Diagnoses of common mental disorders among social workers in Sweden: A register-based cohort study

BACKGROUND

Little is known about common mental disorders (CMD) diagnoses among social workers, i.e., depression, anxiety, or stress-related disorders. This study aims to examine the risk of CMD among social workers in comparison to other workers and to further investigate differences between men and women and specific occupational titles.

METHODS

This register-based cohort study consists of 3,034,304 persons, of which 26,610 were social workers (0.9 % of all workers), aged 30-64 years, living in Sweden in 2015. The risk of diagnosed CMDs was followed up until 2020. Cox regression models were used to calculate hazard ratios (HR) and 95 % confidence intervals (CI), adjusting for sex, birth country, education, and birth year.

RESULTS

The participants were followed up by a total of 16,833,742.9 person-years, with an average follow-up of 5.5 years. Social workers, compared to other workers, were at a higher risk of CMD (HR 1.3, 95 % CI 1.2-1.4) after adjustment. The HR was equal, 1.3, for depression (95 % CI 1.2-1.5) and anxiety or stress-related disorder (95 % CI 1.2-1.4). The association between social work and CMD was stronger among men (HR 1.7, 95 % CI 1.6-1.9) compared to women (HR 1.2, 95 % CI 1.1-1.3). Further, men working as assistance analysts had the highest risk among the occupational categories (HR 2.2, 95 % CI 1.2-3.9).

LIMITATIONS

CMD diagnoses only included cases treated in secondary care.

CONCLUSIONS

Social workers, especially male social workers, had a higher risk of CMD. This deserves attention for future research and interventions aimed at improving the mental health of social workers.

The role of working conditions in educational differences in all-cause and ischemic heart disease mortality among Swedish men

OBJECTIVES

This study aims to investigate the extent to which low job control and heavy physical workload in middle age explain educational differences in all-cause and ischemic heart disease (IHD) mortality while accounting for important confounding factors.

METHODS

The study is based on a register-linked cohort of men who were conscripted into the Swedish military at around the age of 18 in 1969/1970 and were alive and registered in Sweden in 2005 (N=46 565). Cox proportional hazards regression models were built to estimate educational differences in all-cause and IHD mortality and the extent to which this was explained by physical workload and job control around age 55 by calculating the reduction in hazard ratio (HR) after adjustments. Indicators of health, health behavior, and other factors measured during conscription were accounted for.

RESULTS

We found a clear educational gradient for all-cause and IHD mortality (HR 2.07 and 2.47, respectively, for the lowest compared to the highest education level). A substantial part was explained by the differential distribution of the confounding factors. However, work-related factors, especially high physical workload, also played important explanatory roles.

CONCLUSION

Even after accounting for earlier life factors, low job control and especially high physical workload seem to be important mechanistic factors in explaining educational inequalities in all-cause and IHD mortality. It is therefore important to find ways to reduce physical workload and increase job control in order to decrease inequalities in mortality.

The impact of cardiorespiratory fitness and physical workload on disability pension-a cohort study of Swedish men

OBJECTIVE

Understanding the impact of physical capacity in combination with high physical workload could be beneficial for the prevention of health-related exits from work. Therefore, the aim of this study was to investigate the separate and combined effects of low cardiorespiratory fitness and high physical workload on disability pension (DP) due to any cause, musculoskeletal disorders (MSD), and cardiovascular diseases (CVD).

METHODS

A total of 279 353 men born between 1951 and 1961 were followed regarding DP between 2006 and 2020, ages 45-64. Cardiorespiratory fitness was assessed during military conscription, using an ergometer bicycle test. Physical workload was based on a job-exposure matrix (JEM) linked to occupational title in 2005. Cox regression models estimated separate and combined associations with DP.

RESULTS

Low cardiorespiratory fitness and high physical workload were associated with increased risk of DP. For all cause DP, the fully adjusted hazard ratio and 95% confidence interval for those with low cardiorespiratory fitness was 1.38 (1.32-1.46) and for those with high physical workload 1.48 (1.39-1.57). For all cause and MSD DP, but not for CVD DP, the combination of low cardiorespiratory fitness and high physical workload resulted in higher risks than when adding the effect of the single exposures.

CONCLUSION

Both low cardiorespiratory fitness in youth and later exposure to high physical workload were associated with an increased risk of DP, where workers with the combination of both low cardiorespiratory fitness and a high physical workload had the highest risks (all-cause and MSD DP).

The meaning of decision latitude in registered nurses' night work

PURPOSE

For many employees today, the work situation and work content differ from those of the industrial workers that were originally in mind when the well-known demand-control-support model was developed. The aim of this study was to gain a deeper understanding of the meaning of control, i.e., decision latitude, in post-industrial society, using night-working registered nurses as an example.

METHODS

As an example of a modern human service occupation in a value-based organization we choose registered nurses. Twenty-nine registered nurses from 11 departments at three different hospitals participated in semi-structured interviews. The analysis used a thematic approach and was deductive, based on an operationalization of decision latitude.

RESULTS

Findings indicate that the specific meaning of decision latitude is influenced by the specific work organization. Moreover, decision latitude appears to interact in a complex way with demands and support at work.

CONCLUSIONS

Decision latitude appears to be influenced by the specific work organization. Thus, when we address self-reported decision latitude, it can have different meanings and potentially different effects in different contexts. Moreover, the interface and interplay between the three constructs decision latitude, demand and support seems to be relevant and complex.

Trajectories of psychosocial working conditions and all-cause and cause-specific mortality: a Swedish register-based cohort study

OBJECTIVES

While psychosocial working conditions have been associated with morbidity, their associations with mortality, especially cause-specific mortality, have been less studied. Additionally, few studies considered the time-varying aspect of exposures. We aimed to examine trajectories of job demand-control status in relation to all-cause and cause-specific mortality, including cardiovascular diseases (CVD), suicide, and alcohol-related mortality.

