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1.  Job Strain as a Risk Factor for Leisure-Time Physical Inactivity: An Individual-Participant Meta-Analysis of Up to 170,000 Men and Women 
American Journal of Epidemiology  2012;176(12):1078-1089.
Unfavorable work characteristics, such as low job control and too high or too low job demands, have been suggested to increase the likelihood of physical inactivity during leisure time, but this has not been verified in large-scale studies. The authors combined individual-level data from 14 European cohort studies (baseline years from 1985–1988 to 2006–2008) to examine the association between unfavorable work characteristics and leisure-time physical inactivity in a total of 170,162 employees (50% women; mean age, 43.5 years). Of these employees, 56,735 were reexamined after 2–9 years. In cross-sectional analyses, the odds for physical inactivity were 26% higher (odds ratio = 1.26, 95% confidence interval: 1.15, 1.38) for employees with high-strain jobs (low control/high demands) and 21% higher (odds ratio = 1.21, 95% confidence interval: 1.11, 1.31) for those with passive jobs (low control/low demands) compared with employees in low-strain jobs (high control/low demands). In prospective analyses restricted to physically active participants, the odds of becoming physically inactive during follow-up were 21% and 20% higher for those with high-strain (odds ratio = 1.21, 95% confidence interval: 1.11, 1.32) and passive (odds ratio = 1.20, 95% confidence interval: 1.11, 1.30) jobs at baseline. These data suggest that unfavorable work characteristics may have a spillover effect on leisure-time physical activity.
doi:10.1093/aje/kws336
PMCID: PMC3521479  PMID: 23144364
cohort studies; exercise; physical activity; psychosocial factors; working population
2.  Childhood adversities and adult-onset asthma: a cohort study 
BMJ Open  2012;2(5):e001625.
Objectives
Childhood adversities may be important determinants of later illnesses and poor health behaviour. However, large-scale prospective studies on the associations between childhood adversities and the onset of asthma in adulthood are lacking.
Design
Prospective cohort study with 7-year follow-up.
Setting
Nationally representative study. Data were collected from the Health and Social Support (HeSSup) survey and national registers.
Participants
The participants represent the Finnish population from the following age groups: 20–24, 30–34, 40–44, and 50–54 years at baseline in 1998 (24 057 survey participants formed the final cohort of this study). The occurrence of childhood adversities was assessed at baseline with a six-item survey scale. The analyses were adjusted for sociodemographic characteristics, behavioural health risks and common mental disorders.
Primary and secondary outcomes
The survey data were linked to data from national health registers on incident asthma during a 7-year follow-up to define new-onset asthma cases with verified diagnoses.
Results
A total of 12 126 (59%) participants reported that they encountered a childhood adversity. Of them 3677 (18% of all) endured three to six adversities. During a follow-up of 7 years, 593 (2.9%) participants were diagnosed with incident asthma. Those who reported three or more childhood adversities had a 1.6-fold (95% CI 1.31 to 2.01) greater risk of asthma compared to those without childhood adversities. This hazard attenuated but remained statistically significant after adjustment for conventional risk factors (HR 1.33; 95% CI 1.06 to 1.67).
Conclusions
Adults who report having encountered adversities in childhood may have an increased risk of developing asthma.
doi:10.1136/bmjopen-2012-001625
PMCID: PMC3488721  PMID: 23069774
Psychiatry; Epidemiology
3.  Job strain as a risk factor for coronary heart disease: a collaborative meta-analysis of individual participant data 
Lancet  2012;380(9852):1491-1497.
Summary
Background
Published work assessing psychosocial stress (job strain) as a risk factor for coronary heart disease is inconsistent and subject to publication bias and reverse causation bias. We analysed the relation between job strain and coronary heart disease with a meta-analysis of published and unpublished studies.
Methods
We used individual records from 13 European cohort studies (1985–2006) of men and women without coronary heart disease who were employed at time of baseline assessment. We measured job strain with questions from validated job-content and demand-control questionnaires. We extracted data in two stages such that acquisition and harmonisation of job strain measure and covariables occurred before linkage to records for coronary heart disease. We defined incident coronary heart disease as the first non-fatal myocardial infarction or coronary death.
Findings
30 214 (15%) of 197 473 participants reported job strain. In 1·49 million person-years at risk (mean follow-up 7·5 years [SD 1·7]), we recorded 2358 events of incident coronary heart disease. After adjustment for sex and age, the hazard ratio for job strain versus no job strain was 1·23 (95% CI 1·10–1·37). This effect estimate was higher in published (1·43, 1·15–1·77) than unpublished (1·16, 1·02–1·32) studies. Hazard ratios were likewise raised in analyses addressing reverse causality by exclusion of events of coronary heart disease that occurred in the first 3 years (1·31, 1·15–1·48) and 5 years (1·30, 1·13–1·50) of follow-up. We noted an association between job strain and coronary heart disease for sex, age groups, socioeconomic strata, and region, and after adjustments for socioeconomic status, and lifestyle and conventional risk factors. The population attributable risk for job strain was 3·4%.
Interpretation
Our findings suggest that prevention of workplace stress might decrease disease incidence; however, this strategy would have a much smaller effect than would tackling of standard risk factors, such as smoking.
Funding
Finnish Work Environment Fund, the Academy of Finland, the Swedish Research Council for Working Life and Social Research, the German Social Accident Insurance, the Danish National Research Centre for the Working Environment, the BUPA Foundation, the Ministry of Social Affairs and Employment, the Medical Research Council, the Wellcome Trust, and the US National Institutes of Health.
doi:10.1016/S0140-6736(12)60994-5
PMCID: PMC3486012  PMID: 22981903
4.  Diurnal Evening Type is Associated with Current Smoking, Nicotine Dependence and Nicotine Intake in the Population Based National FINRISK 2007 Study 
Aims
To examine whether smoking habits, nicotine dependence (ND) and plasma cotinine levels differ by diurnal type.
