Twins, smoking and mortality: a 12-year prospective study of smoking-discordant twin pairs

Despite the increasing scientific evidence for a causal role of tobacco smoking in lung cancer and coronary heart disease, critics, several decades ago, put forward an alternative hypothesis. The constitutional hypothesis has stated that there are genetic or other common factors, which predispose both to smoking and disease, but that the two are not causally related. A critical test of this hypothesis is the study of disease in monozygotic (MZ) twin pairs in which one smokes and the other never has. Earlier twin studies found only small differences in the mortality of smoking and nonsmoking twins of discordant pairs. In the Finnish Twin Cohort, a population-based panel of adult like-sexed twin pairs, a questionnaire study carried in 1975 permitted identification of twin pairs discordant for cigarette smoking. The nonsmoking cotwins had never been regular smokers. The smoking twins were divided into 1278 current smokers [CS; 143 MZ and 598 dizygotic (DZ) males and 171 MZ and 585 DZ females] and 1210 former smokers (FS; 129 MZ and 408 DZ males and 113 MZ and 341 DZ females). Exposure to tobacco was much higher among males; over 25% of men smoked 20 or more cigarettes daily compared to less than 10% of women. Follow-up of mortality yielded data on time and cause of death. Analyzing on first deaths from concordant pairs, there were 13 deaths in the smokers of male CS MZ pairs and 1 death in the nonsmoking cotwins (relative risk = 13.0, P less than 0.01). Excess mortality was also found for male CS DZ smokers (RR = 2.43, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

The association between body height and coronary heart disease among Finnish twins and singletons

OBJECTIVE: An inverse association between body height and the incidence of coronary heart disease (CHD) has been observed. However, the mechanisms behind this association are still largely unknown. We will examine the role of genetic and familial factors behind the association in a large twin data set. DESIGN AND SETTING: The data were derived from the Finnish Twin cohort including 2438 singletons, 4073 monozygotic (MZ) twins, and 9202 dizygotic (DZ) twins aged 25-69 years at baseline in 1976. Incident CHD cases were derived from hospital discharge data and cause of death data between 1977 and 1995. Cox regression analysis and conditional logistic regression analysis were used. RESULTS: In population-level analyses no differences in the general risk of CHD between zygosity groups were found. The association between body height and CHD was similar between sexes and zygosity groups. When men and women in all zygosity groups were studied together an increased risk of CHD was found only among the shortest quartile (hazard ratio [HR] = 1.34, 95% CI: 1.14-1.57). Among the twin pairs discordant for CHD a suggestive increased risk for the shorter twin was seen among DZ twins (odds ratio [OR] = 1.19, 95% CI: 0.95-1.48) when men and women were studied together. CONCLUSION: An inverse association between body height and CHD was broadly similar between sexes and twin zygosity groups and was associated with short stature. Among discordant twin pairs we found a weak association among DZ twins but not MZ twins. This may suggest the role of genetic liability behind the association between body height and CHD.     

The heritability of smoking behaviour in pregnancy, and the birth weights of offspring of smoking-discordant twins

Questionnaire information on smoking habits in pregnancy was collated in 341 monozygotic (MZ) and 321 dizygotic (DZ) female twin pair cases from a population-based Norwegian Twin Panel. In a multifactorial model, the intra-pair correlation in smoking was 0.797 (+/- 0.042) in monozygotic (MZ) and 0.443 (+/- 0.075) in dizygotic (DZ) twin pairs, indicating a substantial genetic influence on liability to smoke in pregnancy. The questionnaire information was linked with birth records in the Medical Birth Registry of Norway, and birth weights of offspring of 62 MZ and 100 DZ smoking-discordant twin pairs were studied. Offspring of smoking MZ twins weighed 127 g less than birth order matched offspring of the non-smoking co-twins. This finding is additional evidence that smoking is a direct cause of reduced birth weight in offspring.     

