free text responses were analyzed by content analysis.

RESULTS

Of the 162 participating OB-GYN residents, 69% expressed concern that the pandemic would have a negative impact on their training. Ninety-five (95%) reported cancellation/postponement of educational activities, 70% performed fewer surgeries and 27% had been transferred to other healthcare institutions where about half reported having gained more general knowledge as a physician. Working extra clinical hours was reported by 69% (7.4 ± 5.3 hours per week) and 14% had considered changing their profession due to the pandemic. Senior residents, compared to junior residents, more often experienced cancelled/postponed clinical rotations (30% vs 15%, P=0.02) and reported performing fewer surgeries (P=0.02). The qualitative analysis highlighted the lack of surgical procedural training as a major concern for residents.

CONCLUSION

The COVID-19 pandemic has strongly impacted the training program and work situation of OB-GYN residents in Sweden. Residents were concerned over the negative impact of the pandemic on their training program and senior residents reported more missed educational opportunities as compared to junior residents. Program directors, head of institutions and clinical supervisors can use the problem areas pinpointed by this study to support residents and compensate for missed educational opportunities. While hands-on-training and operating time cannot be compensated for, the authors hope that the findings of the study can help develop new strategies to minimize the negative impact of the current and future pandemics on resident education and work situation.

Working conditions for hospital-based maternity and neonatal health care workers during extraordinary situations - A pre-/post COVID-19 pandemic analysis and lessons learned

Objective

The aim of this study was to investigate how the changed work routines during the COVID-19 pandemic has been affecting the working environment for hospital-based maternity and neonatal health care workers, and to identify preventive measures to be used in future situations when health care organizations are under pressure.

Methods

All maternity and neonatal health care workers in a Swedish university hospital were surveyed during October 2019 and September 2020. The data was analyzed by document analysis of implemented changes in working routines, a quantitative analysis of the overall effects on the working conditions, and a qualitative analysis of open-ended responses.

Results

A total of 660 maternity and neonatal health care workers completed the pre-COVID-19 survey (74% response rate) and 382 the COVID-19 survey (35% response rate). Lack of personal protective equipment, worry about becoming infected, uncertainty whether implemented changes were enough, and challenges in communicating updated routines had negative effects on maternity and neonatal health care workers’ working conditions. Team spirit and feeling valued by peers had a positive effect.

Conclusions

Results suggest that negative effects on maternity and neonatal health care workers’ health can partly be prevented in future critical situations by creating a work climate that acknowledges the employees’ worry about being infected, securing adequate pre-conditions for managers, creating a strong psychosocial safety climate and systematically improving the working conditions for the maternity and neonatal health care workers, as well as maintaining the positive perceived effects of increased team spirit and feeling valued by peers.

Multilevel, risk group-oriented strategies to decrease sickness absence in the public sector: evaluation of interventions in two regions in Sweden

Purpose

Sickness absence has been identified as needing to be addressed through multilevel interventions, but knowledge regarding optimal design and implementation of such interventions is scarce. The aim of this study was to evaluate the implementation and effects of a large-scale multilevel intervention in the public sector in Sweden.

Methods

The overall effect of the intervention was assessed using mixed-effect models. Sickness absence data (before, and 6 or 12 months after the intervention) for 90 intervention groups and 378 reference groups was retrieved from administrative personnel systems from the two participating regional councils. The implementation processes were evaluated using qualitative content analysis of qualitative interviews conducted at two timepoints.

Results

The results show that the vast majority of implemented measures were on an individual level and the integration of the intervention differed between the two regions. The reception and perception of the intervention activities seem to have been influenced by the implementation process, and how well the interventions were communicated and integrated, both regarding the integration of the different interventions and their integration into the discrete context and existing routines. No short-term overall effects on sickness absence were found.

Conclusions

The results point to the many challenges in implementing complex interventions, especially where organizational measures are involved—including adequate participation by, and communication between, the involved actors, as well as sufficient resources. The results indicate potential learning effects regarding the awareness of organizational factors in sick leave, after implementing and integrating multilevel strategies.