METHODS

The study population consisted of around 4.5 million individuals aged 16-60 years in Sweden in 2005. Job control and demands were respectively measured using job exposure matrices (JEM). Trajectories of job control and demands throughout 2005-2009 were identified using group-based trajectory modelling, and job demand-control categories were subsequently classified. Deaths in 2010-2019 were recorded in the national cause of death register. Cox regression models were used.

RESULTS

A total of 116 242 individuals died in 2010-2019. For both job control and demands, we identified four trajectories, which were parallel to each other and represented four levels of exposures. Low control and passive jobs were associated with higher all-cause, CVD, and suicide mortality among both men and women. High strain jobs were associated with higher all-cause and CVD mortality among men, while low control, passive jobs, and high strain jobs were associated with higher alcohol-related mortality among women.

CONCLUSIONS

The trajectories identified may suggest stable levels of job control and demands over time. Poor psychosocial working conditions are related to all-cause and cause-specific mortality, and these patterns vary to some extent between men and women.

Job demands and job control and their associations with disability pension-a register-based cohort study of middle-aged and older Swedish workers

OBJECTIVES

Job demands and control at work and their combination, job strain, have been studied in relation to risk of disability pension (DP) previously. In the present study, based on registry data, we aimed to deepen the knowledge by analyzing major disease groups among the DPs, dose-response shape of the associations, and potential confounding effects of physical workload.

METHODS

Approximately 1.8 million workers aged 44 or older and living in Sweden in 2005 were followed up for 16 years, up to a maximum of 65 years of age. We linked mean values of job demands and job control, estimated in a job-exposure matrice (JEM) by gender, to individuals through their occupational titles in 2005. These values were categorized by rank order, and, for the construction of job-strain quadrants, we used a median cut-off. Associations with DP were estimated in Cox proportional-hazards models.

RESULTS

In models accounting for covariates including physical workload, low levels of job control were associated with higher risk of DP among both men and women. This association was most clear for DP with a psychiatric diagnosis, although a dose-response shape was found only among the men. High levels of job demands were associated with decreased risk of DP across diagnoses among men, but the same association varied from weak to non-existing among women. The high- and passive job-strain quadrants both showed increased risk of DP with a psychiatric diagnosis.

CONCLUSION

The results suggest that, at the occupational level, low job control, but not high job demands, contributes to an increased incidence of DP, particularly regarding DP with a psychiatric diagnosis.

Combined exposure to heavy physical workload and low job control and the risk of disability pension: A cohort study of employed men and women in Sweden

OBJECTIVE

To investigate the separate and combined effects of overall heavy physical workload (PWL) and low decision authority on all-cause disability pension (DP) or musculoskeletal DP.

METHODS

This study uses a sample of 1,804,242 Swedish workers aged 44-63 at the 2009 baseline. Job Exposure Matrices (JEMs) estimated exposure to PWL and decision authority. Mean JEM values were linked to occupational codes, then split into tertiles and combined. DP cases were taken from register data from 2010 to 2019. Cox regression models estimated sex-specific Hazard Ratios (HR) with 95% confidence intervals (95% CI). The Synergy Index (SI) estimated interaction effects.

RESULTS

Heavy physical workload and low decision authority were associated with an increased risk of DP. Workers with combined exposure to heavy PWL and low decision authority often had greater risks of all-cause DP or musculoskeletal DP than when adding the effects of the single exposures. The results for the SI were above 1 for all-cause DP (men: SI 1.35 95%CI 1.18-1.55, women: SI 1.19 95%CI 1.05-1.35) and musculoskeletal disorder DP (men: SI 1.35 95%CI 1.08-1.69, women: 1.13 95%CI 0.85-1.49). After adjustment, the estimates for SI remained above 1 but were not statistically significant.

CONCLUSION

Heavy physical workload and low decision authority were separately associated with DP. The combination of heavy PWL and low decision authority was often associated with higher risks of DP than would be expected from adding the effects of the single exposures. Increasing decision authority among workers with heavy PWL could help reduce the risk of DP.

Utilizing a Nordic Crosswalk for Occupational Coding in an Analysis on Occupation-Specific Prolonged Sickness Absence among 7 Million Employees in Denmark, Finland, Norway and Sweden

We identified occupations with a high incidence of prolonged sickness absence (SA) in Nordic employees and explored similarities and differences between the countries. Utilizing data from national registers on 25-59-year-old wage-earners from Denmark, Finland, Norway and Sweden, we estimated the gender- and occupation-specific age-adjusted cumulative incidence of SA due to any cause, musculoskeletal diseases and mental disorders. To increase the comparability of occupations between the countries, we developed a Nordic crosswalk for occupational codes. We ranked occupational groups with the incidence of SA being statistically significantly higher than the population average of the country in question and calculated excess fractions with the employee population being the reference group. We observed considerable occupational differences in SA within and between the countries. Few occupational groups had a high incidence in all countries, particularly for mental disorders among men. In each country, manual occupations typically had a high incidence of SA due to any cause and musculoskeletal diseases, while service occupations had a high incidence due to mental disorders. Preventive measures targeted at specific occupational groups have a high potential to reduce work disability, especially due to musculoskeletal diseases. Particularly groups with excess SA in all Nordic countries could be at focus.

Does a change to an occupation with a lower physical workload reduce the risk of disability pension? A cohort study of employed men and women in Sweden

OBJECTIVE

This study aimed to examine if a change to an occupation with a lower physical workload reduces the risk of all-cause disability pension (DP) and musculoskeletal DP (MDP).

METHODS

This study used a sample of 359 453 workers who were registered as living in Sweden in 2005 and aged 44-63 in 2010. Exposure to physical workload was measured from 2005-2010 by linking a mean value from a job exposure matrix to occupational codes. The mean values were then split into quartiles. All included participants had high exposure to physical workload (top quartile) from 2005-2007. A change in physical workload was measured as a change to (i) any lower quartile or (ii) medium-high or low quartiles from 2008-2010. DP cases were taken from register data from 2011-2016. Crude and multivariate Cox proportional-hazards regression models estimated sex-specific hazard ratios (HR) with 95% confidence intervals (CI).

