Juhani Kirjonen

Work stress and risk of cardiovascular mortality: prospective cohort study of industrial employees

Abstract Objective: To examine the association between work stress, according to the job strain model and the effort-reward imbalance model, and the risk of death from cardiovascular disease. Design: Prospective cohort study. Baseline examination in 1973 determined cases of cardiovascular disease, behavioural and biological risks, and stressful characteristics of work. Biological risks were measured at 5 year and 10 year follow up. Setting: Staff of a company in the metal industry in Finland. Participants: 812 employees (545 men, 267 women) who were free from cardiovascular diseases at baseline. Main outcome measure: Cardiovascular mortality 1973-2001 from the national mortality register. Results: Mean length of follow up was 25.6 years. After adjustment for age and sex, employees with high job strain, a combination of high demands at work and low job control, had a 2.2-fold (95% confidence interval 1.2 to 4.2) cardiovascular mortality risk compared with their colleagues with low job strain. The corresponding risk ratio for employees with effort-reward imbalance (low salary, lack of social approval, and few career opportunities relative to efforts required at work) was 2.4 (1.3 to 4.4). These ratios remained significant after additional adjustment for occupational group and biological and behavioural risks at baseline. High job strain was associated with increased serum total cholesterol at the 5 year follow up. Effort-reward imbalance predicted increased body mass index at the 10 year follow up. Conclusions: High job strain and effort-reward imbalance seem to increase the risk of cardiovascular mortality. The evidence from industrial employees suggests that attention should be paid to the prevention of work stress.

Smoking and overweight as predictors of hospitalization for back disorders.

Study Design. A prospective cohort study. Objective. To study the relationship of smoking and overweight with severe back disorders leading to hospitalization. Summary of Background Data. Many epidemiological studies have shown an association between smoking or overweight and back pain, but the results are still equivocal. Longitudinal studies are few. Methods. A cohort of metal industry employees (n = 902) was studied for lifestyle, work history, and health in 1973 by questionnaire and interview. The weight of the subjects was measured and body mass index (kg/m2) was calculated. Based on intensity and duration, smoking was categorized as: never smoked (reference), stopped smoking, smoked ≤9 or >9 pack-years. Information on hospital admissions from 1973 to 2000 from the Finnish Hospital Discharge Register was linked to the data. Seventy-five individuals had been admitted to hospital because of back disorders. Intervertebral disc disorders and other common back disorders were analyzed separately. Cox proportional hazards regression was used to estimate the time between the assessment of potential risk factors and the first hospitalization for a back disorder. Results. The rate ratio of heavy smokers (>9 pack-years) for hospitalization because of intervertebral disc disorders was 3.4 (95% confidence interval 1.3–9.0) as compared with never-smokers, allowing for other risk factors. Accordingly, the rate ratio of body mass index >27.5 kg/m2 was 2.7 (1.1–6.45) as compared with people with normal weight. The results retained when patients with chronic back disease at baseline were excluded from the analyses. Other back-related diagnoses of hospitalization were not consistently associated with smoking or overweight. Conclusion. Heavy smoking and overweight predicted hospitalization for intervertebral disc disorders.

Is Incomplete Recovery From Work a Risk Marker of Cardiovascular Death? Prospective Evidence From Industrial Employees

Objective: A chronic lack of recovery from work during leisure time is hypothesized to indicate a health risk among employees. We examined whether incomplete recovery from work predicted cardiovascular mortality. Methods: This prospective cohort study involved 788 industrial employees (534 men, 254 women, mean age 37.3, SD = 12.0) who were initially free from cardiovascular diseases. The baseline examination in 1973 determined cases of cardiovascular disease, cardiovascular risk factors, and the extent of recovery from work. Data on mortality in 1973 to 2000 were derived from the national mortality register. Results: Sixty-seven cardiovascular deaths and 102 deaths from noncardiovascular causes occurred during the mean follow-up of 25.6 years. Employees who seldom recovered from work during free weekends had an elevated risk of cardiovascular death (p = .007) but not of other mortality (p = .82). The association between incomplete recovery and cardiovascular death remained after adjustment for age, sex, and 16 conventional risk factors, including occupational background, cholesterol, systolic pressure, body mass index, smoking, alcohol consumption, physical inactivity, depressive symptoms, fatigue, lack of energy, and job stress. The association was not explained by deaths that occurred close to the assessment of recovery from work. Conclusions: This study suggests that incomplete recovery from work is an aspect of the overall risk profile of cardiovascular disease mortality among employees. BMI = body mass index; CHD = coronary heart disease; CI = confidence interval; ICD = International Classification of Diseases.