Design
Data originated from the national FINRISK 2007 survey. Regression analyses were calculated to examine the association between diurnal type and smoking status, ND, and nicotine intake.
Participants
7091 FINRISK participants with smoking and diurnal type information and a subset of 1746 ever smokers with detailed smoking, and ND assessments.
Measurements
Diurnal type assessed with a six-item sum scale was categorized as morning, intermediate and evening type. Smoking status was determined as current (daily or occasional), former, and never smokers. ND was measured with the Fagerström Test for Nicotine Dependence (FTND), the Hooked on Nicotine Checklist (HONC), and the Nicotine Dependence Syndrome Scale (NDSS). For current smokers, plasma cotinine was analyzed as biochemical measurement of nicotine intake.
Findings
Evening type was associated with current smoking (OR=1.66, 95% CI 1.40, 1.97). A significant association with diurnal type was seen for FTND among men (beta= -0.46, 95% CI -0.72, -0.21), sexes combined for HONC (beta= -0.31, 95% CI -0.52, -0.11) and NDSS (beta= -0.86, 95% CI -1.43, -0.29) and for cotinine among men (beta= -0.73, 95% CI -1.16, -0.29). Adjustment for depressive symptoms attenuated the association of diurnal type with NDSS to be non-significant.
Conclusions
Diurnal type was associated with multiple ND measures and nicotine intake, interestingly more so among men. Evening type persons are at higher risk of dependence, but depressive symptoms attenuates this association clearly.
PMCID: PMC3422076  PMID: 22905332
Adults; Smoking; Nicotine dependence; Diurnal type; Chronotype; Eveningness; Fagerström test for nicotine dependence; Nicotine dependence syndrome scale; Hooked on nicotine checklist; Cotinine
5.  Job Strain and Tobacco Smoking: An Individual-Participant Data Meta-Analysis of 166 130 Adults in 15 European Studies 
PLoS ONE  2012;7(7):e35463.
Background
Tobacco smoking is a major contributor to the public health burden and healthcare costs worldwide, but the determinants of smoking behaviours are poorly understood. We conducted a large individual-participant meta-analysis to examine the extent to which work-related stress, operationalised as job strain, is associated with tobacco smoking in working adults.
Methodology and Principal Findings
We analysed cross-sectional data from 15 European studies comprising 166 130 participants. Longitudinal data from six studies were used. Job strain and smoking were self-reported. Smoking was harmonised into three categories never, ex- and current. We modelled the cross-sectional associations using logistic regression and the results pooled in random effects meta-analyses. Mixed effects logistic regression was used to examine longitudinal associations. Of the 166 130 participants, 17% reported job strain, 42% were never smokers, 33% ex-smokers and 25% current smokers. In the analyses of the cross-sectional data, current smokers had higher odds of job strain than never-smokers (age, sex and socioeconomic position-adjusted odds ratio: 1.11, 95% confidence interval: 1.03, 1.18). Current smokers with job strain smoked, on average, three cigarettes per week more than current smokers without job strain. In the analyses of longitudinal data (1 to 9 years of follow-up), there was no clear evidence for longitudinal associations between job strain and taking up or quitting smoking.
Conclusions
Our findings show that smokers are slightly more likely than non-smokers to report work-related stress. In addition, smokers who reported work stress smoked, on average, slightly more cigarettes than stress-free smokers.
doi:10.1371/journal.pone.0035463
PMCID: PMC3391192  PMID: 22792154
6.  Job Strain and Alcohol Intake: A Collaborative Meta-Analysis of Individual-Participant Data from 140 000 Men and Women 
PLoS ONE  2012;7(7):e40101.
Background
The relationship between work-related stress and alcohol intake is uncertain. In order to add to the thus far inconsistent evidence from relatively small studies, we conducted individual-participant meta-analyses of the association between work-related stress (operationalised as self-reported job strain) and alcohol intake.
Methodology and Principal Findings
We analysed cross-sectional data from 12 European studies (n = 142 140) and longitudinal data from four studies (n = 48 646). Job strain and alcohol intake were self-reported. Job strain was analysed as a binary variable (strain vs. no strain). Alcohol intake was harmonised into the following categories: none, moderate (women: 1–14, men: 1–21 drinks/week), intermediate (women: 15–20, men: 22–27 drinks/week) and heavy (women: >20, men: >27 drinks/week). Cross-sectional associations were modelled using logistic regression and the results pooled in random effects meta-analyses. Longitudinal associations were examined using mixed effects logistic and modified Poisson regression. Compared to moderate drinkers, non-drinkers and (random effects odds ratio (OR): 1.10, 95% CI: 1.05, 1.14) and heavy drinkers (OR: 1.12, 95% CI: 1.00, 1.26) had higher odds of job strain. Intermediate drinkers, on the other hand, had lower odds of job strain (OR: 0.92, 95% CI: 0.86, 0.99). We found no clear evidence for longitudinal associations between job strain and alcohol intake.
Conclusions
Our findings suggest that compared to moderate drinkers, non-drinkers and heavy drinkers are more likely and intermediate drinkers less likely to report work-related stress.
doi:10.1371/journal.pone.0040101
PMCID: PMC3391232  PMID: 22792218
7.  Stressful life events and the onset of asthma 
The European Respiratory Journal  2010;37(6):1360-1365.
