STUDY OBJECTIVE: To explore the association between job characteristics and plasma fibrinogen concentrations. DESIGN: Cross sectional design. SETTING: The Greater Stockholm area. SUBJECTS: A total of 1018 men and 490 women aged 45-70 who were randomly selected from the general population during 1992-1994. They were all employed and had no history of myocardial infarction. MAIN RESULTS: 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 (job control and psychological demands) were assigned by linking each subject's occupational history with a work organisation exposure matrix. Job strain was defined as the ratio between demands and control. In univariate analyses, expected linear trends were found in three of four tests of association between high plasma fibrinogen and low control (the self reported score for women and the inferred score for both sexes), in one of four tests of association between high plasma fibrinogen and high demands (the inferred score for women) and in two of four tests of association between high plasma fibrinogen and job strain (the inferred score for both sexes). Multiple logistic regression analyses showed that men in the inferred job strain group have an increased risk of falling into the increased plasma fibrinogen concentration group (above median level of the distribution) (odds ratio (OR) 1.2; 95% CI 1.0, 1.5) after adjustment for the variables that were associated with plasma fibrinogen in the univariate analyses. In women, low self reported control, high inferred demand, and inferred job strain were significantly associated with increased plasma fibrinogen concentration (OR 1.3; 95% CI 1.0, 1.8, OR 1.5; 95% CI 1.0, 2.2, OR 1.5; 95% CI 1.1, 2.2, respectively). CONCLUSIONS: These results indicate that adverse job characteristics may be related to plasma fibrinogen concentrations and this relation is more relevant in female workers. The clearest evidence for psychosocial effects on plasma fibrinogen seems to be with job control and the associations are clearer for the objective than for the self report variables.
OBJECTIVES: To evaluate the influence of consumption of filtered and boiled coffee, on the incidence of first nonfatal myocardial infarction. DESIGN: Population-based case-control study. SETTING AND SUBJECTS: The study base consisted of the population 45-65/70 years-old in two Swedish counties, Stockholm and Västernorrland, 1992/93-94. In all, 1943 cases of first nonfatal myocardial infarction were identified. For each case one control was selected from the study base concurrently with disease incidence by matching the sex, age and place of residence of the case. Information about coffee consumption and other factors was obtained by mailed questionnaire and a medical examination. The participation rate was 85% amongst cases and 74% amongst controls. RESULTS: Men with a reported consumption of 7-9 dL filtered coffee per day showed an increased incidence of first myocardial infarction compared with consumers of 3 dL day-1 or less (RR: 1.32; 95% CI: 1.03-1.70). A consumption of at least 10 dL day-1 was associated with an RR of 1.93 (95% CI: 1.42-2.63) for filtered and 2.20 (95% CI: 1.17-4.15) for boiled coffee. Amongst women, no clear association was seen between consumption of filtered coffee and myocardial infarction but consumption of boiled coffee tended to be related to an increased incidence. Comparing subjects drinking boiled coffee with those drinking filtered coffee and adjusting for the amount consumed gave an increased incidence for boiled coffee amongst both men (RR: 1.41; 95% CI: 1.07-1.80) and women (RR: 1.63; 95% CI: 1.04-2.56). CONCLUSIONS: Consumption of boiled coffee appears to increase the incidence of first nonfatal myocardial infarction. This increased incidence is consistent with randomized trials showing an adverse impact of boiled coffee on blood lipids.
OBJECTIVE: Our objectives were to study anger as a trigger of acute myocardial infarction (MI) and to explore potential effect modification by usual behavioral patterns related to hostility. METHODS: This study was a case-crossover study within the Stockholm Heart Epidemiology Program. Exposure in the period immediately preceding MI was compared with exposure during a control period for each case. From April 1993 to December 1994, 699 patients admitted to coronary care units in Stockholm County were interviewed. RESULTS: During a period of 1 hour after an episode of anger, with an intensity of at least "very angry," the relative risk of MI was 9.0 (95% CI, 4.4-18.2). In patients with premonitory symptoms, the time of disease initiation may be misclassified. When restricting the analyses to those without such symptoms, the trigger risk was 15.7 (95% CI, 7.6-32.4). The possibility of examining effect modification was limited by a lack of statistical power (eight exposed cases). Results of the analyses suggested, however, an increased trigger effect among subjects reporting nonhostile usual behavior patterns, nonovert strategies of coping with aggressive situations (not protesting when being treated unfairly), and nonuse of beta-blockers. CONCLUSIONS: The hypothesis that anger may trigger MI is further supported, with an increased risk lasting for approximately 1 hour after an outburst of anger. It is suggested that the trigger risk may be modified by personal behavior patterns.