Genetic and developmental influences on susceptibility to epilepsy: evidence from twins

This study evaluated genetic and developmental contributions to epilepsy, using data on epilepsy and multiple births in the sibships of 1981 probands with epilepsy. Prevalence of a history of epilepsy was much higher in monozygotic (MZ) than in dizygotic (DZ) co-twins of probands (35.0% vs. 3.7%), but prevalence was not significantly higher in DZ co-twins than in singleton siblings. The proportion of individuals who were MZ twins was higher among probands with epilepsy than among their non-co-twin siblings without epilepsy (odds ratio 2.5, 95% CI 1.31-4.85). However, the proportion who were DZ twins was similar among probands and unaffected siblings (odds ratio 1.0, 95% CI 0.67-1.60). These findings suggest that the increased prevalence of epilepsy in MZ co-twins of probands may be partly explained by developmental factors related to MZ twinning, rather than by their genetic identity with the probands.     

Cancer incidence in urban bus drivers and tramway employees: a retrospective cohort study

OBJECTIVE: To investigate the risk of cancer associated with exposure to air pollution among bus drivers and tramway employees. METHODS: A retrospective cohort study of 18,174 bus drivers or tramway employees in Copenhagen in the period 1900-94. Data on employment were obtained from company files. Information on cancer was obtained from the Danish Cancer Registry. RESULTS: Findings showed that bus drivers or tramway employees had an increased risk of all malignant neoplasms (standardised incidence ratio (SIR) 1.24, 95% confidence interval (95% CI) 1.19 to 1.30). The relative risk was significantly increased for both men and women (SIR 1.24, 95% CI 1.19 to 1.30 and 1.28, 1.06 to 1.53, respectively). People employed for < 3 months had no increased risk of cancer (1.04, 0.81 to 1.31). For men who were employed for > 3 months the risk of lung cancer (1.6, 1.5 to 1.8), laryngeal cancer (1.4, 1.0 to 1.9), kidney cancer (1.6, 1.3 to 2.0), bladder cancer (1.4, 1.2 to 1.6), skin cancer (1.1, 1.0 to 1.2), pharyngeal cancer (1.9, 1.2 to 2.8), rectal cancer (1.2, 1.0 to 1.5) and liver cancer (1.6, 1.2 to 2.2) was significantly increased. For women employed for > 3 months the risk of lung cancer was significantly increased (2.6, 1.5 to 4.3). CONCLUSION: This cohort study shows that bus drivers and tramway employees are at an increased risk of developing several types of cancer. This might be due to the exposure to air pollution during working hours or to other risk factors, primarily smoking.     

Lifestyle factors in monozygotic and dizygotic twins

In examining genetic influences on biological variables using twins, it may be important to examine the distribution between and within twin pairs of demographic and lifestyle factors that may themselves affect the biological variable being studied. We explored the distribution of demographic and lifestyle factors that may affect blood lipid levels or ischaemic heart disease (IHD) risk among a sample of 106 monozygotic (MZ) and 94 like-sex dizygotic (DZ) twin pairs. In our sample, MZ twins were statistically significantly different from DZ twins only in marital status, cigarette smoking habits, and the ratio of polyunsaturated to saturated fat (P:S ratio) in their dietary intake. The latter variable was among many dietary variables examined (using 4-day weighed food diaries), and the size of the difference in intake was small. When comparisons were made of the similarities within twin pairs, we found members of MZ twin pairs to be statistically significantly closer than DZ twins in educational achievement, occupation, cigarette smoking, and exercise habits, and the number of days a week on which alcohol was consumed. These last three variables were consistently closer among twins with closer contact than among those with a smaller degree of current shared environment. For 12 of the 13 nutrients examined, the within-pair correlations were higher for MZ than for DZ twins, although our test for significant genetic variance showed statistical significance only for intake of complex carbohydrates. We conclude that MZ twins share demographic and lifestyle factors that might influence the risk of IHD and blood lipid levels to a greater degree than do DZ twins, although it is difficult to say if these similarities in lifestyle result from genetic influences or not. Nevertheless, ascribing differences between correlations in MZ and DZ twin pairs for lipid levels as being purely "genetic"--as implicit in conventional measures of heritability--is likely to overestimate the influence of genetic factors.     

