The SHEEP (Stockholm HEart EPidemiology) Project

SHEEP is a major epidemiological study on cardiovascular disease and it’s biomedical risk factors. It is a case-referent study of the first myocardial infarction in men and women (1500 men and 700 women in the ages 45-70) and the same number of referents. It has been established, along with WOLF (WOrk, Lipids and Fibrinogen) as a collaborative effort with several various occupational health care teams, and regional research departments and institutes, hospital departments of medicine. Both projects are part of an EU collaboration including Tores Theorell, Michael Marmot, Johannes Siegrist, and others.

Anders Ahlbom, Johan Hallqvist, Christina Reuterwall, Ulf de Faire, Finn Diderichsen, Christer Hogstedt, Tores Theorell, Lars Alfredson, Per Gustavsson, Nils Plato, Eva Vingard, Piroska Ostlin et al.

The incidence of myocardial infarction (MI) has been shown to vary across different occupational, social, and ethnical groups, between geographic regions, and over time; those variations, however, can only partly be explained by between-group differences in the risk factors hypertension, hyperlipidimi, and smoking. A large number of other risk factors – some of them work related – have also been suggested. The present case-referent study will test several hypotheses concerning risk factors for MI, such as occupational exposure to chemical and/or psychosocial factors, social and environmental factors, dietary and smoking habits, and biological/medical factors. Special attention is paid to potential interaction between the various factors. The study will compromise approximately 2100 cases (1400 men and 700 women) of acute MI (first episode) in the Stockholm county area and the referents are chosen from the general population. Exposure information is collected through questionnaires and biomedical examination.

Several research and clinical units are cooperating in the project – Institute of Environmental Medicine and Department of Social Medicine at Karolinska Institute, the National Institute for Working Life and the National Institute of Psychosocial Factors and Health, Stockholm County units of Environmental Health, Social Medicine, and Occupational Health, Karolinska Hospital and the Departments of Medicine at each of the ten emergency hospitals in the Stockholm County area. Exposure information was collected 1992-1994 and the first results will be reported in 1996.

Financial support by Stockholm County Council, The Social Research Council, and The Medical Research Council.

Thanks to Yrkesmedicin for this information:
Department of Occupational Health, Karolinska Hospital
SE-171 76 Stockholm, Sweden
phone +46 8 517 730 56

The Relationship Between Job Strain and Fibrogen Levels

A Tsutsumi, Fukuoka, Japan, T Theorell, J Hallqvist, C Reuterwall, Stockholm, Sweden

In order to explore the relationship between plasma fibrinogen and job strain, referents of the SHEEP (a representative case-referent study of a first myocardial infarction in the Great Stockholm area during 1992-1994) were asked to respond to a questionnaire, and morning blood samples were collected. The self-reported job characteristics were measured by a Swedish version of the Karasek demand-control questionnaire. For inferred scoring of job characteristics, psychosocial exposure categories (decision latitude and psychological demands) were assigned by linking each subject’s occupational history with a work organization exposure matrix according to Johnson et al 1988. Job strain was defined as the ratio between demands and decision latitude.

In univariate analyses, age, BMI, smoking, hypertension, and history of cardiovascular disease were significantly associated with plasma fibrinogen in both genders. Marital status, the prevalence of angina pectoris and frequent night work were associated with plasma fibrinogen in men and the prevalence of diabetes, overwork (opposite direction), menopause, and hormone replacement therapy were associated with plasma fibrinogen in women. The relative risks of job characteristics for elevated fibrinogen levels (upper median levels) were calculated by a logistic regression model. The variables that were associated with plasma fibrinogen for each gender in the univariate analyses were chosen as covariates. When age adjusted, inferred strain was significantly associated with elevated fibrinogen level in men (Odds ratio (95%CI) = 1.4 (1.0–2.1)). This relation was borderline (1.4 (0.9–2.1)), however, when all the covariates had been adjusted for. In women, all three inferred job characteristics were associated with elevated fibrinogen level (2.0 (1.0–3.8) for decision latitude, 2.2 (1.1–4.5) for demands, and 2.1 (1.1–4.2) for strain) even when all the covariates had been adjusted for.

In conclusion, plasma fibrinogen was associated with inferred job characteristics in both genders. In men, a substantial part of the variance could be statistically explained by other risk factors.