To study possible triggering of first events of acute myocardial infarction by heavy physical exertion, the authors conducted a case-crossover analysis (1993-1994) within a population-based case-referent study in Stockholm County, Sweden (the Stockholm Heart Epidemiology Program). Interviews were carried out with 699 myocardial infarction patients after onset of the disease. These cases represented 47 percent of all cases in the study base, and 70 percent of all nonfatal cases. The relative risk from vigorous exertion was 6.1 (95% confidence interval: 4.2, 9.0). The rate difference was 1.5 per million person-hours, and the attributable proportion was 5.7 percent. The risk was modified by physical fitness, with an increased risk being seen among sedentary subjects as in earlier studies, but the data also suggested a U-shaped association. In addition, the trigger effect was modified by socioeconomic status. Premonitory symptoms were common, and this implies risks of reverse causation bias and misclassification of case exposure information that require methodological consideration. Different techniques (the use of the usual-frequency type of control information, a pair-matched analysis, and a standard case-referent analysis) were applied to overcome the threat of misclassification of control exposure information. A case-crossover analysis in a random sample of healthy subjects resulted in a relative risk close to unity, as expected.
An increased risk for myocardial infarction (MI) related to environmental tobacco smoke (ETS) exposure has previously been reported, but several aspects of the association are still uncertain. We studied the MI risk associated with ETS exposure among 334 nonfatal never-smoking MI cases and 677 population controls, 45-70 years of age, in Stockholm County. A postal questionnaire with a telephone follow-up provided information on ETS exposure and other potential risk factors for MI. After adjustment for age, gender, hospital catchment area, body mass index, socioeconomic status, job strain, hypertension, diet, and diabetes mellitus, the odds ratio for MI was 1.58 (95% confidence interval = 0.97-2.56) for an average daily exposure of 20 cigarettes or more from the spouse. Combined exposure from spouse and work showed an increasing odds ratio for MI, up to 1.55 (95% confidence interval = 1.02-2.34) in the highest category of weighted duration, that is, more than 90 "hour-years" of exposure (1 "hour-year" = 365 hours, or 1 hour per day for 1 year). In addition, more recent exposure appeared to convey a higher risk. Our data confirm an increased risk of MI from exposure to ETS and suggest that intensity of spousal exposure, combined exposure from spouse and work, and time since last exposure are important.
OBJECTIVES: To analyse differences in myocardial infarction incidence between two Swedish counties and to evaluate the importance of major risk factors for the observed differences. DESIGN: The incidence of first myocardial infarction was studied using information from registers. For a number of risk factors of myocardial infarction, the prevalence as well as the relative risk was estimated from population controls of case-control studies in the two areas. SUBJECTS: Men and women aged 45-64 years in Stockholm and Västernorrland County 1993-94. MAIN OUTCOME MEASURES: Relative risks (RRs) and impact fractions were used to evaluate the importance of differences in risk factor prevalence for differences in myocardial infarction incidence between the two areas. RESULTS: The incidence of first myocardial infarction was higher in Västernorrland than in Stockholm amongst both men (RR = 1.23; 95% CI = 1.08-1.40) and women (RR = 1.41; 95% CI = 1.11-1.79). Obesity and increased levels of blood serum lipids were more prevalent in Västernorrland than in Stockholm amongst men with impact fractions of 6 and 9-11%, respectively. Amongst women, corresponding differences were not seen, but job strain and shift work tended to be more common in the more northern area. Current smoking was more frequent in Stockholm, particularly for women. CONCLUSIONS: The incidence of first myocardial infarction was higher in Västernorrland than in Stockholm in both genders. A higher prevalence of obesity and elevated blood serum lipids may explain, in part, this excess incidence amongst men, but amongst women the causes of the higher incidence in the more northern area remain largely unclear.
