Psychosocial work conditions associated with sickness absence among hospital employees.

BACKGROUND: Meaningfulness of the job, collaboration among colleagues, trustworthiness of the closest superior and bullying have previously been shown to be major covariates of intention to quit the job. AIMS: To test if these elements of the psychosocial work environment are also the most essential covariates of sickness absence. METHODS: A cross-sectional questionnaire study of hospital employees which sought information on elements of the psychosocial work environment, general health status, life style, age, gender and profession. Data on sickness absence were obtained from the employer's salary database. RESULTS: A total of 1809 hospital employees took part with a response rate of 65%. The mean age was 43 (range: 20-69) and 75% were female. Totally, 363 study participants (20%) had at least 14 days sickness absence (defined as high absence) during the preceding year. Associations between high sickness absence and 29 psychosocial work elements were analysed, adjusting for relevant confounders. Following multiple logistic regression analysis, three elements had an independent statistically significant association with high sickness absence: no exposure to bullying (odds ratio (95% confidence interval) 0.50 (0.33-0.77)), high meaningfulness of the job (0.71 (0.52-0.97)) and high trustworthiness of the closest superior (0.70 (0.54-0.92)). CONCLUSIONS: Elements of the psychosocial work environment which have previously been shown to have a significant independent association with intention to quit the job were also the most essential covariates of high sickness absence.

Job satisfaction and intention to quit the job.

BACKGROUND: Negative psychosocial work conditions may influence the motivation of employees to adhere to their job. AIMS: To elucidate the perception of psychosocial work conditions among Danish hospital employees who would quit their job if economically possible and those who would not. METHODS: A cross-sectional questionnaire study of hospital employees. The questionnaire gave information on elements of the psychosocial work environment (job demands, job influence, job support, management quality, exposure to bullying), general health status, sick-leave during the preceding year, life style (leisure time physical activity, alcohol intake and smoking habits), age, sex and profession. RESULTS: There were 1809 participants with a response rate of 65%. About a quarter (26%) reported that they would quit their job if economically possible; this rose to 40% among the 17% who considered their health mediocre or bad. In a final logistic regression model, six factors were identified as independently associated with the wish to quit or not: self-assessed health status, meaningfulness of the job, quality of collaboration among colleagues, age, trustworthiness of closest superior(s) and exposure to bullying. Based on these factors it was possible to identify groups with fewer than 15% wishing to quit, and similarly, groups where 50% or more would quit if this was economically possible. CONCLUSIONS: Psychosocial work conditions, in particular meaningfulness of the job, were independently associated with intention to quit the job if economically possible and relevant within different job categories.

Psychosocial stress among Danish vicars.

BACKGROUND: Burnout and depression are common among clergy members of several religions and denominations. Despite this, no studies have analysed whether differences in psychosocial workloads between vicars and others explain their higher prevalence of stress-related symptoms. AIMS: To test the hypothesis that elements of the job strain model (high work demands, low decision latitude and/or low job support) are mediators of the excess prevalence of stress-related health complaints among vicars compared with other employees in the Church of Denmark. METHODS: Data for this cross-sectional study were collected by means of a self-administered questionnaire sent to all employees in 500 Danish parishes (n = 2254). RESULTS: The study response rate was 73%, 35% of respondents were vicars and 43% were female. Compared with other employees, vicars felt quiet and relaxed less often (53 versus 67%), had less time for pleasure and relaxation (28 versus 11%) and felt happy and satisfied (53 versus 67%) less often. Vicars had significantly higher quantitative, cognitive and emotional work demands, lower work support, less influence on whom to collaborate with and less influence on their workload. Psychosocial workloads were more favourable for the vicars who had greater influence on job decisions and on job organization. The higher prevalence of stress-related symptoms among vicars was strongly modified by high work demands, in particular high quantitative demands. CONCLUSIONS: The higher prevalence of stress-related symptoms among vicars could largely be attributed to high-quantitative work demands.