RESULTS

Compared to workers with consistently high physical workload, a change to any lower quartile of physical workload was associated with a decreased risk of all-cause DP (men: HR 0.59, 95% CI 0.46-0.77, women: HR 0.63, 95% CI 0.52-0.76) and MDP (men: HR 0.52, 95% CI 0.31-0.89, women: HR 0.61, 95% CI 0.44-0.84). Older workers had the largest decreased risk for MDP. Generally, changing from high to low physical workload was associated with a greater reduced risk of DP than changing from high to medium-high physical workload.

CONCLUSIONS

Changing to an occupation with lower exposure to physical workload was associated with reduced risks of DP and MDP among both sexes.

Job control, job demands and job strain and suicidal behaviour among three million workers in Sweden

OBJECTIVE

To investigate the association between job control, job demands and their combination (job strain) and suicide attempts and deaths among male and female workers in Sweden.

METHODS

Job control and demands were measured separately for men and women using a job exposure matrix, which was linked to around three million individuals based on their occupational title in 2005. Suicide attempts and deaths were measured in the hospital and cause of death registers from 2006 to 2016. HRs were estimated using discrete proportional hazards models with annually updated age as the time axis. Models were adjusted for sociodemographic, family, health, labour market and childhood factors, as well as the time-varying effects of unemployment, sick leave and family factors during follow-up.

RESULTS

Low job control was associated with an increased risk of suicide attempts and deaths among both men and women while high job demands tended to be associated with a decreased risk. The combination of job control and job demands (job strain) reflected the increased risk of low control jobs and the decreased risk of high demand jobs. Associations were attenuated but still present after adjustments.

CONCLUSIONS

Low job control is related to suicide attempts and deaths, and this is only partially explained by important covariates measured both prebaseline and during follow-up. Attempts to increase job control among workers may be beneficial in preventing suicide.

Educational qualification differences and early labor market exit among men: the contribution of labor market marginalization measured across the working life

BACKGROUND

The present study aims to investigate the association between educational qualification and early labor market exit among men and to examine the contribution of labor market marginalization measured across the working life on this association.

METHOD

A register-linked cohort study was conducted including men who completed military service in 1969/70 (born between 1949 and 1951) and were alive at age 55 and not disability pension beneficiaries (n = 40 761). Information on the highest level of educational qualification and the outcome of early exit (disability pension, sickness absence, unemployment, and early old-age pension) was obtained from Swedish nationwide registers between the ages of 55 and 64 years. Labor market marginalization was defined as periods of long-term unemployment and sickness absence over the working life and up to follow-up. Cox regression analyses were used to obtain hazard ratios (HR) with 95% confidence intervals (CI).

RESULTS

Low-educated men were more likely to leave the labor force early due to disability pension or sickness absence (HR: 2.48), unemployment (HR: 2.09), and early old-age pension with- (HR:1.25) and without -income (HR: 1.58). Labor market marginalization across the working life explained a large part of the association for the more involuntary early exit routes (disability pensions, sickness absence, unemployment) and explained very little with regards to the more voluntary early exit routes (early old-age pension with and without income).

CONCLUSION

Exposure to labor market marginalization across the working life was important in explaining educational differences in early labor market exit due to disability pension or sickness absence and unemployment. This study underscores the importance of identifying and implementing preventive measures in the workplace (e.g. adaptions) to prevent new spells of sickness absence and unemployment, especially among low educated individuals.

Long-term sick leave for back pain, exposure to physical workload and psychosocial factors at work, and risk of disability and early-age retirement among aged Swedish workers

Purpose

To assess the risk of disability and early-age retirement associated with previous long-term sickness absence for back pain (back-pain SA), exposure to high physical workload, low job control, high demands and high strain, and to evaluate effect modification by work factors on the relationship between back-pain SA and premature retirement.

Methods

All employed Swedish residents born 1946–1955 (n = 835,956) were followed up from 2010 to 2016 for disability (DP) and early-age pension (EAP). Associations of premature retirement with exposure to work factors and back-pain SA in the 3 years before follow-up were estimated through proportional hazards models. Retirement, back-pain SA and covariates were assessed through administrative sources, and exposure to work factors through a job-exposure matrix.

Results

In both genders, back-pain SA was associated with DP (> 1 episode: HR 3.23 among men; HR 3.12 among women) and EAP (> 1 episode: HR 1.24 among men; HR 1.18 among women). Higher physical workload and lower job control were also associated with an increased DP risk in both genders, whereas higher job demands showed a decreased risk. For EAP, associations with work factors were weak and inconsistent across genders. No effect modification by work factors was found, except for a negative effect modification by job strain on DP risk among women, i.e. a reduced effect of back-pain SA with increasing exposure.

Conclusion

Back-pain SA was a significant predictor of both DP and EAP, while work factors were consistently associated only with DP. Our results indicate that the joint effect of back-pain SA and work factors on DP is additive and does not support effect modification by work factors.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00420-022-01862-8.

Psychosocial workplace factors and alcohol-related morbidity: a prospective study of 3 million Swedish workers

Background

Psychosocial workplace factors may be associated with alcohol-related morbidity, but previous studies have had limited opportunities to take non-occupational explanatory factors into account. The aim of this study is to investigate associations between job control, job demands and their combination (job strain) and diagnosed alcohol-related morbidity while accounting for several potentially confounding factors measured across the life-course, including education.

Methods

Job control, job demands and job strain were measured using the Swedish job exposure matrix measuring psychosocial workload on the occupational level linked to over 3 million individuals based on their occupational titles in 2005 and followed up until 2016. Cox regression models were built to estimate associations with alcohol-related diagnoses recorded in patient registers.

Results

Low job control was associated with an increased risk of alcohol-related morbidity, while high job demands tended to be associated with a decreased risk. Passive and high-strain jobs among men and passive jobs among women were also associated with an increased risk of alcohol diagnoses. However, all associations were found to be weakened in models adjusted for other factors measured prospectively over the life-course, especially in models that included level of education.