The status of stressful life events as a risk factor for asthma is unclear and may be dependent on pre-existing allergic rhinitis. This study examined whether exposure to stressful life events predicted the onset of asthma in adults.
This is a prospective, population-based cohort study of 16,881 men and women, aged 20–54 and free of diagnosed asthma at the beginning of the follow-up (January 1, 2004). Data about stressful life events were gathered with a postal survey. The onset of asthma was ascertained through national registers until December 31, 2005.
During the follow-up period, 192 incident cases of asthma were identified. High total exposure to stressful life events, as indicated by a cumulative severity score, predicted the onset of asthma (HR 1.96; 95% CI 1.22–3.13). This association was robust to adjustment for demographics, smoking, and having a cat/dog at home, and it was observed both among those with and without allergic rhinitis at the baseline. Of the 10 most stressful life events, the illness of a family member, marital problems, divorce or separation, and conflicts with a supervisor were associated with the onset of asthma.
Our study suggests that stressful life events may increase the onset of asthma.
doi:10.1183/09031936.00164609
PMCID: PMC3319299  PMID: 21030455
asthma; asthma epidemiology; asthma onset; stressful life events
8.  Non-response in a nationwide follow-up postal survey in Finland: a register-based mortality analysis of respondents and non-respondents of the Health and Social Support (HeSSup) Study 
BMJ Open  2012;2(2):e000657.
Objective
To examine difference in mortality between postal survey non-respondents and respondents.
Design
A prospective cohort study with baseline survey in 1998 and comprehensive linkage to national mortality registers until 2005, the Health and Social Support study.
Setting
A population-based postal survey of the working-aged population in Finland in 1998.
Participants
The original random sample comprised 64 797 working-aged individuals in Finland (20–24, 30–34, 40–44, 50–54 years of age; 32 059 women and 32 716 men), yielding 25 898 (40.0%) responses in the baseline postal survey in 1998.
Primary outcome measure
Registry-based primary causes of death encoded with the International Classification of Diseases (ICD-10).
Results
In women, HR for total mortality was 1.75 (95% CI 1.40 to 2.19) times higher among the non-respondents compared with the respondents. In men, non-response was associated with a 1.41-fold (1.21–1.65) excess risk of total mortality. Non-response associated in certain age groups with deaths due to diseases in women and with deaths due to external causes in men. The most prominent excess mortality was seen for total mortality for both genders and for mortality due to external causes among men.
Conclusions
Postal surveys result in slight underestimation of illness prevalence.
Article summary
Article focus
Women and individuals from upper social strata tend to participate more actively in postal health surveys.
What this exactly means in terms of health selection among respondents is unclear.
Postal health surveys are believed to produce underestimates of illness prevalence.
Key messages
Total mortality was consistently and for women in the age group ≥50 years and for men in the age groups ≥40 years significantly higher among non-respondents compared with respondents during a 7-year follow-up among a total Finnish nationwide sample in working age comprising almost 65 000 individuals.
The excess mortality observed was 1.5–2 fold. Among men, it was explained by external causes, whereas among women, it was due to diseases and was statistically significant only in the age group 50–54 years.
Postal surveys result in slight underestimation of illness prevalence.
Strengths and limitations of the study
The linkage to mortality data was successful for virtually all individuals of the original sample comprising nearly 65 000 individuals. The sample size secures the reliability of the conclusions drawn. Furthermore, the registry data on mortality in Finland can be considered as reliable. To the best of the authors' knowledge, a corresponding study based on an as large a sample as in this study has not previously been carried out.
Some inaccuracy concerning the final diagnosis of death is possible. A further study limitation is that data of socioeconomic status or educational level of non-respondents were not available, and hence, adjustments of the statistical analyses for these variables were not possible.
doi:10.1136/bmjopen-2011-000657
PMCID: PMC3307122  PMID: 22422917
9.  Comparison of alternative versions of the job demand-control scales in 17 European cohort studies: the IPD-Work consortium 
BMC Public Health  2012;12:62.
Background
Job strain (i.e., high job demands combined with low job control) is a frequently used indicator of harmful work stress, but studies have often used partial versions of the complete multi-item job demands and control scales. Understanding whether the different instruments assess the same underlying concepts has crucial implications for the interpretation of findings across studies, harmonisation of multi-cohort data for pooled analyses, and design of future studies. As part of the 'IPD-Work' (Individual-participant-data meta-analysis in working populations) consortium, we compared different versions of the demands and control scales available in 17 European cohort studies.
Methods
Six of the 17 studies had information on the complete scales and 11 on partial scales. Here, we analyse individual level data from 70 751 participants of the studies which had complete scales (5 demand items, 6 job control items).
Results
We found high Pearson correlation coefficients between complete scales of job demands and control relative to scales with at least three items (r > 0.90) and for partial scales with two items only (r = 0.76-0.88). In comparison with scores from the complete scales, the agreement between job strain definitions was very good when only one item was missing in either the demands or the control scale (kappa > 0.80); good for job strain assessed with three demand items and all six control items (kappa > 0.68) and moderate to good when items were missing from both scales (kappa = 0.54-0.76). The sensitivity was > 0.80 when only one item was missing from either scale, decreasing when several items were missing in one or both job strain subscales.
Conclusions
Partial job demand and job control scales with at least half of the items of the complete scales, and job strain indices based on one complete and one partial scale, seemed to assess the same underlying concepts as the complete survey instruments.
doi:10.1186/1471-2458-12-62
PMCID: PMC3328260  PMID: 22264402
Job demands; Job control; Job strain; Work stress; Agreement
10.  Does depression predict coronary heart disease and cerebrovascular disease equally well? The Health and Social Support Prospective Cohort Study 
Background The relationship between depression and cerebrovascular disease (CBVD) continues to be debated although little research has compared the predictive power of depression for coronary heart disease (CHD) with that for CBVD within the same population. This study aimed to compare the importance of depression for CHD and CBVD within the same population of adults free of apparent cardiovascular disease.