Modest associations between self-reported physical workload and neck trouble: a population-based twin control study

Objectives

To investigate the relationship between self-reported physical workload and neck trouble (NT) in twins. Additionally, to explore whether the relationship between physical workload and NT is influenced by genetic factors.

Methods

A twin control study was performed within a population-based, cross-sectional questionnaire study using 3,208 monozygotic (MZ) and same-sexed dizygotic (DZ) twins aged 19–70. Twin pairs discordant for self-reported NT during the past year (“Any NT”) were included. Self-reported physical workload in four categories was used as exposure (“sitting,” “sitting and walking,” “light physical,” and “heavy physical” work). Paired analyses including conditional logistic regression were made for all participants and for each sex, and MZ and DZ pairs separately.

Results

No marked associations between physical workload and NT were seen. A moderate risk elevation in “heavy physical” work was seen in DZ men (odds ratio 2.3, 95 % confidence intervals 1.3–4.0), but not in MZ men or the MZ or DZ women.

Conclusions

The findings in some degree supported that “heavy physical” work is a determinant of NT, perhaps only in men, but hardly of any greater importance. The different results between DZ and MZ men suggest that genetic factors influence the relationship between physical workload and NT.     

Concordance for mortality with special reference to ischaemic heart disease and cerebrovascular disease: A Study on the Swedish Twin Registry

The Swedish Twin Registry contains about 11 000 same-sexed twin pairs born between 1886 and 1925 with both members alive when the registry was formed in 1961. During the years 1962 to 1973, 2780 deaths occurred. 727 deaths were due to ischaemic heart disease (IHD), 345 due to cerebrovascular disease (CVD), and 727 due to cancer. The rate of concordance for the whole twin population revealed a significantly (p < 0.05) higher concordance rate for IHD among the male monozygotic (MZ) pairs as compared to the dizygotic (DZ) pairs (15.8% versus 8.0%). The corresponding figures for the female pairs were 11.0% (MZ) and 7.5% (DZ), respectively. With regard to death in CVD and cancer, the rates of concordance were about the same for MZ and DZ pairs in both males and females. When subgrouping was made for age groups, the difference in concordance rate for IHD in males was still more pronounced for the younger age group, born 1901–1925, (16.1% versus 5.4%). These data may indicate the existence of a genetic determination on death in IHD, especially in males, whereas a genetic determination on death in CVD and cancer seems more uncertain.     

Accuracy of self-reported anthropometric measures — Findings from the Finnish Twin Study

ObjectiveTo determine the accuracy of self-reported height, weight, body mass index (BMI) and waist circumference (WC) compared to the measured values, and to assess the similarity between self-reported and measured values within dizygotic (DZ) and monozygotic (MZ) twin pairs.MethodsThe data on self-reported and measured height, weight and WC values as well as measured hip circumference (HC) were collected from 444 twin individuals (53–67 years old, 60% women). Accuracies between self-reported and measured values were assessed by Pearson’s correlation coefficients, Cohen’s kappa coefficients and Bland-Altman 95% limits of agreement. Intra-class correlation was used in within-pair analyses.ResultsThe correlations between self-reported and measured values were high for all variables (r = 0.86–0.98), although the agreement assessed by Bland-Altman 95% limits had relatively wide variation. The degree of overestimating height was similar in both sexes, whereas women tended to underestimate and men overestimate their weight. Cohen’s kappa coefficients between self-reported and measured BMI categories were high: 0.71 in men and 0.70 in women. Further, the mean self-reported WC was less than the mean measured WC (difference in men 2.5 cm and women 2.6 cm). The within-pair correlations indicated a tendency of MZ co-twins to report anthropometric measures more similarly than DZ co-twins.ConclusionsSelf-reported anthropometric measures are reasonably accurate indicators for obesity in large cohort studies. However, the possibility of more similar reporting among MZ pairs should be taken into account in twin studies exploring the heritability of different phenotypes.     