Sickness absence in student nursing assistants following a preventive intervention programme.

BACKGROUND: We have previously shown that a multidimensional programme combining physical training, patient transfer techniques and stress management significantly reduced sickness absence rates in student nurse assistants (NAs) after 14 months of follow-up. At follow-up, the control group had reduced SF-36 scores for general health perception [general health (GH)], psychological well-being [mental health (MH)] and energy/fatigue [vitality (VT)] compared with the intervention group, which remained at the baseline level for all three measures. AIMS: To ascertain whether this effect remained after a further 36 months of follow-up and to analyse the association of GH, MH and VT scores with sickness absence. METHODS: This was a cluster randomized prospective study. The original study involved assessment at baseline and follow-up at 14 months (the duration of the student NA course). Of 568 subjects from the original intervention study, 306 (54%) completed a postal questionnaire at 36 months. RESULTS: Sickness absence increased in both groups between the first and second follow-up. At the second follow-up, the intervention group had a mean of 18 days of sickness absence compared with 25 in the control group but this was not significant. GH at 14 months follow-up was found to predict sickness absence levels after 3 years. MH and VT scores showed an inverse association with sickness absence but the results were not significant. CONCLUSIONS: The results suggest that the initial intervention did not have a sustained effect on sickness absence 36 months after initial follow-up of the study group.

Low triglycerides-high high-density lipoprotein cholesterol and risk of ischemic heart disease.

BACKGROUND: A high triglyceride (TG)--low high-density lipoprotein cholesterol (HDL-C) level (TG > or =1.60 mmol/L [> or =142 mg/dL] and HDL-C < or =1.18 mmol/L [< or =46 mg/dL]) is associated with a high risk of ischemic heart disease (IHD), whereas a low TG--high HDL-C level (TG < or =1.09 [< or =97 mg/dL] and HDL-C > or =1.48 mmol/L [> or =57 mg/dL]) is associated with a low risk. Conventional risk factors tend to coexist with high TG--low HDL-C levels. We tested the hypothesis that subjects with conventional risk factors would still have a low risk of IHD if they had low TG--high HDL-C levels. METHODS: Observational cohort study of 2906 men aged 53 to 74 years free of IHD at baseline. RESULTS: During 8 years, 229 subjects developed IHD. Stratified by conventional risk factors-low-density lipoprotein cholesterol level (< or =4.40 mmol/L or >4.40 mmol/L [< or =170 mg/dL or >170 mg/dL] [median value]), hypertensive status (blood pressure >150/100 mm Hg or taking medication), level of physical activity (>4 h/wk or < or =4 h/wk), and smoking status (nonsmokers vs smokers)-the incidence in men with high TG--low HDL-C levels was 9.8% to 12.2% in the low-risk and 12.2% to 16.4% in the high-risk strata; the corresponding values in men with low TG--high HDL-C concentrations were 4.0% to 5.1% and 3.7% to 5.3%, respectively. Based on an estimate of attributable risk, 35% of IHD might have been prevented if all subjects had had low TG--high HDL-C levels. CONCLUSION: Men with conventional risk factors for IHD have a low risk of IHD if they have low TG--high HDL-C levels.

High triglycerides and low HDL cholesterol and blood pressure and risk of ischemic heart disease.