Process facilitators shifting between the support and expert roles in a complex work environment intervention in the Swedish healthcare sector

PURPOSE

Process facilitation as part of a complex intervention for changing or improving practices within workplaces is becoming a common work method. The aim of this study was to investigate what characterizes the process-facilitating role in a complex intervention.

DESIGN/METHODOLOGY/APPROACH

The present study focuses on a complex work environment intervention targeting eight organizational units (workplaces) in the Swedish healthcare sector. The study applies a mixed-method approach and has been carried out in two steps. First, a qualitative process evaluation was performed. Secondly, an evaluation was conducted to see to what extent these identified conditions and mechanisms affected the quantitative intervention effect in term of sickness absence.

FINDINGS

The analysis shows that the facilitating role consisted of three overlapping and partially iterative phases. These phases involved different activities for the facilitating role. Depending on how the facilitating role and the intervention were designed, various supporting conditions were found to significantly affect the outcome of the intervention measured as the total sickness absence.

RESEARCH LIMITATIONS/IMPLICATIONS

It is concluded that the facilitation is not static or fixed during the change process. Instead, the facilitation role develops and emerges through the process of support during the different implementation phases.

PRACTICAL IMPLICATIONS

The facilitative role of performing support is based on a combination of support role activities and expert role activities. The support role focuses on support activities, while the expert role includes capacity building through knowledge- and legitimacy-oriented activities.

ORIGINALITY/VALUE

This study contributes to earlier research by developing a methodological approach for carrying out process facilitation in complex interventions.

Methodological approach for measuring the effects of organisational-level interventions on employee withdrawal behaviour

Background

Theoretical frameworks have recommended organisational-level interventions to decrease employee withdrawal behaviours such as sickness absence and employee turnover. However, evaluation of such interventions has produced inconclusive results. The aim of this study was to investigate if mixed-effects models in combination with time series analysis, process evaluation, and reference group comparisons could be used for evaluating the effects of an organisational-level intervention on employee withdrawal behaviour.

Methods

Monthly data on employee withdrawal behaviours (sickness absence, employee turnover, employment rate, and unpaid leave) were collected for 58 consecutive months (before and after the intervention) for intervention and reference groups. In total, eight intervention groups with a total of 1600 employees participated in the intervention. Process evaluation data were collected by process facilitators from the intervention team. Overall intervention effects were assessed using mixed-effects models with an AR (1) covariance structure for the repeated measurements and time as fixed effect. Intervention effects for each intervention group were assessed using time series analysis. Finally, results were compared descriptively with data from process evaluation and reference groups to disentangle the organisational-level intervention effects from other simultaneous effects.

Results

All measures of employee withdrawal behaviour indicated statistically significant time trends and seasonal variability. Applying these methods to an organisational-level intervention resulted in an overall decrease in employee withdrawal behaviour. Meanwhile, the intervention effects varied greatly between intervention groups, highlighting the need to perform analyses at multiple levels to obtain a full understanding. Results also indicated that possible delayed intervention effects must be considered and that data from process evaluation and reference group comparisons were vital for disentangling the intervention effects from other simultaneous effects.

Conclusions

When analysing the effects of an intervention, time trends, seasonal variability, and other changes in the work environment must be considered. The use of mixed-effects models in combination with time series analysis, process evaluation, and reference groups is a promising way to improve the evaluation of organisational-level interventions that can easily be adopted by others.

Can Working Conditions and Employees' Mental Health Be Improved via Job Stress Interventions Designed and Implemented by Line Managers and Human Resources on an Operational Level?