Should years of schooling be used to guide treatment of coronary risk factors?

PURPOSE: We wanted to compare the risk of death from coronary heart disease (CHD) for patients of low socioeconomic status, measured by educational level, with established risk factors. METHODS: We undertook a prospective cohort study. Participants included a representative sample of 6,479 adults aged 25 to 74 years in the United States who were free of CHD at enrollment in the first National Health and Nutrition Examination Survey (NHANES I). RESULTS: Baseline measures included years of education, age, sex, systolic blood pressure, diabetes, total cholesterol level, and smoking. Outcome was death within 10 years from CHD. The relative risk (RR) associated with less than 12 years of education compared with more than 12 years (RR 1.5; 95% confidence interval [CI], 1.2-1.8) was comparable to being male (RR 1.4; 95% CI, 1.2-1.6), smoking (RR 1.4; 95% CI, 1.1-1.6), having a total cholesterol level of greater than 280 mg/dL (RR 1.6; 95% CI, 0.9-2.7), and systolic blood pressure of 130-139 mm Hg (RR 1.6; 95% CI, 1.0-2.4). Findings were comparable for estimates of absolute risk. CONCLUSIONS: Low educational level is associated with comparable risk as established risk factors for CHD mortality. Incorporation of educational level into risk-based guidelines for treatment could potentially reduce socioeconomic disparities in CHD by lowering thresholds for treatment.     

Chronic hepatitis B virus infection and mortality from non-liver causes: results from the Haimen City cohort study

BACKGROUND: Studies of chronic hepatitis B virus (HBV) infection in endemic populations have rarely documented causes of mortality other than liver disease and hepatocellular carcinoma (HCC). METHODS: We analysed all-cause mortality related to HBV infection, focusing on the deaths not related to liver disease in a prospective cohort of adults living in Haimen City, China, who were followed from 1992 to 2002. Death certificate data from 4590 deaths among 83 794 individuals were analysed. At cohort entry, 15.0% of the 58 454 male subjects and 10.7% of 25 340 female subjects were hepatitis B surface antigen positive [HbsAg(+)]. HCC and chronic liver disease were the major causes of death in both men and women in this population. The analysis focused on non-liver causes of death. RESULTS: When liver-related causes of death were excluded, there was still a significantly higher age-adjusted death rate among HBsAg(+) individuals. The relative risks (RRs) and 95% confidence intervals (CIs) for all non-liver deaths among HBsAg(+) subjects were 1.2 (1.1-1.3) in men and 1.4 (1.1-1.7) in women. Non-liver causes were further subdivided into cancer and non-cancer groups. For all non-liver cancers, the RR was 1.2 (1.0-1.4) for males and 1.7 (1.2-2.3) for females. Non-liver, non-cancer deaths had RRs of 1.2 (1.1-1.4) and 1.2 (0.9-1.6) in males and females, respectively. CONCLUSIONS: HBV-infected individuals may be at increased mortality risk from non-liver causes. Possible reasons include a direct effect of HBV infection, changes in the host immune system as a cause or effect of chronic infection, and behavioural factors associated with HBV infection. Further studies are needed to confirm this finding.     

Concordance rates and modifiable risk factors for lower urinary tract symptoms in twins