Treatment of high blood pressure (BP) has not produced the expected reduction in risk of ischemic heart disease (IHD). Subjects with high BP often have the metabolic syndrome X, an aggregation of abnormalities in glucose and lipid metabolism. We tested the hypothesis that the BP level would be less predictive of risk of IHD in those with high triglycerides (TG) and low HDL cholesterol (HDL-C), the characteristic dyslipidemia in the metabolic syndrome than in those without. Baseline measurements of fasting lipids, systolic BP (SBP), diastolic BP (DBP), and other risk factors were obtained in 2906 men, age 53 to 74 years, free of overt cardiovascular disease. High TG/low HDL-C was defined as TG >1.59 mmol/L and HDL-C <1.18 mmol/L. Within an 8-year period, 229 men developed IHD. In men with high TG/low HDL-C, the incidence of IHD according to SBP (<120, 120 to 140, >140 mm Hg) was 12.5%, 12.9%, and 10.0% (P=NS), respectively, and according to DBP, the incidence of IHD was (<75, 75 to 90, >90 mm Hg) 13.7%, 10.6%, and 13.7% (P=NS), respectively. The corresponding figures for other men were 5.2%, 8. 0%, and 9.7% for SBP (P<0.001), and 6.1%, 7.5%, and 9.9% for DBP (P<0.03). In conclusion, the BP level did not predict the risk of IHD in those with high TG/low HDL-C. This finding may explain the reason lowering BP has not produced the expected reduction in IHD.

Headache and cognitive dysfunctions in snorers. A cross-sectional study of 3323 men aged 54 to 74 years: the Copenhagen Male Study.

OBJECTIVE: Cognitive symptoms, headache, and sleep-related complaints, including snoring, are commonly reported by patients with sleep apnea. Because patients with sleep apnea generally are snorers, we decided to study whether snoring per se is associated with cognitive complaints and headache. DESIGN: Cross-sectional epidemiologic follow-up study. SETTING: General community. PARTICIPANTS: A total of 3323 men, aged 54 to 74 years, previously selected from among employees of public or private companies in the Copenhagen, Denmark, area. METHOD: Participants were classified according to self-reported snoring habits and these were compared with self-reported cognitive complaints and headache. Fourteen potential confounders were included. RESULTS: The odds ratio (95% confidence interval) for headache was 1.5 (1.3 to 1.8, P < .0001) for self-reported snorers after adjustments for age, body mass index, and alcohol and tobacco consumption, whereas no relationships were found between snoring and memory or concentration problems in the total population. Snoring was not related to use of central nervous system medication; previous stroke; presence of parkinsonism, epilepsy, or psychiatric diseases; previous head trauma; or exposure to organic solvents. Hypersomnia was significantly associated with snoring (P < .0001), headache (P < .0001), memory problems (P < .0001), concentration problems (P < .0001), age (P < .01), body mass index (P < .001), and alcohol consumption (P < .05) and negatively correlated with smoking (P < .0001). Irrespective of the severity of hypersomnia, no association was found between snoring and memory or concentration problems. The relationship between snoring and headache was independent of severity of hypersomnia. CONCLUSIONS: Snoring is associated with headache but not with cognitive dysfunction. Hypersomnia shows a correlation to cognitive problems. If associations are found between snoring and cognitive dysfunction, these may be related in part to the presence of hypersomnia.

Are social inequalities as associated with the risk of ischaemic heart disease a result of psychosocial working conditions?

Large social inequalities exist in the risk of ischaemic heart disease (IHD), and they are only partly explained by established cardiovascular disease risk factors. Social class differences in psychosocial working conditions could be important explanatory factors. In a cohort of 1752 employed males, age in years, mean (S.D.): 59.7 (3.5), we investigated the issue. Self-reported psychosocial working conditions examined were: influence on the job, work monotony, work pace, degree of satisfaction with immediate superiors and colleagues, and ability to relax after working hours. One hundred and fourteen men were excluded due to prevalent cardiovascular disease. During the follow-up period (1985/86-1989), 46 men (approx. 3%) suffered an IHD event, 11 events were fatal. Compared with the rest, the highest social class had a relative risk with 95% CI (RR) of IHD of 0.26 (0.06-1.09), an association which was not explained by major potentially confounding or effect modifying factors: smoking, alcohol, physical activity, blood pressure, hypertension, body mass index, serum cholesterol, serum triglycerides, serum HDL, and serum selenium. Including psychosocial factors in the multivariate model had little influence on the estimate, RR = 0.21 (0.05-0.95), and yet there were highly significant differences in psychosocial working conditions between social classes. Neither self-reported influence on the job, work monotony, work pace, degree of satisfaction with immediate superiors and colleagues, nor interactions of the above factors were significantly associated with risk of IHD. However, men who reported that they were incapable of relaxing after working hours had a highly significant approximately threefold increased risk of IHD. We conclude that in middle-aged and elderly males self-reported, i.e. subjective psychosocial working conditions, did not contribute to the explanation of social inequalities in IHD, and that self-reported incapability to relax after work was associated with an increased risk of IHD.

