Interaction between Shift Work and Established Coronary Risk Factors.

BACKGROUND: Shift work is associated with increased risk of cardiovascular disease, but the causes have not yet been fully established. It has been proposed that the coronary risk factors are more hazardous for shift workers, resulting in a potential interaction effect with shift work. OBJECTIVE: To analyse interaction effects of work schedule and established risk factors for coronary artery disease on the risk of myocardial infarction. METHODS: This analysis was conducted in SHEEP/VHEEP, a case-control study conducted in two counties in Sweden, comprising all first-time cases of myocardial infarction among men and women 45-70 years of age with controls stratified by sex, age, and hospital catchment area, totalling to 4648 participants. Synergy index (SI) was used as the main outcome analysis method for interaction analysis. RESULTS: There was an interaction effect between shift work and physical inactivity on the risk of myocardial infarction with SI of 2.05 (95% CI 1.07 to 3.92) for male shift workers. For female shift workers, interaction effects were found with high waist-hip ratio (SI 4.0, 95% CI 1.12 to 14.28) and elevated triglycerides (SI 5.69, 95% CI 1.67 to 19.38). CONCLUSION: Shift work and some established coronary risk factors have significant interactions.

Cancer incidence in female laboratory employees: extended follow-up of a Swedish cohort study.

OBJECTIVES: Work in chemical laboratories is associated with exposure to chemicals, of which some are known or suspected carcinogens. A cohort study of laboratory workers in Stockholm followed until 1992 showed an excess of hematolymphatic malignancies in chemical laboratories and an excess of breast cancer among women working for more than 10 years in such laboratories. The follow-up of this cohort has now been extended by 20 years. METHODS: The cohort comprised 2245 female laboratory workers who are employed for >1 year from 1950 to 1989. Information on employment periods and type of laboratory ('chemical' or 'non-chemical') was obtained from employee registers. Cancer diagnoses from 1958 to 2012 were obtained from the Swedish Cancer Registry. RESULTS: There were 383 cases of cancer (SIR=0.93 (95% CI 0.84 to 1.02)). The risk of breast cancer was elevated, of borderline statistical significance, among those who had worked for at least 10 years in chemical laboratories (SIR=1.41 (95% CI 0.99 to 1.95) 36 cases). The breast cancer risk was especially high in women who had worked for more than 10 years in chemical labs before 1970 (SIR=3.76 (95% CI 1.72 to 7.14), nine cases). There was no excess of breast cancer in non-chemical labs (SIR=0.77 (95% CI 0.54 to 1.07), 35 cases). The number of hematolymphatic cancer was no longer significantly elevated. CONCLUSIONS: The increased risk of breast cancer, as well as the earlier noted excess of hematolymphatic malignancies, may be related to exposure to carcinogenic chemicals/organic solvents (eg, benzene) used in chemical laboratories, especially during earlier periods.

Daily text messages used as a method for assessing low back pain among workers.

OBJECTIVES: To evaluate a method for collecting data concerning low back pain (LBP) using daily text messages and to characterize the reported LBP in terms of intensity, variability, and episodes. STUDY DESIGN AND SETTING: We conducted a cohort study of LBP among workers used by a mining company. The participants were asked to answer the question "How much pain have you had in your lower back in the last 24 hours on a scale from 0 to 10, where 0 = no pain and 10 = the worst pain imaginable" once a day for 5 weeks, with this process being repeated 6 months later. RESULTS: A total of 121 workers participated in the first period of data collection, and 108 participated in the second period. The daily response rate was 93% for both periods, and cluster analysis was shown to be a feasible statistical method for clustering LBP into subgroups of low, medium, and high pain. The daily text messages method also worked well for assessing the episodic nature of LBP. CONCLUSION: We have demonstrated a method for repeatedly measuring of LBP using daily text messages. The data permitted clustering into subgroups and could be used to define episodes of LBP.

Work situation and self-perceived economic situation as predictors of change in burnout--a prospective general population-based cohort study.