The Acquisition of Professional Expertise—a challenge for educational research

This article examines the acquisition of professional expertise from the educational viewpoint and outlines emerging approaches to research on expertise. The starting points are the need to reflect the nature and content of expertise in the changing world and the aim to understand the preconditions for integrating the viewpoints of working life and education in developing prerequisities for expertise in educational contexts. The section after the Introduction briefly reviews how expertise has been conceptualized in recent research. The next section deals with the role of higher education in developing expertise from the viewpoint of constructivist approaches in research on learning. Then current challenges and alternatives for educational research on the acquisition of future expertise are outlined.

Sleep disturbances as predictors of hospitalization for back disorders : A 28-year follow-up of industrial employees

Study Design. A prospective cohort study. Objective. To study the relationship of sleep disturbances with severe back disorders leading to hospitalization. Summary of Background Data. Sleep disturbances are associated with persistent pain syndromes, but little is known about their relationship with back disorders. Methods. The first hospital admission for back disorders from 1973 to 2000 was studied in a cohort of metal industry workers (n = 902). The occurrence of sleep disturbances at baseline was categorized as: none; 1 type (either difficulties in falling asleep/waking up at night or nightmares); or both types. Cox proportional hazards regression was used to estimate the time between the assessment of risk factors and first hospital admission for back disorders. Results. Those individuals who had 1 type of sleep disturbance had a 2.1-fold (95% confidence interval 1.1−3.8) risk of back-related hospitalization, and those with both types of disturbance a 2.4-fold (1.2−4.6) risk, compared with those with no sleep disturbances. The hazard ratios were 2.1; 1.0−4.6 and 2.9; 1.2−7.1, respectively, when patients with chronic back disease or recurrent back symptoms at baseline were excluded from the analyses. Conclusion. These findings suggest that sleep disturbances are predictive of hospitalization for back disorders. The mechanism underlying this association warrants further study.

Serum Lipids and Low Back Pain : An Association? : A Follow-up Study of a Working Population Sample

Study Design. Cohort study with 5-, 10-, and 28-year follow-up. Objectives. To examine associations between baseline serum lipid concentrations and later low back pain (LBP). Summary of Background Data. Atherosclerosis of the lumbar vessels has been suggested as a mechanism leading to disc degeneration and LBP. Cholesterol is considered essential for atherosclerosis development. Methods. A sample (n = 902) of employees in an engineering company was examined for serum total cholesterol and triglycerides, body mass index (BMI), smoking, exercise, work history, and LBP in 1973. By November 2000, 232 subjects had died. In 1978, 748 (84% of the survivors), in 1983, 654 (76%), and in 2000, 546 (81%) responded to a follow-up questionnaire. Results. In men, baseline serum total cholesterol predicted new cases of radiating LBP in the 5-year follow-up (highest tertile vs. lowest: odds ratio [OR], 2.5; 95% confidence interval [CI], 1.1–5.9) and in the 10-year follow-up (OR, 2.8; 95% CI, 1.3–6.1), adjusted for age, occupational class, work history, BMI, smoking and exercise. Also, serum triglycerides predicted new cases in the latter examination (OR, 2.6; 95% CI, 1.2–5.8). In women, no associations were seen until the 10-year follow-up, when their results were similar to those in men. In the total material, serum total cholesterol predicted radiating LBP reported both at the 10- and the 28-year follow-up. Conclusions. High serum lipids predicted incident radiating LBP, consistent with the atherosclerosis-LBP hypothesis.

Persistence of low back pain reporting among a cohort of employees in a metal corporation : A study with 5-, 10-, and 28-year follow-ups

Abstract Low back pain (LBP) is a common symptom among adults but little is known about its persistence over time in defined populations. The aim of this study was to examine the persistence of LBP among a cohort of industrial employees studied in four successive surveys during a total of 28 years. Cross‐tabulations and logistic regression was used to estimate the interdependence of LBP occurrence at the surveys. At baseline, 54% of the subjects reported local LBP and 25% LBP radiating to the lower limb(s). Persistent or recurrent LBP was common. Of those with LBP at baseline, 75, 73, and 88% reported it also at the 5‐, 10‐ or 28‐year follow‐up, respectively. Of those with radiating pain, 66, 65, and 69% were symptomatic 5, 10, or 28 years later. The onset of reporting LBP increased during follow‐up. Of those without local LBP at baseline, 33, 37 and 64% had pain at the 5‐, 10‐, or 28‐year follow‐up, respectively. Of those without radiating LBP, 17, 22, and 46% had pain at the 5‐, 10‐, or 28‐year follow‐up. The odds ratio of local LBP at the 5‐, 10‐, or 28‐year follow‐up for those with such pain at baseline vs. not were 6.0 (95% CI 4.3–8.3), 4.7 (3.3–6.6) and 4.0 (2.6–6.3), adjusted for age, gender and occupational class. The respective figures for radiating LBP were 8.5 (5.7–12.5), 6.7 (4.4–10.1) and 2.3 (1.5–3.6). We conclude that LBP is commonly recurrent.