Do physical and chemical working conditions explain the association of social class with ischaemic heart disease?

The aim of this study was to examine whether physical and chemical working conditions explain the association of social class with ischaemic heart disease (IHD). We investigated the issue in a cohort of 2974 males aged 53-75 years (mean 63) free from overt cardiovascular disease. Potential confounders included were: alcohol consumption, physical activity, tobacco smoking, serum cotinine, serum lipids, serum selenium, body mass index, blood pressure, hypertension, social class, and retirement status. During the follow-up period (1985-1986 to 31 December 1991), 184 men (6.2%) had a first IHD event; 44 events were fatal. Compared to higher social classes (classes I, II and III), lower classes (classes IV and V) had a significantly increased risk of IHD (P < 0.05); the age-adjusted relative risk (RR) with 95% confidence limits was 1.44 (1.06-1.95), P = 0.02. Mean who had been occupationally long-term exposed (> or = 5 years) to either soldering fumes or organic solvents had a significantly higher risk of IHD than unexposed: RRs were 2.1 and 1.7, respectively. After adjustment for all the above potential confounders and including also these two occupational factors, the RR of low social classes was reduced to a non-significant 1.24 (0.87-1.76), P = 0.24, i.e. by 45%. Adjusting for non-occupational factors only reduced the RR from 1.44 to 1.38 (1.0-1.90), P = 0.05, i.e. by about 14%. Assuming that the association of soldering fumes and organic solvents with risk of IHD was causal, it was estimated that 16% of IHD cases in low social class could be ascribed to these exposures.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum selenium concentration and risk of ischaemic heart disease in a prospective cohort study of 3000 males.

Whether an association, causative or not, exists between the level of serum selenium and the risk of ischaemic heart disease (IHD) remains unsettled. We investigated the issue in a cohort of 3387 males aged 53-74 years (mean 63). Based on information about health status, life-style and socioeconomic factors given in a prefilled comprehensive questionnaire, the men were interviewed and the information validated. Following the interview, they underwent a clinical examination and had a venous blood sample drawn for the determination of a number of biochemical characteristics. Three hundred and forty-six men were excluded due to prevalent cardiovascular disease, including stroke. During the next three years (1986-1989) 107 men (approximately 3%) suffered an IHD event; 25 events were fatal. Compared to others, men with serum selenium levels less than or equal to 1 mumol/l, approximately the lowest tertile, had a 70% increased risk of IHD, relative risk (RR) with 95% confidence limits was 1.70 (1.14-2.53). After multivariate adjustment for cholesterol, social class, smoking and age, RR was 1.55 (1.00-2.39). Serum selenium level was significantly (P less than 0.05), but not strongly, correlated with a number of IHD risk factors: serum cotinine, tobacco smoking, social class, alcohol consumption, total cholesterol, hypertension, age and physical inactivity. Body mass index, HDL-cholesterol and triglycerides were not significantly associated with serum selenium. We conclude that middle-aged and elderly Danish men with serum selenium less than or equal to 1 mumol/l had a significantly increased risk of ischaemic heart disease. This association was not explained by the interrelationship of serum selenium and major cardiovascular risk factors.

Cognitive function and snoring.

The relationship between self-reported snoring, headache and cognitive complaints (memory and concentration problems) was evaluated in an epidemiologic survey including 3,323 males, with a mean age of 63 (53-75) years. Fourteen potential confounders were examined. A strong association between snoring and headache was found, persisting after correction for potential confounders. An association was found between snoring and cognitive complaints only in those who reported good sleep quality without insomnia.

