Somatic risk factors for myocardial infarction among Swedish railway engine drivers.

BACKGROUND: Previous studies have indicated an increased incidence of myocardial infarction among railway engine drivers. OBJECTIVE: To analyse whether somatic risk factors for myocardial infarction among male drivers in different geographical areas in Sweden differed from that in general population samples drawn from the same geographical areas. DESIGN: A cross-sectional study comparing drivers and men from the general population. METHODS: Engine railway drivers aged 25-59 years (n = 2318) were compared with randomly selected men (n = 3016) with respect to their serum cholesterol, systolic and diastolic blood pressures and smoking habits. RESULTS: The levels of the risk factors did not differ between engine drivers and the reference groups except for the Stockholm area which showed a higher percentage of tobacco smokers as well as higher means for systolic and diastolic blood pressures. The risk ratio compared with the reference samples was significantly elevated in Stockholm but not in any of the other areas. CONCLUSIONS: These somatic risk factors for myocardial infarction do not explain the approximately 40% reported increase in myocardial infarction incidence among railway engine drivers. In the following study, psychosocial factors will also be examined.

Psychosocial risk factors for myocardial infarction among Swedish railway engine drivers [corrected].

BACKGROUND: Several earlier investigations have found an increased incidence of myocardial infarction among male drivers and, not least, among railway engine drivers. In a previous study we found that increased serum cholesterol, blood pressure or tobacco smoking did not explain this increased risk. OBJECTIVE: To investigate psychosocial factors and primarily work-related factors among male engine drivers. DESIGN: Engine drivers were compared with random population samples in a cross-sectional study. METHOD: Two thousand three hundred and eighteen engine drivers aged 25-59 years were compared with 331 randomly selected men who were mainly from the Göteborg MONICA population study. Job demands and job decision latitude as well as social support were the main factors compared. RESULTS: Job demands were reported as being significantly lower by both younger and older engine drivers compared to their referents (P = 0.002 and P = 0.0001, respectively). Decision latitude was reported as being lower by both younger and older engine drivers than among controls (P = 0.0001 for both groups). Engine drivers experienced deficient support from their superiors compared to the referents (P = 0.0001 for younger as well as older engine drivers). Low decision latitude was associated with significantly higher diastolic blood pressure (r = -0.11 and P = 0.0001), but otherwise there were no significant relationships between psychosocial work characteristics and somatic risk factors. CONCLUSIONS: The combination of low decision latitude and low social support seems to be a key factor in the increased risk of myocardial infarction among railway engine drivers. They generally undertake shift work which may be an additional risk factor for myocardial infarction.

Risk factors for myocardial infarction among Swedish railway engine drivers during 10 years follow-up.

BACKGROUND: Railway engine drivers have had an increased risk of myocardial infarction which could be due to reported low decision latitude and low social support but not to elevated somatic risk factors. OBJECTIVE: To study somatic and psychosocial risk factors for myocardial infarction among railway engine drivers prospectively. DESIGN: A prospective study of 2318 drivers followed for 10 years. METHODS: Risk factors were surveyed in conjunction with periodic health checks at 15 different centres but with common methodology and commonly used questionnaires. Questionnaire and register information on myocardial infarction during follow-up was recorded. RESULTS: Within this group of engine drivers, age, family history of myocardial infarction, systolic blood pressure and low body height were independent predictors of myocardial infarction, but diabetes, elevated serum cholesterol and smoking were not. Neither were a longer time in the occupation or work-related psychosocial factors. The drivers were all at the lower end of the decision authority and latitude scale and had low social support. With this limited span, it may be difficult to detect these variables as risk factors within this group. CONCLUSIONS: Several well-known, somatic risk factors for myocardial infarction were documented in this study, whereas psychosocial working conditions, which were common to all the drivers, were not significantly related to outcome.

Cancer incidence among male railway engine-drivers and conductors in Sweden, 1976-90.

During recent years, the relationship between exposure to magnetic fields and cancer has attracted increasing interest. In Sweden, train personnel are exposed to comparatively strong magnetic fields in their work. The aim of the present study was to investigate cancer incidence, particularly leukemia and brain tumors, among male railway engine drivers and conductors, respectively, and to compare their cancer incidence with that of the general male population. The study population comprised all male railway engine drivers (n = 7,466) and conductors (n = 2,272) who were ever employed at the Swedish State Railways during the period 1976-90. The study population was observed with regard to cancer incidence by means of the National Cancer Register for the period 1976-90. The total cancer incidence (all tumors included) among railway engine drivers was lower than in the general Swedish population. An increased incidence of lymphocytic leukemia was observed among railway engine drivers and conductors combined (relative risk = 2.3; 95 percent confidence interval = 1.3-3.2), with the same point estimate for both occupational groups. For brain tumor (astrocytoma), the observed relative risk was close to one. The study provides evidence of an excess risk of lymphocytic leukemia in railway engine drivers and conductors, workers with known occupational exposure to magnetic fields.