Conclusion

The associations between low job control and high job demands, and the risk of alcohol-related morbidity reflect underlying socioeconomic differences to some extent. Lower job control, however, remained associated with a higher risk of alcohol-related morbidity.

Depression among teachers: a Swedish register-based study

Background

Some studies have suggested that teachers are particularly at risk for mental health problems but the research in this area has not been conclusive. This study aims to compare the risk of being diagnosed with depression for different types of teachers in Sweden, both with each other and with the rest of the population, using register data.

Methods

Just over 3 million individuals age 30-60 were included of which 256,166 were teachers. The exposure variable was the occupation held in 2005 and the outcome was any diagnosis of depression during the follow up period of 2006 to 2016. The data was analyzed using Cox proportional hazard regression.

Results

Around 5 % of women and 3 % of men developed depression during the follow up. For women, teachers had a decreased risk of developing depression compared to non-teachers, but this association was no longer present after adjusting for common covariates including education. For men, teachers had an increased risk of depression both before and after adjustment (HR 1.27 95% CI 1.22-1.32). When comparing different kinds of teachers to university teachers, several types of teachers including primary and special education teachers had an increased risk among men while primary and secondary teachers had a decreased risk among women.

Conclusion

The increased risk of depression in male teachers is a result that requires further exploration in terms of occupational differences between male and female teachers.

Personality trait by intelligence interaction effects on grades tend to be synergistic

BACKGROUND

Earlier research has identified both synergistic and compensatory personality traits by intelligence interaction effects on academic performance.

METHODS

The present study employed data on intelligence, personality traits, and academic performance in the 1997 National Longitudinal Survey of Youth (NLSY97, N = 8984).

RESULTS

Some intelligence by personality trait interaction effects, mainly involving indicators of dependability, on high school grades were identified. The interaction effects tended to be synergistic, meaning that the association between the trait and grades tended to strengthen with increased intelligence. A positive association between intelligence and the reliability in the measurement of a dependability composite score accounted for a substantial portion of the synergistic dependability by intelligence interaction effect on academic performance.

CONCLUSIONS

Personality trait by intelligence interaction effects on academic performance tend to be synergistic and may, at least to some degree, be due to a positive association between intelligence and reliability in the measurement of personality traits.

Disability pensions related to heavy physical workload: a cohort study of middle-aged and older workers in Sweden

OBJECTIVES

The aim of the study was to examine the associations between heavy physical workload among middle-aged and older workers and disability pension due to any diagnosis, as well as musculoskeletal, psychiatric, cardiovascular or respiratory diagnoses. The population-based design made it possible to examine dose-response and potential gender differences in the associations.

METHODS

About 1.8 million men and women aged 44-63 years and registered as living in Sweden in 2005 were followed regarding disability pension during 2006-2016, until ages 55-65 years. Mean values of physical workload and job control, estimated through gender-specific job-exposure matrices (JEMs), were assigned to individuals through their occupational titles in 2005. Exposure values were ranked separately for women and men and divided into quintiles. Associations were analyzed with Cox proportional-hazards regression.

RESULTS

The analyses showed robust, dose-response associations between physical workload and disability pension with a musculoskeletal diagnosis in both genders: the adjusted hazard ratio and 95% confidence interval for those with the heaviest exposure was 2.58 (2.37-2.81) in women and 3.34 (2.83-3.94) in men. Dose-response associations were also seen in relation to disability pension with a cardiovascular or a respiratory diagnosis, though the hazard ratios were smaller. Physical workload was not associated with disability pension with a psychiatric diagnosis after adjustment for job control.

CONCLUSION

This study of the entire Swedish population of middle-aged and older workers suggests that higher degrees of physical workload may increase the risk of disability pension overall, and specifically with musculoskeletal, cardiovascular or respiratory diagnosis, in both women and men.

Dangers of residual confounding: a cautionary tale featuring cognitive ability, socioeconomic background, and education

BACKGROUND

Cognitive ability and socioeconomic background (SEB) have been previously identified as determinants of achieved level of education. According to a "discrimination hypothesis", higher cognitive ability is required from those with lower SEB in order to achieve the same level of education as those with higher SEB. Support for this hypothesis has been claimed from the observation of a positive association between SEB and achieved level of education when adjusting for cognitive ability. We propose a competing hypothesis that the observed association is due to residual confounding.

METHODS

To adjudicate between the discrimination and the residual confounding hypotheses, data from the 1997 National Longitudinal Survey of Youth (NLSY97, N = 8984) was utilized, including a check of the logic where we switched predictor and outcome variables.

RESULTS

The expected positive association between SEB and achieved level of education when adjusting for cognitive ability (predicted by both hypotheses) was found, but a positive association between cognitive ability and SEB when adjusting for level of education (predicted only by the residual confounding hypothesis) was also observed.

CONCLUSIONS

These results highlight the potential use of reversing predictors and outcomes to test the logic of hypothesis testing, and support a residual confounding hypothesis over a discrimination hypothesis in explaining associations between SEB, cognitive ability, and educational outcome.

Psychosocial working conditions and the risk of diagnosed depression: a Swedish register-based study

BACKGROUND

High job demands, low job control, and their combination (job strain) may increase workers' risk of depression. Previous research is limited by small populations, not controlling for previous depression, and relying on the same informant for reporting exposure and outcome. This study aims to examine the relationship between objectively measured workplace factors and the risk of developing clinical depression among the Swedish working population while controlling for previous psychiatric diagnoses and sociodemographic factors.

METHODS

Control, demands, and job strain were measured using the Swedish Job Exposure Matrix (JEM) measuring psychosocial workload linked to around 3 million individuals based on their occupational titles in 2005. Cox regression models were built to estimate associations between these factors and diagnoses of depression recorded in patient registers.