Snoring, family history, and genetic markers in men. The Copenhagen Male Study.

BACKGROUND: No studies have attempted to examine the genetic influence on the habit of snoring. The aim of the present study was to examine whether an association existed between self-reported snoring and family history of snoring and a number of genetic markers. MATERIAL AND METHODS: The data were derived from a primarily cardiovascular disease cohort study of 3,387 men aged 54 to 74 years. A number of sleep-related questions were included. Some 3,308 men had given valid questionnaire information on snoring and whether they had their own bedroom due to snoring and were regarded eligible for the present study. Men who reported that they snored often or always were considered habitual snorers, and those who reported that they seldom or never snored were considered nonsnorers. We considered habitual snorers who reported that they had their own bedroom due to snoring to be a group with a presumably more severe form of snoring. Information about other health and lifestyle parameters was obtained from a comprehensive questionnaire. Four major blood groups were determined: ABO, Rhesus, MNS, and Lewis, together with complement C3. A saliva sample was taken for determination of ABH secretor status. RESULTS: There was a strong relationship between habitual snoring and family history of snoring among grandparents, parents, siblings, and children. Odds ratios were from 2.4 to 4.2, and all associations were significant (p < 0.05). In multivariable analysis, the factor which most strongly separated habitual snorers from nonsnorers, was self-reported habitual snoring among family members. Looking at habitual snorers only, the factors most strongly separating those with their own bedroom due to snoring from those without, were the Lewis blood group phenotype, Le(a+b-) (29.6 vs 18.8%; p < 0.001; age, 63.4 vs 62.1 years; p < 0.01), and selfreported family history of habitual snoring (35.2 vs 29.0%; p < 0.05). CONCLUSION: There was an overall strong association between habitual snoring and family history of snoring. Among habitual snorers, two genetic markers and age, were the only factors that separated men who had their own bedroom due to snoring from others. The results of this study indicate that snoring, to some extent, is hereditary.

Risk of ischemic heart disease in self-reported snorers. A prospective study of 2,937 men aged 54 to 74 years: the Copenhagen Male Study.

Former studies have demonstrated an association between habitual snoring and cardiovascular morbidity and mortality. Control for the influence of potential confounders has been inadequate. To further elucidate the issue, we examined the association between snoring and future risk of ischemic heart disease (IHD) while controlling for a number of major cardiovascular risk factors and potential effect modifiers. Some 2,937 men without overt cardiovascular disease, aged 54 to 74 y (mean = 63 years), were classified according to snoring habits and followed up prospectively during 6 years (1985 to 1991). Potential cardiovascular disease risk factors included in the study were as follows: smoking, alcohol consumption, physical activity, hypertension, blood pressure, body mass index (BMI) (kg x m-2), social class, and serum concentrations of selenium, cotinine, total cholesterol, high-density lipoprotein cholesterol, and triglycerides. During the 6-year follow-up period, 182 men (6.2%) had an IHD event (42 were fatal), and 274 men died from all causes (9.3%). There was no difference in the prevalence of snorers among those who had an IHD event and those who did not during the follow-up period, 49.9% vs 50.5%, respectively. Among the younger half of the cohort (54 to 63 years), the age-adjusted incidence of IHD was slightly but not significantly increased in snorers, relative risk (RR) = 1.2 (0.8 to 1.9). When adjustments were made for relevant confounders--use of tobacco, alcohol consumption, and BMI--the RR dropped to 1.0 (0.6 to 1.6). Among the older half (64 to 74 years), there was no increased risk in snorers, RR = 1.0 (0.7 to 1.6). We conclude that there was a slightly increased risk that did not reach statistical significance of IHD in snorers. After multivariate adjustment, snoring was not associated with risk of IHD in middle-aged and elderly men.

Cardiovascular risk factors in snorers. A cross-sectional study of 3,323 men aged 54 to 74 years: the Copenhagen Male Study.