Submitted by: Tores.Theorell@ipm.ki.se

Occupational chemical exposure and myocardial infarction. A study within Stockholm Heart Epidemiology Program (SHEEP)

Per Gustavsson, Nils Plato

A case-referent study of myocardial infarction is ongoing since the beginning of 1992. Data on chemical and psychosocial occupational factors are investigated, as well as social and individual risk factors. The purpose of the present study is to analyze the risk of myocardial infarction in relation to motor exhausts and other combustion products. The exposure to organic solvents, lead and dynamite will also be investigated. The occupational histories of 4600 cases and referents are evaluated and coded by an industrial hygienist. The study will be reported in 1997-1998.

Financial support: Swedish Council for Work Life Research.

Thanks to Yrkesmedicin for this information:
Department of Occupational Health, Karolinska Hospital
SE-171 76 Stockholm, Sweden
phone +46 8 517 730 56

Validation of vehicle-exhaust assessment in a cohort study of occupational related cardiovascular diseases (SHEEP)

Nils Plato, Marie Lewne, Per Gustavsson

The vehicle exhaust exposure has been assessed for 38 job categories in Stockholm county. The assessment is semiquantitatively done is seven exposure levels retrospectively since 1940 by five independent industrial hygienists. General exhausts as well as diesel exhausts were assessed. A consensus estimation was performed to compose the base for individual calculation of exhaust exposure for cases and controls in the SHEEP study. The aim of this study is to validate independent exhaust assessment. The study will be reported in 1997.

Psychosocial work environment and myocardial infarction among women in Stockholm – a SHEEP substudy Christina Reuterwall, Tores Theorell, Anders Ahlbom, Johan Hallqvist

Very few studies on work related risk factors for myocardial infarctions has comprised women, Nevertheless, indications of different reactions to occupational psychosocial conditions have been found. The SHEEP study will include almost 1500 women – of which 50% are cases and 50% referents. Exposure information is requested in psychological demands, level of control, and social support at work, together with a large number of different exposures/factors. Given the high prevalence of exposure to strenuous psychosocial work environment (about 20% in the study base) and the number of cases and referents in SHEEP, the study will be able to detect also modest increased risks of myocardial infarction in women, due to psychosocial work environment factors. Shall be reported 1998.

Financial support: Swedish Council for Work Life Research.

VIP (Vasternorrland’s Infarction Project) – jointly with SHEEP

Tohr Nilsson, Anders Knutsson, Per Gustavsson, Christina Reuterwall, Anders Ahlbom, Johan Hallqvist and others.

The SHEEP study is replicated in the county of Vasternorrland, using identical study design and exposure information retrieval techniques. Occupational exposures of particular interest in this area are combustion products, shift work, and vibrations. Cases will b e identified during 1993-1994, and the data collection will continue throughout 1995. Approximately 400 cases are expected to be included. To be reported in 1997.

Financial support: the Vasternorrland county council.

Risk factors for coronary heart disease in women: a joint analysis of data from three concurrent studies in the Stockholm area

Christina Reuterwall, Nina Rehnqvist, Karin Schenk-Gustafsson, Anders Ahlbom, Johan Hallqvist, Tores Theorell, Kristina Orth-Gomer

Coronary heart disease (CHD) is a major cause of death also among women (about 50% of all women die from CHD), yet very little is known about the causes of CHD in women. The “classical” risk factors – elevated serum lipid levels, hypertension, smoking, diabetes, and abdominal adipose tissue – increase the risk of CHD also in women. Different factors seem to have somewhat different impact on the risk of disease in men and women, however, and today’s knowledge of risk factors for CHD is based mainly on data on middle-aged men. The present study will use data collected in three concurrent CHD studies in the Stockholm area viz., SHEEP, KOK, and APSIS. Different hypotheses on CHD risk factors are tested in the different studies and all studies comprise female subjects. The outcomes under study are myocardial infarction (in SHEEP and KOK) and angina pectoris (in APSIS and KOK) and exposure information is collected in interviews or questionnaires. All three studies use similar questions on e.g. social factors, on psychosocial work environment, on physical activity, and – for the women – on reproductive factors. We will combine the common information from the three studies and analyze it jointly. We estimate that such an analysis will comprise exposure information on certain risk factors for altogether approximately 1500 women and 2400 men, which should contribute substantially tot he understanding of these risk factors, especially in women.

The analyses is performed in collaboration with the National Institute for Working Life, the Institute of Environmental Medicine at the Karolinska Institute, the Department of Social Medicine at Kronan, Sundbyberg, the national Institute of Psychosocial Factors and Health, the Department of Medicine at the Karolinska Hospital, To be reported 1997.

Financial support: FRN.

Thanks to Yrkesmedicin for this information:

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