RESULTS

Lower job control was associated with an increased risk of developing depression (HR 1.43, 95% CI 1.39-1.48 and HR 1.27, 95% CI 1.24-1.30 for men and women with the lowest control, respectively), and this showed a dose-response relationship among men. Having high job demands was associated with a slight decrease in depression risk for men and women. High strain and passive jobs (both low control jobs) were associated with an increased risk of depression among men, and passive jobs were associated with an increased risk among women.

CONCLUSION

High job control appears important for reducing the risk of developing depression even when accounting for previous psychiatric diagnoses and sociodemographic factors. This is an important finding concerning strategies to improve occupational and in turn mental health.

Early life programming of adult ischemic heart disease within and across generations: The role of the socioeconomic context

BACKGROUND

The developmental origins of ischemic heart disease (IHD) have been widely documented but little is known about their persistence across more than one generation. This study aimed to investigate whether the effects of early life disadvantages on adult IHD have changed between generations and are mediated by adult socioeconomic circumstances, and further explore the transgenerational effects of grandparental and parental exposures to disadvantaged circumstances on adult offspring's IHD.

METHODS

We used register-based data from the Uppsala Multigenerational Study, Sweden. The study populations were the parents born 1915-1929 and their offspring born 1932-1972 with available obstetric data. The offspring were further linked to grandparents who had their socioeconomic and demographic data recorded. The outcome was incident IHD assessed at ages 32-75 during a follow-up from January 1, 1964 till December 31, 2008. The exposures included birthweight standardized-for-gestational age, ponderal index, gestational length, and parental socioeconomic position (SEP). Education and income were analyzed as mediators. Potential transgenerational associations were explored by linking offspring IHD to parents' standardized birthweight and gestational length, grandparental SEP, and to grandmothers' age, parity, and marital status at parental birth. All associations were examined in Cox proportional hazard regression models.

RESULTS

Lower standardized birthweight and lower parental SEP were found to be associated with higher IHD rates in both generations, with no evidence of effect modification by generation. Education and income did not mediate the association between standardized birthweight and IHD. Disadvantaged grandparental SEP, younger and older childbearing ages of grandmothers, and paternal preterm birth affected offspring's IHD independent of parental education, income, or IHD history.

CONCLUSIONS

The findings point to similar magnitudes of IHD inequalities by early life disadvantages across two historical periods and the existence of transgenerational effects on IHD. Epigenetic dysregulation involving the germline is a plausible candidate mechanism underlying the transgenerational associations that warrant further research.

A comparison of models with weight, height, and BMI as predictors of mortality

Introduction

Body mass index (BMI) is a composite variable of weight and height, often used as a predictor of health outcomes, including mortality. The main purpose of combining weight and height in one variable is to obtain a measure of obesity independent of height. It is however unclear how accurate BMI is as a predictor of mortality compared with models including both weight and height or a weight × height interaction as predictors.

Methods

The current study used conscription data on weight, height, and BMI of Swedish men (N = 48,904) in 1969/70 as well as linked data on mortality (3442 deaths) between 1969 and 2008. Cox proportional hazard models including combinations of weight, height, and BMI at conscription as predictors of subsequent all-cause and cause-specific mortality were fitted to data.

Results

An increase by one standard deviation on weight and BMI were associated with an increase in hazard for all-cause mortality by 5.4% and 11.5%, respectively, while an increase by one standard deviation on height was associated with a decrease in hazard for all-cause mortality by 9.4%. The best-fitting model indicated lowest predicted all-cause mortality for those who weighed 60.5 kg at conscription, regardless of height. Further analyses of cause-specific mortality suggest that this weight seems to be a compromise between lower optimal weights to avoid cancer and CVD mortality and a higher optimal weight to not die by suicide.

Conclusions

According to the present findings, there are several ways to make better use of measured weight and height than to calculate BMI when predicting mortality.

How intelligence and emotional control are related to suicidal behavior across the life course - A register-based study with 38-year follow-up

BACKGROUND

Both low intelligence and low emotional control have previously been linked to a higher risk of suicide, but it is unknown whether the associations apply consistently over the life course.

METHODS

The study was based on data on intelligence and emotional control, collected from 48 738 Swedish men conscripted in 1969-1970, at ages 18-20 years. The data were linked to national registers giving information on subsequent suicidal behavior (completed and attempted suicide) up to the age of 59 years. The associations were investigated using logistic regression and Cox proportional hazards regression models, with adjustment for childhood socioeconomic status.

RESULTS

Intelligence and emotional control assessed in late adolescence both showed robust inverse associations with suicidal behavior over the 38-year follow-up. However, while the association between lower intelligence and higher rate of suicidal behavior remained the same throughout (~40% increased hazard per unit on a five-level scale), the association between lower emotional control and suicidal behavior was substantially stronger in early adulthood (~100% increased hazard per unit) than in late middle age (~30% increased hazard per unit).

CONCLUSIONS

The study adds to previous research by showing that the association between poor emotional control and subsequent suicide risk in men becomes weaker over the life course, while the association between low intelligence and suicide risk seems to be constant. The particularly high suicide risk of young men with poor emotional control may motivate targeted prevention efforts.

Academic performance, subsequent socioeconomic status and suicide attempt in adulthood: path analyses on Swedish cohort data

BACKGROUND

Poor academic performance in childhood is associated with suicide attempt in adulthood, but the mechanisms are not known. We investigated educational attainment as a possible pathway.

METHODS

We followed two sets of cohorts, born around 1950/1970, respectively, in the Swedish population-representative 'Evaluation Through Follow-up' study for a first suicide attempt in national records up to 2013. Data on grade point average (GPA) at age 13/16 and educational attainment (years of schooling) in adulthood were used. The path models included linear and Cox proportional hazards regressions. A model with matched age range during follow-up was used to compare the cohorts.

RESULTS

In the 1970 cohort, the association between GPA and suicide attempt between age 26 and 46 was partly mediated by attained education (total association, β=-0.82; via education: -0.29, per SD increase in GPA), but GPA also had a direct path to suicide attempt (β=-0.53). There was no evidence of such a pathway in the 1950 cohort between age 41 and 65. In the age-matched analysis, at age 26-46, the association between GPA and suicide attempt was stronger in the 1970 cohort compared to the 1950 cohort (β=-0.72 and -0.24, respectively).