Former studies on the association between snoring and cardiovascular disease (CVD) have only partly taken established CVD risk factors into consideration. In the Copenhagen Male Study, 3,323 men aged 54 to 74 years were classified according to self-reported snoring habits. Eleven CVD risk factors were examined. The prevalence of snoring decreased with age, with a 50 percent higher frequency of snorers among the youngest quintile than among the oldest (p < 0.00001). Snoring, age adjusted, was positively associated with tobacco smoking (p < 0.001), alcohol consumption (p < 0.001), body mass index (BMI) (p < 0.0001), serum triglyceride level (p < 0.01), systolic blood pressure (p < 0.05) and nearly significantly associated with diastolic blood pressure (p = 0.07). Snorers were less physically active in leisure time than others (p < 0.01). The association between self-reported snoring and blood pressure disappeared when other factors, including BMI, were taken into consideration. No significant associations were found between snoring and social class, snoring and low- or high-density lipoprotein or between snoring and hypertension. We conclude that snoring is associated with major cardiovascular risk factors. Accordingly, it is evident that in studies on snoring and CVD, proper controlling for the influence of potential confounders is a sine qua non.

No evidence for altered cellular immune functions in personnel deployed in the Persian Gulf during and after the Gulf War--The Danish Gulf War study.

Veterans who have participated in the Gulf War suffer from a number of symptoms, collectively referred to as the Gulf War Syndrome. It has been hypothesized that a change in the systemic cytokine balance or other changes in immunological parameters could be responsible for some of the symptoms. We analyzed the peripheral blood natural killer (NK) cell activity of 686 Gulf War personnel who had been present in the Persian Gulf area during and immediately after the Gulf War as well as 231 gender and age-matched controls. The test material included individual samples of frozen peripheral blood mononuclear cells kept at -139 degrees C for a period of 50 to 380 days prior to NK cell analysis of freshly thawed cells. Significant differences in NK-cell activity were not observed by direct comparison of the levels of natural cytotoxic activity in the two groups. However, NK-cell cytotoxicity as such decreased due to cryopreservation. Surprisingly, the NK cells obtained from control donors were significantly (p<0.0001) more sensitive to freezing conditions than cells from the Gulf War personnel, leaving the marginal comparison between the two groups untrustworthy, in particular because of the marked difference between the -139 degrees C storage times used for the two groups. Freshly thawed samples of peripheral blood T lymphocytes (CD2+ cells) from 109 randomly selected Gulf War personnel and 68 gender- and age-matched controls were stimulated for 3 days with phytohemagglutinin followed by 4 h activation by phorbol ester and ionomycin, and were stained for intracellular content of interleukin-2, -5, -10 and interferon-gamma. As with natural cytotoxicity, the length of cell storage at -139 degrees C influenced the production of cytokines. No significant differences in the cytokine production between the two groups were observed when the influence of the storage period was taken into consideration. Together, these data suggest that no overall long-term effects on NK-cell function and T-cell cytokine production are present in the Danish Gulf War personnel. Moreover, cryopreservation is a major potential source of bias when studying the physiology of thawed NK and T cells.

Self-assessed job satisfaction and ischaemic heart disease mortality: a 10-year follow-up of urban bus drivers.

Several studies have shown that bus driving is a high-risk occupation for ischaemic heart disease (IHD). In order to study contributing factors in the job, all male full-time bus drivers in the three major cities in Denmark were followed for 10 years. It was hypothesized that bus drivers who reported job strain and job dissatisfaction would have an excess risk of subsequent death due to IHD. Of 2465 bus drivers, 2045 (83%) responded to a questionnaire distributed in 1978 on psychosocial well-being and work conditions. The men had their mortality recorded during the years 1978-1988. Information on causes of death was obtained from the Danish Register of Causes of Death. Some 212 respondents died during the follow-up period, 59 from IHD. Relative risk (RR) for death due to IHD and all other causes of death was calculated. As expected, we found a significantly increased risk of IHD in bus drivers working in a high traffic intensity area, RR = 1.6. In contrast to what was expected, men who reported a high degree of job satisfaction had increased risk of IHD. Those who did not look for another job had a highly significant sixfold increased risk of future death from IHD. Also those who reported never experiencing mental exhaustion after work, that their job was very varied, that their job was something special, and those who reported that they would choose the same job again, had an excess risk. Death due to other causes was positively associated with marital status only. We suggest that inconsistencies in the literature on self-assessed job strain and risk of IHD may be partly explained by the fact that studies in general have focused on absence or presence of the psychosocial factor in question. A more differentiated assessment of exposure might prove more useful.