Organisational-level interventions are recommended for decreasing sickness absence, but knowledge of the optimal design and implementation of such interventions is scarce. We collected data on working conditions, motivation, health, employee turnover, and sickness absence among participants in a large-scale organisational-level intervention comprising measures designed and implemented by line managers and their human resources partners (i.e., operational-level). Information regarding the process, including the implementation of measures, was retrieved from a separate process evaluation, and the intervention effects were investigated using mixed-effects models. Data from reference groups were used to separate the intervention effect from the effects of other concurrent changes at the workplace. Overall, working conditions and motivation improved during the study for both the intervention and reference groups, but an intervention effect was only seen for two of 13 evaluated survey items: clearness of objectives (p = 0.02) and motivation (p = 0.06). No changes were seen in employees' perceived health, and there were no overall intervention effects on employee turnover or sickness absence. When using operational-level workplace interventions to improve working conditions and employees' health, efforts must be made to achieve a high measure-to-challenge correspondence; that is, the implemented measures must be a good match to the problems that they are intended to address.

Process Evaluation of an Operational-Level Job Stress Intervention Aimed at Decreasing Sickness Absence among Public Sector Employees in Sweden

Work-related sickness absence carries large societal costs, and interventions aimed at decreasing sickness absence need to be performed in an effective way. This study evaluated the implementation process of an operational-level job stress intervention, implemented between 2017 and 2018 in the public sector, by assessing the extent to which the allocated resources reached the intended target group, if the planned measures could be expected to address the relevant work environmental challenges, and if the planned measures were implemented. Data were collected from applications for funding in the intervention (n = 154), structured interviews (n = 20), and register data on sickness absence (n = 2912) and working conditions (n = 1477). Thematic analysis was used to classify the level of the work environmental challenges, the level and perspective of the suggested measures, and the "measure-to-challenge correspondence". Overall, participating workplaces (n = 71) had both higher sickness absence (p = 0.01) and worse reported working conditions compared to their corresponding reference groups. A measure-to-challenge correspondence was seen in 42% of the measures, and individual-level measures were mostly suggested for organisational-level work environment challenges. Almost all planned measures (94%) were ultimately implemented. When performing operational-level interventions, managers and their human resource partners need support in designing measures that address the work environmental challenges at their workplace.

A Survey of Psychiatric Healthcare Workers' Perception of Working Environment and Possibility to Recover Before and After the First Wave of COVID-19 in Sweden

Objective: This study aimed to investigate the impact of the first wave of the COVID-19 pandemic on perceived working environment, including the possibility to recover, among psychiatric healthcare workers (PHCWs) in comparison with pre-pandemic measures. Method: A link to an anonymous, web-based COVID-19 related survey was sent via email to all PHCWs at a university hospital in Sweden (n = 1,618) in September 2020. The response rate was 38% (566 of 1,507 eligible participants). Working environment survey responses collected in 2019 were used as pre-pandemic comparators. Statistical analyses were performed to assess overall impact over time on work demands, support, motivation, and recovery, stratified by professional role, and considering variables such as access to personal protective equipment. Results: The percentage of individuals responding negatively to statements about working environment increased significantly for most items after the first wave. Similarly, the increase of five of the investigated factors indicated a more negative perception of recovery during the pandemic. Registered nurses reported a greater negative impact of the pandemic on perceived working conditions and ability to recover than other professional groups. PHCWs working with patients with COVID-19 (35%) who reported being worried about becoming infected (12%) or infecting others (17%), or lacking adequate personal protective equipment (22%) were more negatively impacted regarding work environment-related items than those who did not. Conclusions: PHCWs' working environment and possibility for recovery were impacted by the first wave of the COVID-19 pandemic, nurses being most affected. Although psychiatric services do not directly care for patients with severe COVID-19 infection, the results from this study suggests that mental health services should also prepare for future pandemics.

Low personal exposure to benzene and 1,3-butadiene in the Swedish petroleum refinery industry

PURPOSE

Petroleum refinery workers are exposed to the carcinogens benzene and 1,3-butadiene. Declining exposures have been reported internationally but information on current exposure in the Swedish refinery industry is limited. The aim was to examine refinery workers' personal exposure to benzene and 1,3-butadiene and increase awareness of exposure conditions by collaboration with involved refineries.

METHODS

Altogether 505 repeated personal exposure measurements were performed among workers at two refineries. Full-shift measurements were conducted in different exposure groups using Perkin Elmer diffusive samplers filled with Carbopack X. Mean levels were calculated using mixed-effects models. A large fraction of measurements below the limit of detection (LOD) required imputation of computer-generated data.