BACKGROUND: Sick leave rates due to mental and behavioural disorders have increased in Sweden during the last decades. The aim of this prospective study was to investigate changes in the level of burnout in a working subset of the general population and to identify how such changes relate to changes in work situation and self-perceived economic situation. METHODS: A cohort of 1000 persons from a subset of the 2004 northern Sweden MONICA (Multinational Monitoring of Trends and Determinants in Cardiovascular Disease) general population survey was followed over a five-year period (2004-2009). In total, 623 persons (323 women and 300 men) were included in the analysis. Burnout levels were measured at baseline and follow-up using the Shirom Melamed Burnout Questionnaire. Risk factors were assessed at both measuring points. RESULTS: In the whole study cohort, a small (-0.15) but statistically significant reduction in burnout level was found. No differences in change of burnout were found between men and women. Constant strain at work, an increased risk of unemployment, and a perceived worsening of economic situation during the study time period were related to an increased burnout level. An accumulation of these risk factors was associated with increased burnout level. CONCLUSIONS: Risk factors in work situation and self-perceived economy are related to changes in burnout level, and special attention should be directed towards persons exposed to multiple risk factors.

[Exercise reduced the need for operation in lumbar spinal stenosis. Circulatory load in the form of cycling gave good effect]. / Träning minskade behovet av operation vid lumbal spinal stenos--Belastning av cirkulationsapparaten i form av cykling gav bra effekt.

Conservative treatment is being reported to relieve walk related leg pain or improve life quality in patients with lumbar spinal stenosis. Such treatment often combines various interventions, making it difficult to identify single effective measures. At our clinic, specialized in spine surgery, the care of the patients with lumbar spinal stenosis starts with a 4 months training program when the patient typically uses a stationary bike at a circulatory load of about 70% of maximal capacity. Need of surgery is evaluated after the training period. The present study compares oxygen uptake capacity and walking capacity before and after the training period. The main findings are: no clear correlation between change of oxygen uptake capacity and change of walking distance; no correlation between individual cauda equina cross-sectional area and improvement of walking distance during the training program; almost half of the patients who completed the training program felt their lumbar spinal stenosis symptoms improved to such an extent that surgery was not required (26/54).

Case fatality of myocardial infarction among shift workers.

PURPOSE: Shift work has been associated with an excess risk of cardiovascular disease (CVD) and more specifically myocardial infarction (MI). The majority of the studies that found a positive association between shift work and CVD have been based on incidence data. The results from studies on cardiovascular-related mortality among shift workers have shown little or no elevated mortality associated with shift work. None of the previous studies have analysed short-term mortality (case fatality) after MI. Therefore, we investigated whether shift work is associated with increased case fatality after MI compared with day workers. METHODS: Data on incident cases with first MI were obtained from case-control study conducted in two geographical sites in Sweden (Stockholm Heart Epidemiology Program and Västernorrland Heart Epidemiology Program), including 1,542 cases (1,147 men and 395 women) of MI with complete working time information and 65 years or younger. Case fatality was defined as death within 28 days of onset of MI. Risk estimates were calculated using logistic regression. RESULTS: The crude odds ratios for case fatality among male shift workers were 1.63 [95 % confidence interval (CI) 1.12, 2.38] and 0.56 (95 % CI 0.26, 1.18) for female shift workers compared with day workers. Adjustments for established cardiovascular risk factors such as diabetes type II and socio-economic status did not alter the results. CONCLUSION: Shift work was associated with increased risk of case fatality among male shift workers after the first MI.

Large outbreak of Cryptosporidium hominis infection transmitted through the public water supply, Sweden.

In November 2010, ≈27,000 (≈45%) inhabitants of Östersund, Sweden, were affected by a waterborne outbreak of cryptosporidiosis. The outbreak was characterized by a rapid onset and high attack rate, especially among young and middle-aged persons. Young age, number of infected family members, amount of water consumed daily, and gluten intolerance were identified as risk factors for acquiring cryptosporidiosis. Also, chronic intestinal disease and young age were significantly associated with prolonged diarrhea. Identification of Cryptosporidium hominis subtype IbA10G2 in human and environmental samples and consistently low numbers of oocysts in drinking water confirmed insufficient reduction of parasites by the municipal water treatment plant. The current outbreak shows that use of inadequate microbial barriers at water treatment plants can have serious consequences for public health. This risk can be minimized by optimizing control of raw water quality and employing multiple barriers that remove or inactivate all groups of pathogens.