Serum validated tobacco use and social inequalities in risk of ischaemic heart disease.

BACKGROUND: We have previously shown that the inverse social gradient in risk of ischaemic heart disease (IHD) was not explained by self-reported smoking habits. We pursued the issue in a follow-up study 15 years later, where use of tobacco was validated by serum cotinine. METHODS: Some 3216 men aged 53-75 years were included in a study on the association between self-reported tobacco use and serum cotinine concentration. The men had their morbidity and mortality recorded over 4 years. Some 2833 men without overt cardiovascular disease were included in the incidence study. Potential confounders examined were serum lipids, serum selenium, alcohol consumption, physical activity, hypertension, blood pressure, and body mass index. RESULTS: There was a strong positive correlation between serum cotinine level and self-reported tobacco smoking: r = 0.68, P < 0.0001. The misclassification rate of smokers as non-smokers was apparently higher in low social class. However, a larger proportion of men in low social class were users of chewing tobacco or snuff, and, when taking this into account, there was no social gradient (i.e. trend) in the estimated misclassification rates from social class I to social class V: 1.0%, 3.8%, 3.2%, 2.0%, 2.3%, P = NS. After validation of use of tobacco with serum cotinine measurements, compared with social class I, social class V had an overall significantly increased risk of IHD, relative risk = 4.5 (95% confidence interval: 1.6-12.9), P < 0.01, which was slightly higher than when no validation was performed. CONCLUSIONS: We conclude that, (i) social differences in use of tobacco validated by measurements of serum cotinine did not account for social inequalities in risk of IHD in middle-aged and elderly men, (ii) no significant social differences existed in the misclassification of smokers as non-smokers, (iii) reclassification of self-reported non-smokers should not be done without due consideration of the use of chewing tobacco and snuff.

Mortality and morbidity of potentially misclassified smokers.

OBJECTIVE: Misclassification of smokers as non-smokers may bias estimates of the excess morbidity and mortality associated with smoking. The issue has been given little, if any, attention in prospective epidemiological studies. This study examined characteristics of potentially misclassified smokers with respect to mortality, morbidity, and risk factors. METHOD: A prospective study (within The Copenhagen Male Study, Denmark) used serum cotinine as an objective marker of use of tobacco. A serum concentration of 100 ng/ml was regarded as a relevant threshold for active smoking. In all, 3270 males aged 53-74 years who reported their previous and current tobacco habits, including the use of chew tobacco and snuff, were included. Incidence of all causes of mortality (ACM) during 9 years and death due to ischaemic heart disease (IHD) during 8 years of follow-up were the main outcome measures. RESULTS: Overall cumulative incidence rates of ACM and IHD were 19.1% and 4.3%, respectively. Of 1405 men who reported being non-tobacco users, i.e. no current smoking and no use of chewing tobacco or snuff, 1377 had levels < 100 ng/ml, 28 men (2%) had levels equal to or above this threshold value and were considered potentially misclassified smokers. They had significantly higher mortality rates, 35.7% versus 14.7%, P < 0.001, than other self-reported non-tobacco users, and a slightly higher prevalence of tobacco-related cancer, and a highly significant higher prevalence of myocardial infarction, P < 0.001. Compared to non-tobacco users with low cotinine, age-adjusted relative risks (95% CI) were 2.4 (1.3-4.5), P < 0.01, for ACM, and 5.3 (95% CI : 2.1-13.4), P < 0.001, for IHD. CONCLUSIONS: Potentially misclassified smokers deviated strongly from other non-smokers with respect to mortality and morbidity. The importance of this reporting bias when estimating the risk associated with active or passive smoking is discussed.