INTRODUCTION: Lower urinary tract symptoms, which are common in older men, are thought to be determined genetically and by modifiable environmental risk factors. We examined the contribution of these 2 etiologic components in a cohort of U.S. twins. METHODS: In 1998, a questionnaire that assessed lower urinary tract symptoms, weight, height, alcohol consumption, cigarette smoking, and physical activity was sent out to members of the National Academy of Science-National Research Council Twins Registry. We analyzed 1,723 complete twin pairs with information on lower urinary tract symptoms and zygosity and who did not have a previous diagnosis of prostate cancer. We calculated concordance rates of categories of the International Prostate Symptom Score in monozygotic (MZ) and dizygotic (DZ) twins. Generalized estimating equations were used to calculate the odds ratio of having high-moderate/severe lower urinary tract symptoms. RESULTS: Concordance rates were higher in MZ than in DZ twins with concordance rate ratios of 2.2 and 6.9 depending on the specificity of definition of symptoms. Genetic factors contributed 72% to the risk of high-moderate/severe lower urinary tract symptoms. Taking into account correlated individuals, we observed high odds of lower urinary tract symptoms in obese men compared with lean men (odds ratio = 1.91; 95% confidence interval = 1.16-3.15 comparing first versus fourth quartile). Cigarette smoking was not associated with lower urinary tract symptoms, but alcohol consumption was positively associated. Men who were more physically active tended to have lower odds of lower urinary tract symptoms compared with less active men (0.62; 0.36-1.08). CONCLUSION: The findings indicate a strong genetic component of lower urinary tract symptoms, but also support previous studies that modifiable environmental risk factors are associated with this condition.     

Joint effect of cigarette smoking and alcohol consumption on mortality

OBJECTIVE: To evaluate the joint effect of cigarette smoking and alcohol consumption on mortality. METHODS: A population-based cohort of 66,743 Chinese men aged 30-89 in Shanghai, China recruited from 1996 to 2000. Lifestyle data were collected using structured questionnaires. As of November 2004, follow-up for the vital status of 64,515 men was completed and death information was further confirmed through record linkage with the Shanghai Vital Statistics Registry. Associations were evaluated by Cox regression analyses. RESULTS: 2514 deaths (982 from cancers, 776 from cardiovascular diseases (CVD)) were identified during 297,396 person-years of follow-up. Compared to never-smokers, both former and current smokers had significantly elevated mortality from any cause, CVD, and cancer; risk increased with amount of smoking. Intake of 1-7 drinks/week was associated with reduced risk of death, particularly CVD death (hazard ratio (HR): 0.7, 95% confidence interval (CI): 0.5, 1.0), whereas intake of >42 drinks/week was related to increased mortality, particularly cancer-related death (HR: 1.7, 95% CI: 1.1, 2.5). The HR for total mortality associated with moderate alcohol consumption increased from 0.8 (95% CI: 0.6, 1.0) for non-smokers to 1.0 (0.9, 1.2) for moderate smokers and 1.4 (95% CI: 1.2, 1.7) for heavy smokers. Heavy drinkers and heavy smokers had the highest mortality (HR: 1.9, 95% CI: 1.6, 2.4). CONCLUSIONS: Light and moderate alcohol consumption reduced mortality from CVD. This beneficial effect, however, was offset by cigarette smoking.     

Concordance of ischemic heart disease in the NHLBI twin study after 14-18 years of follow-up

Morbidity and mortality were assessed in the NHLBI twin study at the end of 1987. Deaths were greater in DZ twins (58/520, 11.2%) than MZ twins (38/508, 7.5%). Ischemic heart disease concordances were 2.3 times higher in MZ pairs and 2.8 times higher in DZ pairs than expected based on the prevalence of ischemic heart disease in the cohort. Family history scores for heart disease, calculated 14-18 years earlier at entry to the study, were significantly higher in DZ pairs where one or both members later developed ischemic heart disease and in corcordant MZ pairs than in twin-pairs without any subsequent heart disease. Concordance rates were not significantly different between MZ and DZ pairs. The results agree with previous suggestions that selection at enlistment into the armed services over 40 years ago, as well as later volunteering for the NHLBI twin study, resulted in a decline in the number of concordant MZ pairs.     