Mortality attributable to occupational exposure in Sweden.

OBJECTIVES: The objective of this study was to estimate the mortality from cancer, cardiovascular, and respiratory diseases attributable to occupational exposure in Sweden. METHODS: Estimates were calculated for men and women separately, and we considered only deaths between 25-74 years of age. We considered cancer exposures/sites classified as I or 2a according to the International Agency for Research on Cancer (IARC). Acute myocardial infarction was the only included cardiovascular disease. Respiratory diseases comprised chronic obstructive pulmonary disease (COPD) asthma, pneumoconiosis and alveolitis. All deaths of pneumoconiosis and alveolitis were considered work-related. Estimates were based on the Swedish mortality in 2007. RESULTS: In total, we estimate that there are about 800 work-related deaths per year in the studied causes. The majority are due to acute myocardial infarction, with 126 deaths among women and 337 deaths among men attributable to job strain, shift work, exhaust gases, combustion products, or environmental tobacco smoke (ETS). There are 99 respiratory disease-related deaths, the vast majority from COPD (N=92). In total, 270 cancer deaths are estimated to be work-related. For men, half of the cases are attributed to asbestos exposure. CONCLUSIONS: Our results indicate that preventive measures to decrease occupational mortality should consider factors associated with myocardial infarction such as job strain, shift work and exhaust gases from vehicles and combustion products. Exposures to factors associated with COPD, such as dust, also seem important to prevent.

External review and validation of the Swedish national inpatient register.

BACKGROUND: The Swedish National Inpatient Register (IPR), also called the Hospital Discharge Register, is a principal source of data for numerous research projects. The IPR is part of the National Patient Register. The Swedish IPR was launched in 1964 (psychiatric diagnoses from 1973) but complete coverage did not begin until 1987. Currently, more than 99% of all somatic (including surgery) and psychiatric hospital discharges are registered in the IPR. A previous validation of the IPR by the National Board of Health and Welfare showed that 85-95% of all diagnoses in the IPR are valid. The current paper describes the history, structure, coverage and quality of the Swedish IPR. METHODS AND RESULTS: In January 2010, we searched the medical databases, Medline and HighWire, using the search algorithm "validat* (inpatient or hospital discharge) Sweden". We also contacted 218 members of the Swedish Society of Epidemiology and an additional 201 medical researchers to identify papers that had validated the IPR. In total, 132 papers were reviewed. The positive predictive value (PPV) was found to differ between diagnoses in the IPR, but is generally 85-95%. CONCLUSIONS: In conclusion, the validity of the Swedish IPR is high for many but not all diagnoses. The long follow-up makes the register particularly suitable for large-scale population-based research, but for certain research areas the use of other health registers, such as the Swedish Cancer Register, may be more suitable.

Work related factors and sick leave after rehabilitation in burnout patients: experiences from the REST-project.

INTRODUCTION: The aim of this study was to investigate the impact of psychosocial working conditions and coping strategies at work on change in sick leave level for patients on long-term sick leave due to burnout. METHODS: A cohort sample of patients (n = 117) on long-term sick leave due to burnout was analyzed. The patients answered a questionnaire at baseline and sick leave information was collected from the Swedish Social Insurance Agency at baseline and at follow-up 2 years later. Two groups were formed depending on whether the patients had "improved" and reduced their sick leave level (56%) or if the sick leave level was "unchanged" (44%) at follow-up. The association between change in sick leave and predictors measuring psychosocial working conditions and coping strategies at work were analyzed using logistic regression. RESULTS: The predictor, low control at work, was associated with unchanged sick leave at follow-up. When background characteristics were taken into account, usage of covert coping towards supervisors and covert coping towards workmates, respectively, also predicted unchanged sick leave level. High overcommitment was of borderline significance and associated with a reduced sick leave level at follow-up. CONCLUSIONS: Patients with burnout who have experienced low control at work and used covert coping towards supervisors and/or workmates have a higher risk of not reducing their sick leave after rehabilitation. The workplace may contribute to a reduction of sick leave lengths with a more flexible work environment and improvement in communication strategies for employees and supervisors.