CONCLUSIONS

Differences in attained education seem to partly explain the associations of academic performance with suicide attempt up to middle age. Furthermore, there is some indication that academic performance may have become more important for young people's mental health than it was in previous generations.

Social and Psychological Predictors of Body Mass Index among South Africans 15 Years and Older: SANHANES-1

This study investigated how psychological distress and the proxies for social position combine to influence the risk of both underweight and overweight in South Africans aged 15 years and older. This was a cross-sectional study that included 2254 men and 4170 women participating in the first South African National Health and Nutrition Examination Survey (SANHANES-1). An analysis exploring the associations of social and mental health characteristics with body mass index (BMI) was conducted using binary and multinomial logistic regressions. Results suggested that, overall, women had a higher risk of overweight/obesity compared to men (age-adjusted odds ratio [AOR] 4.65; 95% confidence intervals [CI] 3.94–5.50). The gender effect on BMI was smaller in non-African participants (AOR 3.02; 95% CI 2.41–3.79; p-value for interaction = 0.004). Being employed and having a higher level of education were associated with higher risks of overweight and obesity and a lower risk of underweight. Being single or without a spouse and poor mental health were found to increase the odds of being underweight, especially in men. To conclude, there are strong social gradients and important gender and ethnic differences in how BMI is distributed in the South African population.

Early life socioeconomic position and mortality from cardiovascular diseases: an application of causal mediation analysis in the Stockholm Public Health Cohort

OBJECTIVE

We aimed to quantify the mediating impact of adult social and behavioural mechanisms in the association between childhood socioeconomic position (SEP) and cardiovascular disease (CVD) mortality by employing a weighting approach to mediation analysis.

DESIGN

Prospective cohort study.

SETTING

Stockholm County, Sweden.

PARTICIPANTS

19 720 individuals who participated in the Stockholm Public Health Cohort survey in 2002 and were older than 40 years.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome was CVD mortality. Non-CVD mortality was additionally analysed for comparison.

METHODS

Study subjects were followed in routine registers from 2002 to 2011 for mortality. Data on father's SEP and adult social and behavioural factors came from questionnaire survey. The inverse odds weighting method was used to estimate the total effect, the natural direct effect and the natural indirect effect (NIE) in Poisson regression models. All results were adjusted for gender, age, country of birth and marital status. Multiple imputation was used to handle missing data.

RESULTS

The total effect of manual versus non-manual father's SEP on CVD mortality was estimated as an incidence rate ratio (IRR) of 1.24 (95% CI 1.09 to 1.41). When the social and behavioural factors were accounted for, the IRR for the NIE was 1.09 (95% CI 1.04 to 1.14), suggesting a mediation of 44% of the total effect. As for non-CVD mortality, father's manual SEP was associated with 1.15 fold excess risk (IRR: 1.15; 95% CI 1.04 to 1.27) of which the effect represented by the whole set of mediators was 1.06 (95% CI 1.01 to 1.10).

CONCLUSION

Adult social and behavioural factors had a considerable mediating effect on the early life social origin of mortality from CVDs and other causes. Future research employing causal mediation analysis may nevertheless have to consider additional factors for a fuller understanding of the mechanisms.

Fathers' Alcohol Consumption and Long-Term Risk for Mortality in Offspring

Aim

This study examined associations between fathers’ alcohol consumption and risk for total and cause-specific mortality in offspring.

Short summary

We examined the associations between fathers’ alcohol consumption and total and cause-specific mortality in adult offspring. Fathers’ alcohol consumption was associated with increased risk of alcohol-related mortality in offspring. The association appeared to be weaker for causes of death in which alcohol plays a smaller, or less direct, role.

Methods

Data on fathers’ alcohol consumption, and offspring’s risky use of alcohol, smoking, mental health and contact with police/childcare authorities were collected among 46,284 men (sons) aged 18–20 years, during conscription for compulsory military training in 1969/70. Data on offspring mortality were obtained from the National Cause of Death register, 1971–2008. The mortality outcomes included total mortality, alcohol-related causes of death and violent causes of death (categorized into suicides vs violent/external causes excluding suicides).

Results

Compared to sons whose fathers never used alcohol, the risk for total and alcohol-related mortality among sons increased with the father’s consumption level. The risk of violent death was significantly elevated among sons whose fathers drank alcohol occasionally or often, but the risk of suicide increased in the highest consumption category only. After adjustment for covariates, the results remained for alcohol-related mortality whereas they were significantly attenuated, or disappeared, for total mortality, violent death and suicide.

Conclusions

Fathers’ alcohol consumption is associated with increased risk of alcohol-related mortality in the offspring. Alcohol use among fathers also increases the offspring’s risk of later total mortality, suicide and violent death, but these associations appear to be mediated or confounded by factors related to parental drinking and/or adverse childhood psychosocial circumstances.

Cognitive and emotional outcomes after prolonged education: a quasi-experiment on 320 182 Swedish boys

Background: Cognitive and socio-emotional abilities are powerful predictors of death and disease as well as of social and economic outcomes. Education is societies’ main way of promoting these abilities, ideally so that inequalities by socioeconomic background are reduced. However, the extent to which education serves these cognitive, social-emotional and equality objectives is relatively unknown and intensively debated. Drawing on a Swedish school reform that was explicitly designed as a massive quasi-experiment, we assessed differential impact of education on intelligence and emotional control across childhood socioeconomic position. We also assessed initial differences in abilities by childhood socioeconomic position and how well childhood socioeconomic position and abilities predict all-cause mortality.

Methods: The Swedish comprehensive school reform, rolled out during the 1950s, extended compulsory education from 8 to 9 years in some municipalities whereas others were kept as controls for the sake of evaluation. We followed eight full cohorts of Swedish boys born between 1951 and 1958, who lived in 1017 municipalities with known experimental status (344 336 boys) and whose childhood socioeconomic position was known (320 182 boys). At conscription, intelligence was measured by four subtests and emotional control (calm and efficient responses in various situations) was rated by a military psychologist. Both measures were standardized to have a mean of 100 and standard deviation of 15. All-cause mortality was recorded until 49–56 years of age.