The effect of major railway accidents on the psychological health of train drivers--I. Acute psychological responses to accident.

The acute psychological reactions of 101 train drivers to on-the-track accidents were studied by means of clinical interviews and questionnaires (Impact of Event Scale, GHQ-20 and a questionnaire addressing stress symptoms, pre-accident expectancies and worries). More than half of the train drivers reported moderate to high intrusive distress (mean 11.3) within hours to days after the accident but only 1/3 reported symptoms of acute psychophysiological arousal. Intrusive symptoms related to visual impressions were most frequently reported. Avoidance was less prevalent (mean 8.8). Clinical interviews, relationship between pre-accident worries and severity of the acute responses and positive correlation between GHQ-scores relating to the fortnight preceding the accident and IES-intrusion scores, suggest that premorbid variables may influence the stress response. Involvement in more than two previous accidents invoked a feeling of vulnerability and produced stronger acute responses. Post-accident experiences involving various personal contacts did not correlate with the stress responses in this study and only a few drivers experienced such events in a negative way. Denial of the possibility of being involved in accidents was not associated with increased risk of strong acute responses, indicating that denial does not predict poor outcome in healthy persons exposed to situations where possibility of avoiding the event is outside the control of the person.

The effect of major railway accidents on the psychological health of train drivers--II. A longitudinal study of the one-year outcome after the accident.

The psychological impact on 101 train drivers of accidents causing major injuries or death to persons was studied by means of clinical interviews and questionnaires (Impact of Event Scale, General Health Questionnaire and a questionnaire addressing stress symptoms plus past and pre accident expectancies of being involved in accidents). The drivers were examined within hours to a few days after the accident and later at 1 month and 1 year. One month after the accident the symptoms of distress were significantly reduced and most so among the drivers with no preaccident risk experience according to self reports during the acute phase. A minor further reduction of distress was found at 1 year. Drivers with two or more previous accident experiences and those who had worried about being involved in accidents showed highest symptoms of distress at follow-up. Eleven out of 101 drivers reported sick leave more of than 1 week after the accident and this was related to higher intrusion scores. The few drivers who report longterm psychological distress are best predicted by a combination of acute high IES scores, experience of previous accidents and risk expectancy prior to the current accident. The study suggests that premorbid and non-accident related variables are more important for the 1 year psychological outcome of healthy drivers after on-the-track accidents than the stress event itself.

Cancer incidence among creosote-exposed workers.

Cancer incidence was studied among 922 creosote-exposed impregnators at 13 plants in Sweden and Norway. The subjects had been impregnating wood (eg, railroad cross-ties and telegraph poles), but no data on individual exposures were available. The study population was restricted to men employed during the period 1950-1975, and their cancer morbidity was checked through the cancer registries. The total cancer incidence was somewhat lower than expected, 129 cases versus 137 expected [standardized incidence ratio (SIR) 0.94]. Increased risks in both countries combined were observed for lip cancer (SIR 2.50, 95% confidence interval (95% CI) 0.81-5.83), skin cancer (SIR 2.37, 95% CI 1.08-4.50), and malignant lymphoma (SIR 1.9, 95% CI 0.83-3.78). Exposure to sunlight may have contributed to the risk of lip and skin cancer. The small number of cancer cases does not permit valid conclusions. The findings indicate that impregnating wood with creosote in earlier decades increased the risk of skin cancer.

The importance of variations in questionnaire administration.

A standardised Nordic questionnaire for the analysis of musculoskeletal symptoms was administered to Swedish bus drivers and shunters in two different ways. The first was a cohort study in which all questions were focused on musculoskeletal troubles, whilst the other was the administration of the standardised questionnaire during a general health examination. Higher frequencies of musculoskeletal troubles were reported in the cohort study. When this type of questionnaire was administered prior to the general health examination, no differences were seen, which may be an effect of focusing first on the musculoskeletal symptoms. It can thus be concluded that it is important, not only to use standardised questionnaires, but also to consider the way the questionnaire is administered when comparing the results from different studies.