Stability and prediction of physical activity in 5-, 10-, and 28-year follow-up studies among industrial employees.

The aim of the study was to examine the stability of voluntary and household physical activity (PA) and to compare it with that of the use of the most common stimulants. The prospective cohort study comprised of follow‐ups at 5, 10, and 28 years at baseline in 1973 in four plants of an industrial corporation in Finland. A systematic, non‐proportional sample (n=902, age range 18–64 years) stratified for age, gender, and occupational status was drawn from the employees. Scores of PA were based on a questionnaire and interviews. Logistic regression models with proportional odds assumptions were counted. The 5‐year stability (Spearmans ρ) of PA time was 0.44 (PA intensity 0.44), the respective 10‐year coefficient was 0.26 (0.32), and that in the 28‐year follow‐up was 0.18 (0.20). The stability of PA decreased rapidly from 1973 to 1983 and more slowly thereafter. Changes along the follow‐up reflect a polarization of the distributions of PA within the sample. Age and an initially low level of activity were the strongest predictors of inactivity. The stability coefficient of smoking and alcohol consumption was twice as high as that of PA. Stimulant use was a greater factor in the individuals lifestyle than PA.

Low back pain, work absenteeism, chronic back disorders, and clinical findings in the low back as predictors of hospitalization due to low back disorders: a 28-year follow-up of industrial employees.

Study Design. Prospective cohort study. Objective. To study symptoms, chronic disorders, and clinical findings in the low back, and work absenteeism, as predictors of hospitalization. Summary of Background Data. Socioeconomic and lifestyle factors are associated with back-related hospitalization, but the significance in the working normal population of low back symptoms and clinical findings are not known. Methods. The cohort (n = 902) was drawn in 1973 from among employees in the metal industry (n = 2,653). The data were collected by questionnaire and a structured clinical assessment by a physiotherapist. Weight was measured. A sum score of local and radiating low back symptoms (frequency during the past year on a 4-point Likert scale) was categorized as no/yes and no/infrequent/frequent. Local and radiating symptoms were considered also separately. The data were linked with those from the Finnish Hospital Discharge Register during 1973 to 2000. Logistic regression and the Cox proportional hazard models were used. Results. As compared with persons without low back pain, those with frequent or radiating low back pain had an increased risk of hospitalization due to low back disorders (hazard rate ratio [HRR], 3.0; 95% confidence interval [CI], 1.4–6.5, and 3.7; 1.8–7.7, respectively) after adjustment for age, gender, and occupational class. Similarly, clinical findings (HRR, 2.4; 95% CI, 1.3–4.7), back-related absenteeism (HRR, 3.3; 95% CI, 1.6–6.7), and chronic low back disorders (HRR, 2.8; 95% CI, 1.5–5.4) predicted hospitalization. The associations persisted when further adjusted for smoking, body mass index, and distress symptoms at baseline. Conclusion. Frequent or radiating low back symptoms, chronic low back disorders, back-related work absenteeism, and having clinical findings in the low back predicted inpatient hospital care for low back disorders.

Psychosocial factors at work as predictors of hospitalization for back disorders: A 28-year follow-up of industrial employees

Study Design. A prospective cohort study. Objectives. To study the association of psychosocial factors at work with severe back disorders leading to hospitalization. Summary of Background Data. Some psychosocial factors at work have been related to back pain, but little is known about their predictive role in severe back disorders. Methods. Psychosocial factors at work were studied by questionnaire and interview in 1973 among a cohort of 902 metal industry employees. Information on hospital admissions for back disorders from the Finnish Hospital Discharge Register in 1973–2000 was linked to the data. Cox proportional hazards regression was used to estimate the time between the assessment of risk factors and the first hospital admission for intervertebral disc disorders (36 cases) and other back disorders (47 cases). Results. In a model including psychosocial factors and potential confounders, low job control versus high control was associated with a 3.2-fold risk (95% confidence interval, 1.3–7.8) of hospitalization for back disorders other than those of the intervertebral disc. The corresponding rate ratio for low versus high supervisor support was 2.9 (95% confidence interval, 1.3–6.3). Job demands, coworker support, and distress were not independently associated with these disorders. The result did not change when patients with chronic back disorder at baseline were excluded from the analysis. There was no association between psychosocial factors at work and hospitalizations for intervertebral disc disorders. Conclusion. Low job control and low supervisor support seem to increase the risk of hospitalization for back disorders other than intervertebral disc disorders.