Strong mediators of social inequalities in risk of ischaemic heart disease: a six-year follow-up in the Copenhagen Male Study.

OBJECTIVE: Large social inequalities exist in risk of ischaemic heart disease (IHD) in Western populations; inequalities which are only little accounted for by established risk factors. We wished to find out if some newly identified cardiovascular risk factors in concert with established factors might contribute further to the explanation. DESIGN AND SETTING: A 6-year follow-up in the Copenhagen Male Study. SUBJECTS: Some 2974 males aged 53-75 years (mean 63) without overt cardiovascular disease were included in the study. Potential confounders included were: alcohol, physical activity, smoking, serum lipids, serum cotinine, serum selenium, lifetime occupational exposure to soldering fumes and organic solvents, body mass index, blood pressure, hypertension, use of sugar in hot beverages, use of diuretics, and Lewis phenotypes. MAIN OUTCOME MEASURES: During the 6-year follow-up period (1985/1986-1991), 184 men (6.2%) had a first IHD event. Compared to higher social classes (classes I, II and III), lower classes (classes IV and V) had a significantly (P < 0.05) increased risk of IHD; age-adjusted relative risk (RR) with 95% confidence limits was 1.44 (1.1-1.9), P = 0.02. After multivariate adjustment for age, blood pressure, serum lipids, physical activity, and smoking, the RR dropped to 1.38 (1.0-1.9), P = 0.05. Some newly identified risk factors were significantly associated with increased risk of IHD as well as with low social class: a low serum selenium concentration, a low level of leisure time physical activity in midlife, long-term exposure to soldering fumes, and abstention from or a low consumption of wine and strong spirits. After adjustment for these factors also, the RR dropped to 1.12 (P = 0.54). CONCLUSIONS: The results of this study suggest that potentially modifiable risk factors associated with lifestyle and working environment are strong mediators of social inequalities in risk of ischaemic heart disease.

Socioeconomic status and ischaemic heart disease mortality in middle-aged men: importance of the duration of follow-up. The Copenhagen Male Study.

OBJECTIVES: The predictive value of some risk factors may diminish with increasing duration of follow-up. This study was performed to elucidate the role of socioeconomic status as a risk factor for ischaemic heart disease (IHD) mortality in middle-aged men, testing the hypothesis that the role of mediators of the association of socioeconomic status with risk of IHD would diminish with increasing length of follow-up. METHODS: A cohort of 5249 men aged 40-59 was established in 1971. Baseline data on social class and other confounder variables were collected, and the cohort was followed through registers for 8, 15, and 22 years. In all, 5028 without a history of myocardial infarction or angina pectoris were included in the follow-up. Four factors associated with either occupation or lifestyle were strong mediators of the association found between social class and risk of fatal IHD, and were more common in the lower social classes (classes IV and V): occasional demand for vigorous activity at work, low leisure time physical activity level, high alcohol consumption, and smoking. RESULTS: After the first 8 years, 78 men had died due to IHD, after 15 years: 222, and after 22 years: 411. Compared with social classes I, II, and III, the age-adjusted relative risk (RR) with 95% CI for classes IV and V was 1.69, P < 0.05 after the first 8 years; adjusted for the above potential risk factors the RR dropped to 1.09, P = NS. Corresponding RR after 15 years were 1.67, P < 0.001 and 1.33, P = NS; and after 22 years, 1.59, P < 0.001 and 1.36, P < 0.05. CONCLUSIONS: Risk factors with an uneven social distribution related to occupation and lifestyle were strong mediators of the association of socioeconomic status with risk of IHD. A quite strong explanatory potential persisted but diminished with length of follow-up.