Methods A random sample of 23 282 adults (9507 men, 13 775 women) aged 20–54 years were followed up for 7 years. Fatal and first non-fatal CHD and CBVD events were documented by linkage to the National-hospital-discharge and mortality registers.
Results Sex–age–education-adjusted hazard ratio (HR) for CHD was 1.66 [95% confidence interval (CI) 1.24–2.24] for participants with mild to severe depressive symptoms, i.e. those scoring ≥10 on the 21-item Beck Depression Inventory, and 2.04 (1.27–3.27) for those who filled antidepressant prescriptions compared with those without depression markers in 1998, i.e. at study baseline. For CBVD, the corresponding HRs were 1.01 (0.67–1.53) and 1.77 (0.95–3.29). After adjustment for behavioural and biological risk factors these associations were reduced but remained evident for CHD, the adjusted HRs being 1.47 (1.08–1.99) and 1.72 (1.06–2.77). For CBVD, the corresponding multivariable adjusted HRs were 0.87 (0.57–1.32) and 1.52 (0.81–2.84).
Conclusions Self-reported depression using a standardized questionnaire and clinical markers of mild to severe depression were associated with an increased risk for CHD. There was no clear evidence that depression is a risk factor for CBVD, but this needs further confirmation.
doi:10.1093/ije/dyq050
PMCID: PMC2950797  PMID: 20360321
Depression; coronary heart disease; cerebrovascular disease
11.  Does depression predict coronary heart disease and cerebrovascular disease equally well? The Health and Social Support Prospective Cohort Study 
Background
The relationship between depression and cerebrovascular disease (CBVD) continues to be debated although little research has compared the predictive power of depression for coronary heart disease (CHD) to that for CBVD within the same population. This study aimed to compare the importance of depression for CHD and CBVD within the same population of adults free of apparent cardiovascular disease.
Methods
A random sample of 23282 adults (9507 men, 13775 women) aged 20–54 years were followed-up for 7 years. Fatal and first non-fatal CHD and CBVD events were documented by linkage to the National-hospital-discharge and mortality registers.
Results
Sex-age-education-adjusted Hazard Ratio (HR) for CHD was 1.66 (95% confidence interval (CI) 1.24–2.24) for participants with mild to severe depressive symptoms, i.e. those scoring 10 or more on the 21-item Beck-Depression-Inventory, and 2.04 (1.27–3.27) for those who filled antidepressant prescriptions compared to those without depression markers in 1998, i.e., at study baseline. For CBVD, the corresponding HRs were 1.01 (0.67–1.53) and 1.77 (0.95–3.29). After adjustment for behavioural and biological risk factors these associations were reduced but remained evident for CHD, the adjusted HRs being 1.47 (1.08–1.99) and 1.72 (1.06–2.77). For CBVD, the corresponding multivariable adjusted HRs were 0.87 (0.57–1.32) and 1.52 (0.81–2.84).
Conclusions
Self-reported depression using a standardized questionnaire and clinical markers of mild to severe depression were associated with an increased risk for CHD. There was no clear evidence that depression is a risk factor for CBVD, but this needs further confirmation.
doi:10.1093/ije/dyq050
PMCID: PMC2950797  PMID: 20360321
Adult; Coronary Disease; epidemiology; psychology; Depression; complications; Female; Finland; epidemiology; Humans; Incidence; Male; Middle Aged; Proportional Hazards Models; Prospective Studies; Risk Factors; Stroke; epidemiology; psychology; Young Adult; depression; coronary heart disease; cerebrovascular disease
12.  Psychological and Somatic Symptoms of Anxiety and Risk of Coronary Heart Disease: The Health and Social Support Prospective Cohort Study 
Biological psychiatry  2009;67(4):378-385.
Background
Despite evidence showing anxiety to be a negative emotion that can be accompanied by various psychological and somatic complaints, previous studies have rarely considered these two components of anxiety separately in relation to coronary heart disease (CHD) events. This study aims to examine the extent to which the psychological and somatic components of anxiety are predictive of CHD.
Methods
This is a prospective population-based cohort study of 24,128 participants (9830 men, 14,298 women) aged 20 to 54 years. Psychological and somatic symptoms were assessed at study baseline in 1998. Fatal and nonfatal CHD events during the following 7 years were documented from data on hospitalizations from the National Hospital Discharge Register and mortality records from the Statistics Finland Register.
Results
In men, unadjusted hazard ratios for CHD per one unit increase in mean score were 1.50 (95% confidence interval [CI], 1.21–1.87) for somatic symptoms and 1.04 (95% CI, .85–1.29) for psychological symptoms. After serial adjustment for sociodemographic characteristics, biobehavioral risk factors, and clinically significant symptoms of depression, these associations were completely attenuated. In women, the corresponding unadjusted hazard ratios were 2.25 (95% CI, 1.66–3.06) and 1.55 (95% CI, 1.12–2.13), respectively. The corresponding fully adjusted hazard ratios were 1.47 (95% CI, 1.04–2.06) and 1.24 (95% CI, .91–1.70).