双生子A型人格与高血压及血生化指标研究

目的 了解双生子A型人格与高血压及血液生化指标的关系。方法 利用遗传流行病学方法对青岛市89对24岁以上双生子(同卵55对，异卵34对)进行调查。并进行A型人格测试，以比较同卵与异卵双生于A型人格得分的相关程度、A型人格及血压的一致性。推测遗传与环境因素对A型人格的影响，A型人格与高血压的关系，并探讨血液生化指标与A型人格的关系。结果 经KAPPA一致性检验，同卵(MZ)双生子之间A型人格存在着显的一致性(P＜0．001)，而异卵(DZ)双生子之间的一致性无显性差异(P＝0．802)。同时，MZ双生子之间A型人格和血压也存在显的一致性(P＜0．001)，而DZ双生子之间A型人格和血压无明显一致性(P＝0．102)。有A型人格的双生子血压的收缩压明显高于非A型人格的双生子(P＜0．05)。许多生化指标与A型人格因素相关，但是所计算出的相关系数大都小于0．30，属于弱相关。结论 MZ双生子A型人格及高血压之间存在着显的一致性，而这种一致性在DZ双生子表现不明显。A型人格是高血压的危险因素之一。A型人格与所研究血液基本生化指标之间相关较弱。     

Migration and mortality: a 20 year follow up of Finnish twin pairs with migrant co-twins in Sweden

STUDY OBJECTIVE: Finland has a higher mortality overall and for major causes of death than Sweden, primarily in men. The objective of this study was to analyse mortality in migrants from Finland to Sweden. DESIGN: A longitudinal study based on the Finnish Twin Cohort Study. Information about migration from Finland to Sweden, duration of stay in Sweden for the migrants, and deaths 1976-1995 was obtained from national registers. Observed numbers of deaths in migrants were compared with expected numbers based on the age standardised mortality experience of the Finnish Twin Cohort. First deaths in migrants and non-migrants of migrant discordant pairs were compared controlling for genetic and early childhood factors. PARTICIPANTS: Twin pairs of the Finnish Twin Cohort Study where at least one twin had migrated to Sweden (1542 twin pairs). MAIN RESULTS: Among men, migrants from Finland to Sweden showed an overall similar mortality compared with all subjects of the Finnish Twin Cohort (SMR 1.1; 95% CI 0.9 to 1.4). Mortality from non-violent causes was increased for migrants with at most 20 years in Sweden (SMR 1.9; 95% CI 1.2 to 2.6) and decreased in those with a longer stay (SMR 0.7; 95% CI 0.4 to 0.9). Similar results were obtained concerning first deaths in twin pairs discordant for migration. Among women, migrants had an increased mortality overall (SMR 1.4; 95% CI 1.0 to 1.8), from cardiovascular disease (SMR 1.7; 95% CI 1.0 to 2.7), and from violent causes (SMR 2.5; 95% CI 1.2 to 4.6) compared with all women of the Finnish Twin Cohort. In analyses of migrant discordant pairs only first deaths from cardiovascular disease tended to be more common in the migrants than in non-migrant co-twins. CONCLUSIONS: Migrants from Finland to Sweden seem to have an overall mortality comparable to that prevailing in Finland suggesting no strong influence on mortality by the migration. Duration of stay seems to be associated with mortality in the migrants, at least in men, with a lower mortality after several years in Sweden.     

Migration and coronary heart disease: A study of Finnish twins living in Sweden and their co-twins residing in Finland