RESULTS

Mean benzene exposure among process technicians was 15.3 µg/m3 (95% CI 10.4-22.5 µg/m3) and 13.7 µg/m3 (95% CI 8.3-22.7 µg/m3) for Refinery 1 and 2, respectively. Process technicians working outdoors had higher exposure than maintenance workers (20.7 versus 5.9 µg/m3, p < 0.01). Working in the harbour and tank park (Refinery 1), compared with the process area, was associated with higher exposure. The 1,3-butadiene exposure was low, 5.4 and 1.8 µg/m3, respectively. The total variation was generally attributed to within-worker variability.

CONCLUSIONS

Low benzene and 1,3-butadiene levels were found among refinery workers. Mean benzene exposure was about 1% of the Swedish occupational limit (1500 µg/m3) and for 1,3-butadiene, exposure was even lower. A large fraction of values below the LOD can be managed by carefully modelled, computer-generated data.

Personal exposure to benzene and 1,3-butadiene during petroleum refinery turnarounds and work in the oil harbour

Purpose

Petroleum refinery workers’ exposure to the carcinogens benzene and 1,3-butadiene has decreased during normal operations. However, certain occupational groups or events at the refineries still involve a risk of higher exposures. The aim of this study was to examine the personal exposure to benzene and 1,3-butadiene at refinery turnarounds and during work in the oil harbour.

Methods

Personal exposure measurements of benzene and 1,3-butadiene were taken during work shifts, with a priori assumed higher benzene exposure, using PerkinElmer diffusive samplers filled with Carbopack X. Mean exposure levels were calculated, and repeated exposure measurements, when available, were assessed using mixed effect models. Group and individual compliance with the Swedish occupational exposure limit (OEL) was tested for the different exposure groups.

Results

Mean benzene exposure levels for refinery workers during the three measured turnarounds were 150, 610 and 960 µg/m³, and mean exposures for oil harbour workers and sewage tanker drivers were 310 and 360 µg/m³, respectively. Higher exposures were associated with handling benzene-rich products. Most occupational groups did not comply with the Swedish OEL for benzene nor did the individuals within the groups. The exposure to 1,3-butadiene was very low, between <1 and 3 % of the Swedish OEL.

Conclusions

Work within the petroleum refinery industry, with potential exposure to open product streams containing higher fractions of benzene, pose a risk of personal benzene exposures exceeding the OEL. Refinery workers performing these work tasks frequently, such as contractors, sewage tanker drivers and oil harbour workers, need to be identified and protected.

Urinary albumin excretion in healthy adults: a cross sectional study of 24-hour versus timed overnight samples and impact of GFR and other personal characteristics

Background

Urinary albumin can be measured in 24 h or spot samples. The 24 h urinary albumin excretion rate is considered the gold standard, but is cumbersome to collect. Instead, often an overnight sample is collected, and adjusted for dilution. Proxies for 24 h excretion rate have been studied in diabetics, but seldom in healthy individuals. Our aims were to compare 24 h and overnight albumin excretion, to assess the impact of personal characteristics, and to examine correlations between the 24 h excretion rate and proxies such as the albumin to creatinine ratio (ACR).

Methods

Separate 24 h and overnight urine samples were collected from 152 healthy kidney donors. Urinary creatinine, specific gravity, collection time, and sample volume determined. Differences between 24 h and overnight samples were examined, and the effects of age, sex, smoking, body mass, glomerular filtration rate, and urinary flow rate were assessed.

Results

The 24 h albumin excretion rate and ACR were both significantly higher than their overnight counterparts. Unadjusted albumin was unsurprisingly higher in the more concentrated overnight samples, while concentrations adjusted for specific gravity were similar. In multivariate analysis, the 24 h excretion rate and proxies were positively associated with glomerular filtration rate, as was ACR in overnight samples. There were positive associations between urinary albumin and body mass.