Conclusions
Somatic symptoms of anxiety were robustly associated with an increased risk of CHD in women. This finding lends support to the physiological pathway for the association between psychological factors, anxiety in particular, and CHD.
doi:10.1016/j.biopsych.2009.07.040
PMCID: PMC2963017  PMID: 19819425
Coronary heart disease; dimensions of anxiety; epidemiology
13.  Low pessimism protects against stroke: the Health and Social Support (HeSSup) prospective cohort study 
Background and Purpose
The association between optimism and pessimism and health outcomes has attracted increasing research interest. To date, the association between these psychological variables and risk of stroke remains unclear. We examined the relationship between pessimism and the 7-year incidence of stroke.
Methods
A random sample of 23 216 adults (9 480 men, 13 796 women) aged 20–54 years completed the pessimism scale in 1998, i.e., at study baseline. Fatal and first non-fatal stroke events during a mean follow-up of 7.0 years were documented by linkage to the National-hospital-discharge and mortality registers, leading to 105 events.
Results
Unadjusted hazard ratio was 0.44 (95% CI 0.25–0.77) for participants in the lowest quartile (a low pessimism level) when compared to those in the highest quartile (a high pessimism level). After serial adjustments for sociodemographic characteristics, cardiovascular biobehavioral risk factors, depression, general feeling of stressfulness, and ischemic-heart disease the fully-adjusted hazard ratio was 0.52 (95% CI 0.29–0.93).
Conclusions
In this population of adult men and women, low level of pessimism had a robust association with reduced incidence of stroke.
doi:10.1161/STROKEAHA.109.565440
PMCID: PMC2884028  PMID: 19892995
Adult; Attitude; Cohort Studies; Female; Follow-Up Studies; Health Status; Humans; Male; Middle Aged; Prospective Studies; Risk Factors; Social Support; Stroke; prevention & control; psychology; Young Adult
14.  Childhood adversities as a predictor of disability retirement 
Background
There is a large body of research on adulthood risk factors for retirement due to disability, but studies on the effect of adverse childhood experiences are scarce.
Aim
To examine whether adverse childhood experiences predict disability retirement.
Methods
Data were derived from the Health and Social Support Study. The information was gathered from postal surveys in 1998 (baseline) and in 2003 (follow‐up questionnaire). The analysed data consisted of 8817 non‐retired respondents aged 40–54 years (5149 women, 3668 men). Negative childhood experiences, such as financial difficulties, serious conflicts and alcohol‐related problems, were assessed at baseline and disability retirement at follow‐up.
Results
The risk of disability retirement increased in a dose–response manner with increasing number of childhood adversities. Respondents who had experienced multiple childhood adversities had a 3.46‐fold increased risk (95% CI 2.09 to 5.71) of disability retirement compared with those who reported no such adversities. Low socioeconomic status, depression (Beck Depression Inventory‐21), use of drugs for somatic diseases as well as health‐related risk behaviour, such as smoking, heavy alcohol consumption and obesity, were also predictors of disability retirement. After simultaneous adjustments for all these risk factors, the association between childhood adversities and the risk of disability retirement attenuated, but remained significant (OR 1.90, 95% CI 1.07 to 3.37).
Conclusions
Information on childhood conditions may increase our understanding of the determinants of early retirement, especially due to mental disorders. Childhood adversities should be taken into account when considering determinants of disability retirement and identifying groups at risk.
doi:10.1136/jech.2006.052670
PMCID: PMC2465717  PMID: 17496255
15.  Origins of Handedness: A nationwide study of 30161 adults 
Neuropsychologia  2009;47(5):1294-1301.
The origins of human handedness remain unknown. Genetic theories of handedness have received much attention, but some twin studies suggest modest, perhaps negligible genetic effects on handedness. A related question concerning handedness is whether twins have higher rates of left-handedness than do singletons. We studied handedness, with information on forced right-handedness, in a sample of 30,161 subjects aged 18–69 from a questionnaire survey of the older Finnish Twin Cohort. Left-handedness was found to be more common in twins (8.1%) and triplets (7.1%) than in singletons (5.8%), whereas ambidextrousness was more common in triplets (6.4%) than in twins (3.4%) and singletons (3.5%). As in many other studies, males were more likely to be left-handed. Ambidextrous subjects were more likely to become right-handed writers even if not forced to use their right hand. We fit maximum likelihood models to our twin data to estimate the contribution of additive genetic, common environment and unique environmental effects to hand preference. Results, depending on the model, indicate that unique environmental effects account for most observed variance in handedness, both in childhood (92–100%) and adulthood (74–86%). When forced right-handedness was taken into account, estimates of familial effects increased. Concordance for left-handedness in twins is rare, and accordingly, very large samples are needed to detect the familial effects. Our results show that forced-handedness can have an effect on estimates of genetic effects.
doi:10.1016/j.neuropsychologia.2009.01.007
PMCID: PMC2680751  PMID: 19428393
ambidextrousness; forced handedness; genetic effects; left-handedness; twins
16.  Characteristics and health consequences of intermittent smoking: Long-term follow-up among Finnish adult twins 
Nicotine & Tobacco Research  2009;11(2):148-155.
Introduction:
The definition of a smoker as someone who smokes daily has been challenged. No consensus exists regarding whether intermittent smoking represents transition toward daily smoking or cessation or whether intermittent smokers consistently maintain their low tobacco use frequency. Although abundant evidence supports the adverse health consequences of daily smoking, less evidence is available on intermittent smoking.
Methods:
We examined characteristics and health consequences of intermittent cigarette smoking among Finnish adult twins. We used longitudinal data of 21,340 persons with smoking status from questionnaires in 1975 and 1981 and data on lung cancer incidence from 1982 to 2004 from the Finnish Cancer Registry.