OBJECTIVES: Middle-aged men have often been the subjects of multifactorial studies of myocardial infarction (MI) risk factors. One major objective of the SHEEP study was to compare the effects of different MI risk factors in women and men. DESIGN: SHEEP (Stockholm Heart Epidemiology Program) is a population-based case-referent study of causes of MI (first event) in Swedish women and men aged 45-70 years. During the period 1992-94, 2246 cases of MI were identified; 34% of the cases were women and 27% of the cases were fatal. One referent per case was chosen randomly from the Stockholm County population after stratification for the case's sex and age. Logistic regression was used to estimate the relative risks associated with risk factors of primary interest (diabetes, hypercholesterolaemia, hypertriglyceridaemia, hypertension, overweight, physical inactivity, smoking and job strain). RESULTS: The relative risk estimates ranged from 1.5 to 4.4 in women and from 1.3 to 2.9 in men (results for nonfatal cases and their referents). None of the 95% confidence intervals included 1.0. The relative risks were higher in the women than in the men (101-180%). The absolute risks, however, were all lower in the women than in the men. Estimates of Rothman's synergy index for gender ranged from 1.0 (hypertension) to 1.8 (current smoking). CONCLUSIONS: The indications of some effect modification due to sex (stronger risks in men for certain exposures) invoke the question of possible mechanisms.
The objectives are to examine if the excess risk of myocardial infarction from exposure to job strain is due to interaction between high demands and low control and to analyse what role such an interaction has regarding socioeconomic differences in risk of myocardial infarction. The material is a population-based case-referent study having incident first events of myocardial infarction as outcome (SHEEP: Stockholm Heart Epidemiology Program). The analysis is restricted to males 45-64 yr of age with a more detailed analysis confined to those still working at inclusion. In total, 1047 cases and 1450 referents were included in the analysis. Exposure categories of job strain were formed from self reported questionnaire information. The results show that high demands and low decision latitude interact with a synergy index of 7.5 (95% C.I.: 1.8-30.6) providing empirical support for the core mechanism of the job strain model. Manual workers are more susceptible when exposed to job strain and its components and this increased susceptibility explains about 25-50% of the relative excess risk among manual workers. Low decision latitude may also, as a causal link, explain about 30% of the socioeconomic difference in risk of myocardial infarction. The distinction between the interaction and the causal link mechanisms identifies new etiologic questions and intervention alternatives. The specific causes of the increased susceptibility among manual workers to job strain and its components seem to be an interesting and important research question.
OBJECTIVES: The aim of the present case-referent study was to investigate the incidence of myocardial infarction among male professional drivers, taking the type of vehicles and area of residence into account. METHODS: The study base comprised all men aged 30-74 in five counties in middle Sweden during 1976-81 or 1976-84. Incident cases of the first episode of myocardial infarction were identified from registers of hospital admissions and causes of deaths. Referents were selected randomly from the study base. Information about occupation was obtained from the national censuses in 1970 and 1975. The possible impact from tobacco smoking and overweight were evaluated by simulations in combination with indirect data on these factors. RESULTS: The incidence of myocardial infarction was increased among bus drivers in Stockholm (relative risk (RR) = 1.53, 95% confidence interval (95% CI) 1.15-2.05), and among taxi drivers both in Stockholm (RR 1.65, 95% CI 1.30-2.11) and in the surrounding rural counties (RR 1.82, 95% CI 1.17-2.82). A smaller increase was found among long distance lorry drivers, whereas the relative risk among short distance lorry drivers was close to unity. Indirect comparisons make it unlikely that the excess among bus drivers in Stockholm could be explained by uncontrolled confounding from tobacco smoking or overweight. A very high proportion (more than 80%) of urban bus drivers in Sweden report a combination of high psychological demands and low control at work. CONCLUSIONS: Different types of drivers are at different risk of myocardial infarction. Bus drivers in urban areas seem to be at an increased risk, which is unlikely to be explained by uncontrolled confounding from tobacco smoking or overweight. Psychosocial work conditions may play a part in the increased incidence of myocardial infarction among urban bus drivers and should be investigated further.
The aim of the study was to investigate whether workers in jobs dominated by the opposite sex have an increased risk of myocardial infarction (MI). A case-referent study was carried out to estimate the relative risk of first MI in different occupational groups. The study base comprised all men and women in five counties in the middle of Sweden during 1976-84. Cases of MI were identified from both hospital discharge records and death records. Information on occupation was obtained from two consecutive censuses. Primary health related selection was analysed for men with data from the physical examination of conscripts to compulsory military service in 1969-70 combined with data from the censuses of 1970-90 and data on early retirement in 1971-92. Increased risk of MI was found among both women (relative risk (RR) 1.41, 95% confidence interval (95% CI) 1.15 to 1.73) and men (1.21, 1.10 to 1.32) in blue collar jobs where men predominate, and among men with white collar jobs (1.26, 1.09 to 1.45) where women predominate. However, the increased risk among men in white collar jobs was probably due to negative health selection into these occupations. These results do not support the notion that being of the sexual minority in an occupation is in itself an important risk factor for MI.