Conclusions

Proxies for the 24 h albumin excretion rate showed relatively high correlations with this gold standard, but differences due to sampling period, adjustment method, and personal characteristics were large enough to be worth considering in studies of albumin excretion in healthy individuals.

Physiologically-based toxicokinetic model for cadmium using Markov-chain Monte Carlo analysis of concentrations in blood, urine, and kidney cortex from living kidney donors

The health effects of low-level chronic exposure to cadmium are increasingly recognized. To improve the risk assessment, it is essential to know the relation between cadmium intake, body burden, and biomarker levels of cadmium. We combined a physiologically-based toxicokinetic (PBTK) model for cadmium with a data set from healthy kidney donors to re-estimate the model parameters and to test the effects of gender and serum ferritin on systemic uptake. Cadmium levels in whole blood, blood plasma, kidney cortex, and urinary excretion from 82 men and women were used to calculate posterior distributions for model parameters using Markov-chain Monte Carlo analysis. For never- and ever-smokers combined, the daily systemic uptake was estimated at 0.0063 μg cadmium/kg body weight in men, with 35% increased uptake in women and a daily uptake of 1.2 μg for each pack-year per calendar year of smoking. The rate of urinary excretion from cadmium accumulated in the kidney was estimated at 0.000042 day(-1), corresponding to a half-life of 45 years in the kidneys. We have provided an improved model of cadmium kinetics. As the new parameter estimates derive from a single study with measurements in several compartments in each individual, these new estimates are likely to be more accurate than the previous ones where the data used originated from unrelated data sets. The estimated urinary excretion of cadmium accumulated in the kidneys was much lower than previous estimates, neglecting this finding may result in a marked under-prediction of the true kidney burden.

Variability of urinary cadmium excretion in spot urine samples, first morning voids, and 24 h urine in a healthy non-smoking population: implications for study design

When selecting the least biased exposure surrogate, for example, the concentration of a biomarker in a urine sample, information on variability must be taken into consideration. We used mixed-effects models to estimate the variability and determinants of urinary cadmium (U-Cd) excretion using spot urine samples collected at six fixed times during 2 days about 1 week apart, from 24 healthy non-smokers. The urine samples were analysed for U-Cd, the concentrations were adjusted for dilution, and the excretion rates were calculated. Between-individual variability dominated the total variability for most measures of U-Cd excretion, especially for 24 h urine and first morning samples. The U-Cd excretion showed a circadian rhythm during the day, and time point of sampling was a significant factor in the mixed-effects models, thus a standardised sampling time, such as first morning urine samples, needs to be applied. Gender, urinary flow rate, age, and urinary protein excretions were also significant determinants for U-Cd excretion. The choice of biomarker for U-Cd excretion was found to be more important in individually-based studies of exposure-response relationships than in studies of comparing Cd levels of groups. When planning a study, this variability of U-Cd in spot samples must be acknowledged.

The relationship between cadmium in kidney and cadmium in urine and blood in an environmentally exposed population

INTRODUCTION

Cadmium (Cd) is toxic to the kidney and a major part of the body burden occurs here. Cd in urine (U-Cd) and blood (B-Cd) are widely-used biomarkers for assessing Cd exposure or body burden. However, empirical general population data on the relationship between Cd in kidney (K-Cd), urine, and blood are scarce. Our objectives were to determine the relationship between cadmium in kidney, urine, and blood, and calculate the elimination half-time of Cd from the kidney.

METHODS

Kidney cortex biopsies, urine, and blood samples were collected from 109 living kidney donors. Cd concentrations were determined and the relationships between K-Cd, U-Cd, and B-Cd were investigated in regression models. The half-time of K-Cd was estimated from the elimination constant.

RESULTS

There was a strong association between K-Cd and U-Cd adjusted for creatinine (rp=0.70, p<0.001), while the association with B-Cd was weaker (rp=0.44, p<0.001). The relationship between K-Cd and U-Cd was nonlinear, with slower elimination of Cd at high K-Cd. Estimates of the K-Cd half-time varied between 18 and 44years. A K-Cd of 25μg/g corresponds to U-Cd of 0.42μg/g creatinine in overnight urine (U-Cd/K-Cd ratio: about 1:60). Multivariate models showed Cd in blood and urinary albumin as determinants for U-Cd excretion.