Results:
We identified 641 consistent intermittent smokers comprising 3% of the study population. Consistent intermittent smokers had higher education, less use of other tobacco products, healthier lifestyles, and partly more favorable mental health profiles compared with lifetime regular smokers. However, in terms of other lifestyle factors, intermittent smokers compared mostly unfavorably with never-smokers, despite being better educated. Intermittent smoking showed substantial heritability. There were 213 incident lung cancer cases among all study subjects; only one case was found among the intermittent smokers. The sex- and age-adjusted hazard ratios of lung cancer were not significantly elevated for the intermittent smokers, but they were increased more than 10-fold for all other smokers.
Discussion:
Although the present study did not find evidence of elevated lung cancer risk among intermittent smokers, compared with never-smokers, further studies should investigate other health consequences of intermittent smoking, such as cardiovascular and nonmalignant pulmonary outcomes.
doi:10.1093/ntr/ntn023
PMCID: PMC2658898  PMID: 19246432
17.  Hearing as a Predictor of Falls and Postural Balance in Older Female Twins 
Background
The purpose of the present study was to examine, first, whether hearing acuity predicts falls and whether the potential association is explained by postural balance and, second, to examine whether shared genetic or environmental effects underlie these associations.
Methods
Hearing was measured using a clinical audiometer as a part of the Finnish Twin Study on Aging in 103 monozygotic and 114 dizygotic female twin pairs aged 63–76 years. Postural balance was indicated as a center of pressure (COP) movement in semitandem stance, and participants filled in a fall-calendar daily for an average of 345 days after the baseline.
Results
Mean hearing acuity (better ear hearing threshold level at 0.5–4 kHz) was 21 dB (standard deviation [SD] 12). Means of the COP velocity moment for the best to the poorest hearing quartiles increased linearly from 40.7 mm2/s (SD 24.4) to 52.8 mm2/s (SD 32.0) (p value for the trend = .003). Altogether 199 participants reported 437 falls. Age-adjusted incidence rate ratios (IRRs) for falls, with the best hearing quartile as a reference, were 1.2 (95% confidence interval [CI] = 0.4–3.8) in the second, 4.1 (95% CI = 1.1–15.6) in the third, and 3.4 (95% CI = 1.0–11.4) in the poorest hearing quartiles. Adjustment for COP velocity moment decreased IRRs markedly. Twin analyses showed that the association between hearing acuity and postural balance was not explained by genetic factors in common for these traits.
Conclusion
People with poor hearing acuity have a higher risk for falls, which is partially explained by their poorer postural control. Auditory information about environment may be important for safe mobility.
doi:10.1093/gerona/gln015
PMCID: PMC2655032  PMID: 19182227
Hearing; Postural balance; Fall; Twin study; Heritability; Aging
18.  Sense of coherence and intentions to retire early among Finnish women and men 
BMC Public Health  2010;10:22.
Background
Previous studies have shown that age, physical and mental health status and working circumstances, along with different socio-economic and psychosocial factors affect the retirement process. However, the role of psychological resources, such as sense of coherence (SOC), on the retirement process is still poorly understood. This study investigated the associations between SOC and intentions to retire early and whether these associations were explained by socio-economic, psychosocial and work and health related factors.
Methods
The data were derived from the Finnish Health and Social Support (HeSSup) Study. The information was gathered from postal surveys in 1998 (baseline) and in 2003 (follow-up). The analyzed data consisted of 7409 women and 4866 men aged 30-54 at baseline. SOC and background factors including childhood circumstances, language, education, working circumstances, social support, health behaviour and somatic and mental health status were assessed at baseline. The intentions to retire early were assessed at follow-up using logistic regression analysis.
Results
SOC was associated with intentions to retire early among both genders. Socio-economic, psychosocial and work and health behaviour related factors did not influence the association between SOC and intentions to retire early among women and men reporting somatic or mental illness. Further, the association between SOC and intentions to retire early remained among (somatically and mentally) healthy men. Among healthy women the association was weaker and statistically non-significant. Among unhealthy women, the odds ratios of SOC was 0.97 (CI 95% 0.96-0.98) and 0.97 among ill men (CI 95% 0.96-0.98), i.e., each additional SOC score reduced the risk of intentions by 3% among both genders.
Conclusion
Unhealthy employees with low SOC and low education were in the greatest risk to have reported intentions to retire early. SOC had an independent effect on intentions to retire early, and a strong SOC may have a potential to prevent early retirement in groups otherwise at risk. An important challenge would be to target the resources of SOC to the most vulnerable and design appropriate interventions in order to strengthen the level of SOC and hence prolong working years of the aging employees.
doi:10.1186/1471-2458-10-22
PMCID: PMC2831030  PMID: 20085637
19.  Peptic ulcer and childhood adversities experienced by working-aged people 
AIM: To study the association between self-reported peptic ulcer and childhood adversities.
METHODS: The Health and Social Support Study (HeSSup) population consisted of a stratified random sample drawn from the Finnish Population Register in four age groups: 20-24, 30-34, 40-44 and 50-54. The survey was carried out by postal questionnaire during 1998, with a response rate of 40.0%. A follow-up questionnaire was sent during 2003 to all those who responded to the first. Altogether 19 626 individuals returned the follow-up questionnaire; a response rate of 75.8%. The subjects were asked whether a doctor had told them that they have or have had peptic ulcer. The analyses covered those who responded affirmatively to both the baseline and the follow-up enquiries (n = 718). Those not reporting a peptic ulcer in either of the two questionnaires (n = 17 677) were taken as controls. The subjects were further requested (through six questions) to think about their childhood adversities.