Results: The reform had an average positive impact on intelligence of 0.75 IQ units (95% confidence interval (CI): 0.54, 0.97; P < 0.0005). The impact on emotional control was negative; −0.50 units (95% CI: −0.72, −0.28; P < 0.0005). Both effects differed by socioeconomic background so that the average IQ difference between sons of high non-manual and unqualified manual workers was reduced from 16.32 to 15.57 units and the difference in emotional control was reduced from 6.50 to 5.63 units. All-cause mortality was predicted by low childhood socioeconomic position [hazard ratio (HR) = 1.15 [95% CI: 1.11, 1.20], P < 0.0005], low intelligence [HR = 1.39 (95% CI: 1.34, 1.44), P < 0.0005] as well as low emotional control [HR = 1.61 (95% CI: 1.55, 1.67), P < 0.0005] in mutually adjusted models.

Conclusions: Extending compulsory education promoted intelligence but lowered emotional control, and reduced disparities over social background in both. Emotional control was the strongest predictor of all-cause mortality. Our results are in line with the idea that education is important in our efforts to achieve healthy, competent and fair societies, but much more work is needed to understand the links between education and non-cognitive skills.

Suicide attempt predicted by academic performance and childhood IQ: a cohort study of 26 000 children

OBJECTIVE

Academic performance in youth, measured by grade point average (GPA), predicts suicide attempt, but the mechanisms are not known. It has been suggested that general intelligence might underlie the association.

METHODS

We followed 26 315 Swedish girls and boys in population-representative cohorts, up to maximum 46 years of age, for the first suicide attempt in hospital records. Associations between GPA at age 16, IQ measured in school at age 13 and suicide attempt were investigated in Cox regressions and mediation analyses.

RESULTS

There was a clear graded association between lower GPA and subsequent suicide attempt. With control for potential confounders, those in the lowest GPA quartile had a near five-fold risk (HR 4.9, 95% CI 3.7-6.7) compared to those in the highest quartile. In a mediation analysis, the association between GPA and suicide attempt was robust, while the association between IQ and suicide attempt was fully mediated by GPA.

CONCLUSIONS

Poor academic performance in compulsory school, at age 16, was a robust predictor of suicide attempt past young adulthood and seemed to account for the association between lower childhood IQ and suicide attempt.

Higher IQ in childhood is linked to a longer life

New data on cause of death suggest the link is mediated by risk factors such as smoking

Cannabis, Tobacco, Alcohol Use, and the Risk of Early Stroke: A Population-Based Cohort Study of 45 000 Swedish Men

BACKGROUND AND PURPOSE

Current knowledge on cannabis use in relation to stroke is based almost exclusively on clinical reports. By using a population-based cohort, we aimed to find out whether there was an association between cannabis use and early-onset stroke, when accounting for the use of tobacco and alcohol.

METHODS

The cohort comprises 49 321 Swedish men, born between 1949 and 1951, who were conscripted into compulsory military service between the ages of 18 and 20. All men answered 2 detailed questionnaires at conscription and were subject to examinations of physical aptitude, psychological functioning, and medical status. Information on stroke events up to ≈60 years of age was obtained from national databases; this includes strokes experienced before 45 years of age.

RESULTS

No associations between cannabis use in young adulthood and strokes experienced ≤45 years of age or beyond were found in multivariable models: cannabis use >50 times, hazard ratios=0.93 (95% confidence interval [CI], 0.34-2.57) and 0.95 (95% CI, 0.59-1.53). Although an almost doubled risk of ischemic stroke was observed in those with cannabis use >50 times, this risk was attenuated when adjusted for tobacco usage: hazards ratio=1.47 (95% CI, 0.83-2.56). Smoking ≥20 cigarettes per day was clearly associated both with strokes before 45 years of age, hazards ratio=5.04 (95% CI, 2.80-9.06), and with strokes throughout the follow-up, hazards ratio=2.15 (95% CI, 1.61-2.88).

CONCLUSIONS

We found no evident association between cannabis use in young adulthood and stroke, including strokes before 45 years of age. Tobacco smoking, however, showed a clear, dose-response shaped association with stroke.

Prevalence, co-occurrence, and clustering of health-risk behaviors among people with different socio-economic trajectories: A population-based study

Only a few previously published studies have investigated the co-occurrence and clustering of health-risk behaviors in people with different socio-economic trajectories from childhood to adulthood. This study was based on data collected through the Stockholm County Council's public health surveys. We selected the 24,241 participants aged 30 to 65years, who responded to a postal questionnaire in 2010. Information on parents' and participants' educational levels was used for classification of four socio-economic trajectories, from childhood to adulthood: the 'stable high', the 'upwardly mobile', the 'downwardly mobile', and the 'stable low'. Information on daily smoking, risky drinking, physical inactivity, and poor diet was used for assessment of health-risk behaviors: their prevalence, co-occurrence, and clustering. We found all health-risk behaviors to be more prevalent among women and men with a downwardly mobile or stable low socio-economic trajectory. Accordingly, having three or four co-occurring health-risk behaviors were much more likely (up to 4 times, in terms of odds ratios) in these groups as compared to the women and men with an upwardly mobile or a stable high socio-economic trajectory. However, clustering of the health-risk behaviors was not found to be stronger in those with a downwardly mobile or stable low socio-economic trajectory. Thus, the fact that women and men with a disadvantageous socio-economic career were found to have co-occurring health-risk behaviors more often than people with an advantageous socio-economic career seemed to be generated by differences in prevalence of the health-risk behaviors, not by differences in clustering of the behaviors.

Cannabis use among Swedish men in adolescence and the risk of adverse life course outcomes: results from a 20 year-follow-up study

AIMS

To examine associations between cannabis use in adolescence (at age 18) and unemployment and social welfare assistance in adulthood (at age 40) among Swedish men.