DISCUSSION

In healthy individuals with low-level Cd exposure, there was a strong correlation between Cd in kidney and urine, especially after adjustment for creatinine. Urinary Cd was also affected by Cd in blood and urinary albumin. Previous estimates of the U-Cd/K-Cd ratio may underestimate K-Cd at low U-Cd.

Associations between urinary excretion of cadmium and proteins in a nonsmoking population: renal toxicity or normal physiology?

BACKGROUND

Associations between cadmium (Cd) and kidney function have been reported even at low levels of exposure in the general population. Recently, the causality of these associations has been questioned.

OBJECTIVES

We examined associations between urinary Cd (U-Cd; a biomarker of exposure) and urinary proteins that are used as biomarkers of kidney effects, based on repeated short-term sampling in healthy subjects.

METHODS

Twenty-four hour urine samples were collected on 2 separate days at six fixed times from 30 healthy nonsmoking men and women (median age 39 years). We analyzed the samples (N = 354) for Cd (i.e., U-Cd) and two proteins used as kidney function biomarkers: urinary albumin (U-Alb) and alpha-1-microglobulin (U-A1M). Concentrations were adjusted for creatinine concentration or for specific gravity, and excretion rates (mass per hour) were calculated. Possible associations were assessed within each individual participant, and mean correlations and regressions were evaluated.

RESULTS

We found clear positive mean associations within individuals between the excretion of U-Cd [mean, 0.11 µg/g creatinine (range, 0.01-0.52 µg/g creatinine)] and both U-Alb and U-A1M. The associations were stronger for excretion rates and concentrations adjusted for specific gravity than for concentrations adjusted for creatinine. We also found significant positive associations of urinary flow with excretion of U-Cd, U-Alb, and U-A1M.

CONCLUSIONS

Associations between short-term changes in U-Cd and markers of kidney function within individual nonsmoking study participants are unlikely to reflect effects of Cd toxicity. A more likely explanation is that these associations result from normal variation in renal function, including changes in urinary flow, that influence the urinary excretion of both Cd and proteins in the same direction. These effects of normal variability may result in overestimation of the adverse effects of Cd on kidney function at low-level Cd exposure.

Sampling of urinary cadmium: differences between 24-h urine and overnight spot urine sampling, and impact of adjustment for dilution

PURPOSE

Urinary cadmium (U-Cd) sampling can be done either by 24-h urine or spot urine sampling, and adjustment for dilution is usually needed. The choice of sampling period and adjustment technique could, however, potentially induce bias. The aim of the study was to compare 24-h urine and spot urine sampling and two dilution adjustment techniques, when assessing U-Cd.

METHODS

Separate 24-h urine (U24) and timed overnight spot urine (UON) samples were collected from 152 healthy kidney donors. U-Cd, creatinine concentration (U-Crea) and specific gravity (SG) were analysed. Differences between U24 and UON samples were tested using paired t test, and the effect of urinary flow rate (UF) was assessed by linear regression.

RESULTS

The cadmium excretion rate (U-Cd/h) was lower in the UON than in U24 samples (mean 0.017 μg/h vs. 0.021 μg/h; p < 0.001). This decrease was found also for the creatinine-adjusted U-Cd (U-CdCrea) (mean 0.36 μg/gC and 0.41 μg/gC; p < 0.001). For U-Cd adjusted for specific gravity (U-CdSG), the difference was reversed, but not statistically significant. The creatinine excretion rate (U-Crea/h) decreased at low UF, especially in the UON.

CONCLUSIONS

Since U-Cd/h was lower in UON than in U24 samples, the former will underestimate the true Cd excretion. This was seen for U-CdCrea but not for U-CdSG. However, it may be an advantage that the U-CdSG is similar, irrespective of sampling strategy. At low UF, U-CdCrea will be biased upwards. Whether U24 or UON samples adjusted for U-Crea or SG best reflect kidney-Cd is still unknown.