Burnout, working conditions and gender--results from the northern Sweden MONICA Study.

BACKGROUND: Sick-leave because of mental and behavioural disorders has increased considerably in Sweden since the late nineties, and especially in women. The aim of this study was to assess the level of burnout in the general working population in northern Sweden and analyse it's relation to working conditions and gender. METHODS: In this cross-sectional study the survey from the MONICA-study (Monitoring of Trends and Determinants in Cardiovascular Disease) in northern Sweden 2004 was used. A burnout instrument, the Shirom Melamed Burnout Questionnaire (SMBQ), was incorporated in the original survey which was sent to a random sample of 2500 individuals with a response rate of 76%. After including only actively working people, aged 25-64 years, our study population consisted of 1000 participants (497 women and 503 men). ANOVA and multiple linear regression models were used. RESULTS: The prevalence of a high level of burnout (SMBQ >4.0) was 13%. Women had a higher level of burnout than men with the most pronounced difference in the age group 35-44 years. In both sexes the level of burnout decreased with age. Demand and control at work, and job insecurity were related to burnout. In women the level of education, socioeconomic position, work object, and working varying hours were of importance. Interaction effects were found between sex and work object, and sex and working hours. In a multiple regression analysis almost half of the gender difference could be explained by work related and life situational factors. CONCLUSIONS: Working life conditions contributed to the level of burnout in this actively working sample from the general population in northern Sweden. Especially in women, socioeconomic position was associated with burnout. The high level of burnout in women compared to men was partly explained by more unfavourable working conditions and life situational factors. Efforts to level out gender differences in burnout should probably focus on improving both working and socioeconomic conditions for women.

The effect of leisure-time physical activity on the risk of acute myocardial infarction depending on body mass index: a population-based case-control study.

BACKGROUND: High body mass index (BMI) and lack of physical activity have been recognized as important risk factors for coronary heart disease. The aim of the present study was to evaluate whether leisure-time physical activity compensates for the increased risk of acute myocardial infarction associated with overweight and obesity. METHODS: Data from the SHEEP (Stockholm Heart Epidemiology Program) study were used. The SHEEP study is a large Swedish population-based case-control study, comprising 1204 male and 550 female cases, and 1538 male and 777 female controls, conducted in Stockholm County, Sweden, during the period 1992-1994. Odds ratios (OR), together with 95 % confidence intervals (95% CI), were calculated using unconditional logistic regression, as estimates of the relative risks. RESULTS: Regular leisure-time physical activity was associated with a decreased risk of myocardial infarction among lean, normal-weight and overweight subjects, but not among obese subjects. Obese (BMI > or = 30) and physically active persons had an almost twofold risk of myocardial infarction, compared with normal-weight and sedentary persons (OR 1.85, 95% CI 1.07-3.18). The results were similar for men and women. CONCLUSION: While regular leisure-time physical activity seems to provide protection against myocardial infarction among lean, normal-weight and overweight subjects, this does not appear to be the case in obese subjects.

Vibration exposure and myocardial infarction incidence: the VHEEP case-control study.

OBJECTIVES: The main objectives of this study were to assess the risk of contracting first episode of myocardial infarction (MI) subsequent to vibration exposure and to assess a possible exposure-response relationship. METHODS: The Västernorrland heart epidemiology programme (VHEEP, a part of the Stockholm heart epidemiology programme study) was the source of the data. VHEEP is a population-based case-control study of risk factors for acute MI. Exposure information was collected by questionnaire and vibration exposure was assessed in 218 cases and 257 controls. Relative risks were estimated using odds ratios (ORs) from binary logistic regression. RESULTS: The results show that the OR of acute MI when exposed to vibration was 1.6 (95% CI: 1.1-2.4). It was not possible, however, to determine whether an exposure-response relationship was present. CONCLUSIONS: Working entailing vibrating machines is associated with an increased risk for acute MI.

The risk of acute myocardial infarction: interactions of types of physical activity.