DESIGN

Longitudinal cohort study.

SETTING AND PARTICIPANTS

A total of 49.321 Swedish men born in 1949-51, who were conscripted to compulsory military service at 18-20 years of age.

MEASUREMENTS

All men answered two detailed questionnaires at conscription and were subject to examinations of physical aptitude psychological functioning and medical status. By follow-up in national databases, information on unemployment and social welfare assistance was obtained.

FINDINGS

Individuals who used cannabis at high levels in adolescence had increased risk of future unemployment and of receiving social welfare assistance. Adjusted for all confounders (social background, psychological functioning, health behaviours, educational level, psychiatric diagnoses), an increased relative risk (RR) of unemployment remained in the group reporting cannabis use > 50 times [RR = 1.26, 95% confidence interval (CI) = 1.04-1.53] only. For social welfare assistance, RR in the group reporting cannabis use 1-10 times was 1.15 (95% CI = 1.06-1.26), RR for 11-50 times was 1.21 (95% CI = 1.04-1.42) and RR for > 50 times was 1.38 (95% CI = 1.19-1.62).

CONCLUSIONS

Heavy cannabis use among Swedish men in late adolescence appears to be associated with unemployment and being in need of social welfare assistance in adulthood. These associations are not explained fully by other health-related, social or behavioural problems.

Intelligence and Disability Pension in Swedish Men and Women Followed from Childhood to Late Middle Age

OBJECTIVE

To investigate the association between intelligence and disability pension due to mental, musculoskeletal, cardiovascular, and substance-use disorders among men and women, and to assess the role of childhood social factors and adulthood work characteristics.

METHODS

Two random samples of men and women born 1948 and 1953 (n = 10 563 and 9 434), and tested for general intelligence at age 13, were followed in registers for disability pension until 2009. Physical and psychological strains in adulthood were assessed using job exposure matrices. Associations were examined using Cox proportional hazard regression models, with increases in rates reported as hazard ratios (HRs) with 95% confidence intervals (95%CI) per decrease in stanine intelligence.

RESULTS

In both men and women increased risks were found for disability pension due to all causes, musculoskeletal disorder, mental disorder other than substance use, and cardiovascular disease as intelligence decreased. Increased risk was also found for substance use disorder in men. In multivariate models, HRs were attenuated after controlling for pre-school plans in adolescence, and low job control and high physical strain in adulthood. In the fully adjusted model, increased HRs remained for all causes (male HR 1.11, 95%CI 1.07-1.15, female HR 1.06, 95%CI 1.02-1.09) and musculoskeletal disorder (male HR 1.16, 95%CI 1.09-1.24, female HR 1.08, 95%CI 1.03-1.14) during 1986 to 2009.

CONCLUSION

Relatively low childhood intelligence is associated with increased risk of disability pension due to musculoskeletal disorder in both men and women, even after adjustment for risk factors for disability pension measured over the life course.

Does high intelligence improve prognosis? The association of intelligence with recurrence and mortality among Swedish men with coronary heart disease

BACKGROUND

Lower intelligence early in life is associated with increased risks for coronary heart disease (CHD) and mortality. Intelligence level might affect compliance to treatment but its prognostic importance in patients with CHD is unknown.

METHODS

A cohort of 1923 Swedish men with a measure of intelligence from mandatory military conscription in 1969-1970 at age 18-20, who were diagnosed with CHD 1991-2007, were followed to the end of 2008.

PRIMARY OUTCOME

recurrent CHD event. Secondary outcome: case fatality from the first event, cardiovascular and all-cause mortality. National registers provided information on CHD events, comorbidity, mortality and socioeconomic factors.

RESULTS

The fully adjusted HRs for recurrent CHD for medium and low intelligence, compared with high intelligence, were 0.98, (95% CIs 0.83 to 1.16) and 1.09 (0.89 to 1.34), respectively. The risks were increased for cardiovascular and all-cause mortality with lower intelligence, but were attenuated in the fully adjusted models (fully adjusted HRs for cardiovascular mortality 1.92 (0.94 to 3.94) and 1.98 (0.89 to 4.37), respectively; for all-cause mortality 1.63 (1.00 to 2.65) and 1.62 (0.94 to 2.78), respectively). There was no increased risk for case-fatality at the first event (fully adjusted ORs 1.06 (0.73 to 1.55) and 0.97 (0.62 to 1.50), respectively).

CONCLUSIONS

Although we found lower intelligence to be associated with increased mortality in middle-aged men with CHD, there was no evidence for its possible effect on recurrence in CHD.

Body mass index in young adulthood and suicidal behavior up to age 59 in a cohort of Swedish men

An association of higher body mass index (BMI) with lower risk of attempted and completed suicide has been reported. In contrast, increasing BMI has been found to be associated with depression and other risk factors for suicidal behavior. We aimed to investigate this possible paradox in a cohort comprising 49 000 Swedish men. BMI, mental health, lifestyle and socioeconomic measures were recorded at conscription in 1969-70, at ages 18-20. Information on attempted suicide 1973-2008 and completed suicide 1971-2008 was obtained from national records. Hazard ratios (HR) were estimated by Cox proportional hazard models. We found that each standard deviation (SD) increase in BMI was associated with a 12% lower risk of later suicide attempt (HR 0.88, 95% CI 0.83-0.94). Associations were somewhat weaker for completed suicide and did not reach conventional levels of statistical significance (HR 0.93, 95% CI 0.85-1.01). Adjustment for a wide range of possible confounding factors had little effect on the associations. Lower BMI at conscription was also associated with higher prevalence of psychiatric diagnoses, low emotional control and depressed mood. Our results confirm previous findings regarding the association of higher BMI with a reduced risk of suicide, extending them to show similar findings in relation to suicide attempts. The associations were little affected by adjustment for a range of possible confounding factors. However, we found no evidence that high BMI was associated with an increased risk of depression cross-sectionally or longitudinally.