RESULTS: The most common adversities mentioned were long-lasting financial difficulties in the family, serious conflicts in the family, and a family member seriously or chronically ill. All the adversities reported, except parental divorce, were more common among peptic ulcer patients than among controls (P values varied between < 0.001 and 0.003). Age- and sex-adjusted odds ratios (OR) of childhood adversities in the multivariate logistic analysis for self-reported peptic ulcer varied between 1.45 and 2.01. Adjusting for smoking, heavy drinking, stress and nonsteroidal anti-inflammatory drug use had no further influence (ORs between 1.22 and 1.73).
CONCLUSION: Our findings suggest that childhood adversities maintain a connection with and have a predictive role in the development of peptic ulcer.
doi:10.3748/wjg.15.3405
PMCID: PMC2712902  PMID: 19610142
Peptic ulcer; Working-aged; Childhood adversities; Stress factors; Predictive role
20.  Verbal recall and recognition in twins discordant for schizophrenia 
Psychiatry research  2008;159(3):271-280.
The nature, neural underpinnings, and etiology of deficits in verbal declarative memory in patients with schizophrenia remain unclear. To examine the contributions of genes and environment to verbal recall and recognition performance in this disorder, the California Verbal Learning Test was administered to a large population-based Finnish twin sample, which included schizophrenic and schizoaffective patients, their non-ill monozygotic (MZ) and dizygotic (DZ) co-twins, and healthy control twins. Compared with controls, patients and their co-twins showed relatively greater performance deficits on free recall compared with recognition. Intra-pair differences between patients and their non-ill co-twins in hippocampal volume and memory performance were highly positively correlated. These findings are consistent with the view that genetic influences are associated with reduced verbal recall in schizophrenia, but that non-genetic influences further compromise these abnormalities in patients who manifest the full-blown schizophrenia phenotype, with this additional degree of disease-related declarative memory deficit mediated in part by hippocampal pathology.
doi:10.1016/j.psychres.2007.03.003
PMCID: PMC2519867  PMID: 18442861
CVLT; Twin; Neuropsychology; Memory; Genes; Environment; Hippocampus
21.  The Genetic Liability to Disability Retirement: A 30-Year Follow-Up Study of 24,000 Finnish Twins 
PLoS ONE  2008;3(10):e3402.
Background
No previous studies on the effect of genetic factors on the liability to disability retirement have been carried out. The main aim of this study was to investigate the contribution of genetic factors on disability retirement due to the most common medical causes, including depressive disorders.
Methods
The study sample consisted of 24 043 participants (49.7% women) consisting of 11 186 complete same-sex twin pairs including 3519 monozygotic (MZ) and 7667dizygotic (DZ) pairs. Information on retirement events during 1.1.1975–31.12.2004, including disability pensions (DPs) with diagnoses, was obtained from the Finnish nationwide official pension registers. Correlations in liability for MZ and DZ twins and discrete time correlated frailty model were used to investigate the genetic liability to age at disability retirement.
Results
The 30 year cumulative incidence of disability retirement was 20%. Under the best fitting genetic models, the heritability estimate for DPs due to any medical cause was 0.36 (95% CI 0.32–0.40), due to musculoskeletal disorders 0.37 (0.30–0.43), cardiovascular diseases 0.48 (0.39–0.57), mental disorders 0.42 (0.35–0.49) and all other reasons 0.24 (0.17–0.31). The effect of genetic factors decreased with increasing age of retirement. For DP due to depressive disorders, 28% of the variance was explained by environmental factors shared by family members (95% CI 21–36) and 58% of the variance by the age interval specific environmental factors (95% CI 44–71).
Conclusions
A moderate genetic contribution to the variation of disability retirement due to any medical cause was found. The genetic effects appeared to be stronger at younger ages of disability retirement suggesting the increasing influence of environmental factors not shared with family members with increasing age. Familial aggregation in DPs due to depressive disorders was best explained by the common environmental factors and genetic factors were not needed to account for the pattern of familial aggregation.
doi:10.1371/journal.pone.0003402
PMCID: PMC2566596  PMID: 18923678
22.  Catechol-O-Methyltransferase Gene Polymorphism Is Associated with Skeletal Muscle Properties in Older Women Alone and Together with Physical Activity 
PLoS ONE  2008;3(3):e1819.
Background
Muscle strength declines on average by one percent annually from midlife on. In postmenopausal women this decrement coincides with a rapid decline in estrogen production. The genetics underlying the effects of estrogen on skeletal muscle remains unclear. In the present study, we examined whether polymorphisms within COMT and ESR1 are associated with muscle properties and assessed their interaction and their combined effects with physical activity.
Methodology/Principal Findings
A cross-sectional data analysis was conducted with 434 63-76-year-old women from the population-based Finnish Twin Study on Aging. Body anthropometry, muscle cross-sectional area (mCSA), isometric hand grip and knee extension strengths, and leg extension power were measured. COMT Val158Met and ESR1 PvuII genotypes were determined by the RFLP method. mCSA differed by COMT genotypes (p = 0.014) being significantly larger in LL than HL individuals in unadjusted (p = 0.001) and age- and height-adjusted model (p = 0.004). When physical activity and age were entered into GEE model, COMT genotype had a significant main effect (p = 0.038) on mCSA. Furthermore, sedentary individuals with the HH genotype had lower muscle mass, strength and power, but they also appeared to benefit the most from physical activity. No association of ESR1 PvuII polymorphism with any of the muscle outcomes was observed.
Conclusions/Significance
The present study suggests that the COMT polymorphism, affecting the activity of the enzyme, is associated with muscle mass. Furthermore, sedentary individuals with potential high enzyme activity were the weakest group, but they may potentially benefit the most from physical activity. This observation elucidates the importance of both environmental and genetic factors in muscle properties.
doi:10.1371/journal.pone.0001819
PMCID: PMC2265555  PMID: 18350156
23.  Employment status and differences in the one-year coverage of physician visits: different needs or unequal access to services? 