BACKGROUND: Leisure time physical activity has previously been shown to be protective against cardiovascular disease. We estimated the influence of exercise, occupational physical activity, and household work with regard to risk of acute myocardial infarction (MI). Special interest was focused on potential interaction among these aspects of physical activity. METHOD: We analyzed data from a large population-based case-control study conducted in Stockholm, Sweden, 1992-1994. Cases comprised 1204 men and 550 women, age 45-70 years, who experienced their first MI during the study period. The controls, 1538 men and 777 women, were randomly selected from the study base, matched on sex, age, and hospital catchment area. The results were adjusted for several potential confounding factors. RESULTS: Exercise, walking or standing at work, and doing demanding household work were all associated with decreased risk of acute MI; the estimated relative risks (RRs) ranged from 0.31 to 0.90 when all cases (fatal and nonfatal) were considered. In contrast, lifting or carrying at work, and an occupational workload perceived to be strenuous, were related to an increased risk of MI (RRs ranging from 1.10-1.57). We observed a synergistic benefit from exercise and walking or standing at work, and from household work and walking or standing at work. CONCLUSION: Aerobic physical activities such as exercise or walking at work seemed to reduce the risk of MI, whereas anaerobic activities such as heavy lifting at work were related to increased risk of MI.

Myocardial infarction among professional drivers.

BACKGROUND: Professional drivers are at an increased risk of myocardial infarction but the underlying causes for this increased risk are uncertain. METHODS: We identified all first events of myocardial infarction among men age 45-70 years in Stockholm County for 1992 and 1993. We selected controls randomly from the population. Response rates of 72% and 71% resulted in 1067 cases and 1482 controls, respectively. We obtained exposure information from questionnaires. We calculated odds ratios (ORs), with and without adjustment for socioeconomic status, tobacco smoking, alcohol drinking, physical inactivity at leisure time, overweight status, diabetes and hypertension. RESULTS: The crude OR among bus drivers was 2.14 (95% confidence interval = 1.34-3.41), among taxi drivers 1.88 (1.19-2.98) and among truck drivers 1.66 (1.22-2.26). Adjustment for potential confounders gave lower ORs: 1.49 (0.90-2.45), 1.34 (0.82-2.19) and 1.10 (0.79-1.53), respectively. Additional adjustment for job strain lowered the ORs only slightly. An exposure-response pattern (by duration of work) was found for bus and taxi drivers. CONCLUSIONS: The high risk among bus and taxi drivers was partly explained by unfavorable life-style factors and social factors. The work environment may contribute to their increased risk. Among truck drivers, individual risk factors seemed to explain most of the elevated risk.

The risk of myocardial infarction is enhanced by a synergistic interaction between serum insulin and smoking.

OBJECTIVES: To evaluate the relationship between levels of serum insulin, the homeostasis model assessment (HOMA) and IGF-binding protein-1 (IGFBP-1) as factors related to myocardial infarction (MI) risk, and their interaction with lifestyle-related risk factors. DESIGN: The Stockholm epidemiology programme (SHEEP), a case-control study, consisting of 749 first-time MI cases (510 men, 239 women) and 1101 healthy controls (705 men, 396 women) was used. METHODS: The risk of developing MI was assessed by calculating odds ratios (OR) and synergistic interactions (SI) between serum insulin, IGFBP-1, HOMA and other variables related to MI risk (including smoking) in men and women. RESULTS: Subjects with elevated levels of insulin and HOMA (>75th percentile) had increased MI risks when compared with individuals with low levels. ORs for elevated insulin and HOMA (adjusted for age and residential area) for men: insulin 1.6 (95% confidence interval (CI) 1.3-2.1) and HOMA 1.5 (95% CI 1.1-1.9) and for women: insulin 2.1 (95% CI 1.5-2.9) and HOMA 1.9 (95% CI 1.3-2.8). Women with low levels of IGFBP-1 (<10th percentile) showed a tendency towards elevated MI risk even if this was not statistically significant (OR 1.5 (95% CI 0.9-2.6)). Smokers with high levels of serum insulin had greatly increased MI risk (OR for men: 4.7 (95% CI 3.0-7.2) and OR for women: 8.1 (95% CI 4.5-14.8)). SI scores based upon these interactions were statistically significant. CONCLUSIONS: These results might have preventive cardiovascular implications as they clearly suggest that subjects with insulin resistance are particularly susceptible to the hazards of smoking.