BACKGROUND: Finland and Sweden are neighbouring countries with a substantially higher incidence and mortality from coronary heart disease (CHD) in Finland. Migration from Finland to Sweden has resulted in a population of about 187,000 Finnish immigrants, with a higher risk of CHD than Swedes. The aim of the present study was to analyse the prevalence of CHD in migrants to Sweden compared with co-twins remaining in Finland. METHODS: The study population consisted of twin pairs of the Finnish Twin Cohort Study where at least one twin had lived one year or more in Sweden, including 1,534 subjects and 251 complete twin pairs discordant regarding residency in Sweden. Emigrant twins were compared with nonmigrant co-twins regarding prevalence of CHD in 1998. CHD prevalence was assessed by self-reported questionnaires validated using information from a clinical examination. RESULTS: Self-reported CHD showed a good correspondence with clinical diagnosis. Differences in social and behavioural risk factors for CHD among men were small but emigrants were more physically active than non-migrants. Female emigrants had less overweight and better education, but were more often working class than non-migrants. Intra-pair comparisons restricted to migration discordant pairs showed a tendency towards a reduced prevalence of CHD in the migrant co-twins (0.6; 0.3-1.4). In analyses of all subjects disregarding pair status, emigrants showed a reduced prevalence of CHD compared with subjects always living in Finland (0.6; 0.4-0.9). CONCLUSION: Emigration from Finland to Sweden may be associated with a reduced prevalence of CHD. The causes are most likely multifactorial and may involve changes in dietary habits, physical activity, psychosocial factors, and inflammation.     

Clustering of high density lipoprotein cholesterol levels in premenopausal and postmenopausal female twins

Previous family and twin studies indicate that genetic variation makes an important contribution to individual variation in high density lipoprotein cholesterol (HDL) levels, even after adjustment for covariates (such as obesity and alcohol consumption) that also cluster in families. However, most studies assume that genetic mechanisms affecting variation in HDL level are the same in all subgroups of the population (e.g., men versus women, by age). Using data from the Kaiser-Permanente Women Twins Study, we found different patterns of clustering for monozygotic (MZ) and dizygotic (DZ) twins depending on menopausal status. Premenopausal MZ twins were more similar than postmenopausal MZ twins (r_i = 0.79 and r_i = 0.61, respectively, after adjustment for age, alcohol consumption, smoking status, degree of obesity, and leisure-time exercise); premenopausal and postmenopausal DZ twins were alike to the same extent (r_i = 0.31 and r_i = 0.32, respectively, adjusted as above). These data suggest that either postmenopausal MZ twins have a greater degree of shared environment than postmenopausal DZ twins (e.g., postmenopausal female hormone use) or that genetic mechanisms that affect individual variation in HDL level differ in pre- and postmenopausal women. Data were not available on postmenopausal female hormone use. If genetic mechanisms that influence variation in HDL levels differ between pre- and postmenopausal women, genetic epidemiologic methods that assume that genetic and environmental sources of variation are the same for all groups of individuals may lead to false conclusions. © 1993 Wiley-Liss, Inc.     

Psychosocial factors at work, smoking, sedentary behavior, and body mass index: a prevalence study among 6995 white collar workers

This cross-sectional study examined whether psychosocial factors at work were associated with smoking, sedentary behavior, and body mass index. The study population was composed of 3531 men and 3464 women employed as white collar workers in 21 organizations. Data were collected at worksites. Psychological demands and decision latitude at work were measured with the Karasek 18-item questionnaire. Smoking, sedentary behavior, and mean body mass index were compared by quartiles of decision latitude and psychological demands and by job strain categories. Prevalence of smoking, mean number of cigarettes smoked per day, prevalence of sedentary behavior, and mean body mass index were not consistently associated with decision latitude, psychological demands, or high job strain. However, prevalence of smoking was elevated in women belonging to the highest quartile of psychological demands (odds ratio [OR], 1.2; 95% confidence interval [CI], 1.0 to 1.6) and in the active job strain groups in both men (OR, 1.6; 95% CI, 1.2 to 2.1) and women (OR, 1.4; 95% CI, 1.0 to 2.0). Prevalence of sedentary behavior was elevated in men in the lowest quartile of decision latitude (OR, 1.3; 95% CI, 1.0 to 1.7), in the passive group (OR, 1.3; 95% CI, 1.0 to 1.5), and in the high strain group (OR, 1.2; 95% CI, 1.0 to 1.6). In women, this prevalence was elevated in the third quartile of psychological demand (OR, 1.3; 95% CI, 1.1 to 1.6). These results provide only partial support for an association between some psychosocial factors at work and the prevalence of smoking and sedentary behavior.