Background
The dichotomy employed vs. unemployed is still a relevant, but rather crude measure of status in current labour markets. Also, studies concerning the association of employment status with health have to specify the type of the employment as well as the characteristics of the unemployment. This study aims to reveal differences and potential inequalities in physician visits among seven groups in the core-periphery structures of the labour markets.
Methods
A total of 16 000 Finns responded to a postal survey in 2003. Their visits to physicians in public primary health care, occupational health care, private health services, hospital outpatient clinics and dental care services during previous year were measured as indicators of service utilisation. Participants were classified as employees having a permanent or fixed-term and full-time or part-time contract and as those experiencing short-term, prolonged or long-term unemployment. Differences in the one-year coverage of physician visits between these groups of employees were analysed using logistic regression analyses where differences in the need for services were controlled for by including demographics and self-rated health assessments in the models.
Results
Permanently employed respondents had visited a physician most often, and the need-adjusted regression models showed significantly lower odds ratios for a visit among fixed-term employees (OR 0.65, 95% CI 0.53–0.81) and in particular among the long-term unemployed (OR 0.21, 95% CI 0.14–0.31). A stratified analysis according to health care sector showed the lowest odds ratios in occupational health care and private physicians (ORs between 0.05 and 0.73) and also low odds ratios for dentists (ORs between 0.45 and 0.91), whereas visits to public primary health care were more common among non-permanent employees and the unemployed (ORs between 1.46 and 2.39).
Conclusion
The use of physician services varies according to labour market status, being relatively low among the non-permanently employed and the unemployed. This underuse is emphasised when clinical need is taken into account. The main reasons for the variance evidently lie in the structures of the Finnish health service system. The result may indicate non-optimal health care of the population on the periphery of the labour market, but it may also reflect the importance of employment status as a context for need and the decision to visit a physician.
doi:10.1186/1472-6963-6-123
PMCID: PMC1618837  PMID: 17014702
24.  Gene expression profiles in Finnish twins with multiple sclerosis 
BMC Medical Genetics  2006;7:11.
Background
Since genetic alterations influencing susceptibility to multiple sclerosis (MS), the most common autoimmune demyelinating disease of the central nervous system (CNS), are as yet poorly understood, the purpose of this study was to identify genes responsible for MS by studying monozygotic (MZ) twin pairs discordant for MS.
Methods
In order to identify genes involved in MS development, the gene expression profiles in blood mononuclear cells obtained from eight MZ twin pairs discordant for MS were analyzed by cDNA microarray technology detecting the expression of 8 300 genes. The twins were collected from the Finnish Twin Cohort Study and both affected subjects and their healthy siblings underwent neurological evaluation and cerebral and spinal magnetic resonance imaging. Gene expressions were confirmed by relative quantitative reverse transcription PCR.
Results
It appeared that 25 genes were at least two-fold up-regulated and 15 genes down-regulated in 25% (2/8) of twins with MS when compared to their healthy siblings. Moreover, 6/25 genes were up-regulated in 40% of MS twins and one gene, interferon alpha-inducible protein (clone IFI-6-16) (G1P3), in 50% of them. The six most constantly expressed genes are (1) G1P3, (2) POU domain, class 3, transcription factor 1, (3) myxovirus resistance 2, (4) lysosomal-associated multispanning membrane protein-5, (5) hemoglobin alpha 2 and (6) hemoglobin beta.
Conclusion
Over two-fold up-regulation of these six genes in almost half of MZ twins with MS suggests their role in MS pathogenesis. Studies using MZ MS twins obtained from genetically homogeneous population offer a unique opportunity to explore the genetic nature of MS.
doi:10.1186/1471-2350-7-11
PMCID: PMC1421383  PMID: 16504146
25.  The stability of life satisfaction in a 15-year follow-up of adult Finns healthy at baseline 
BMC Psychiatry  2005;5:4.
Background
While physical health has improved considerably over recent decades in Finland, the disease burden of mental health, especially that of depression, has become increasingly demanding. However, we lack long-term data on the natural course of subjective well-being in the general population. The aim of this study was to investigate the long-term course of self-reported life satisfaction.
Methods
This was a 15-year prospective cohort study on a nationwide sample of adult Finnish twins (N = 9679), aged 18–45 and healthy at baseline, who responded to postal questionnaires in 1975, 1981 and 1990 including a 4-item life satisfaction scale (happiness/easiness/interest in life and feelings of loneliness). Life satisfaction score (range: 4–20) was classified into three categories: satisfied (4–6), intermediate (7–11) and dissatisfied group (12–20). The associations between life satisfaction scores during the follow-up were studied with linear/logistic regression.
Results
Moderate stability and only a slight effect of age or birth-cohort on mean life satisfaction score (LS) were detected. In 1990, 56% of all and 31% of the dissatisfied remained in the same LS category as at baseline. Only 5.9% of the study subjects changed from being satisfied to dissatisfied or vice versa. Correlations between continuous scores (1975, 1981 and 1990) were 0.3–0.4. Baseline dissatisfaction (compared to satisfaction) predicted dissatisfaction in 1981 (OR = 10.4; 95%CI 8.3–13.1) and 1990 (5.6; 4.6–6.8). Multiple adjustments decreased the risk only slightly.
Conclusions
Life satisfaction in adult Finns was moderately stable during 15 years. Among an identifiable group (i.e. the dissatisfied) life dissatisfaction may become persistent, which places them at a greater risk of adverse health outcomes.
doi:10.1186/1471-244X-5-4
PMCID: PMC546219  PMID: 15656900

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