Karina Corbett

Impact of aerobic fitness on musculoskeletal sickness absence 5-15 years later: a cohort study of 227,201 male Norwegian employees.

Objectives The aim of the study was to estimate associations between aerobic fitness among men at age 18–19 years and work absence due to musculoskeletal sickness 5–15 years later. Methods All 321 975 men born between 1967 and 1976 in Norway were identified and followed up in several national registers. Men who completed an aerobic fitness test at military conscription during 1985–1995 (N=227 201) were followed from 2000 through 2003 with respect to a first musculoskeletal absence. Cox regression was conducted to estimate HRs between aerobic fitness (high, medium, poor) and musculoskeletal absence. Results A total of 26 061 men had a musculoskeletal absence (absolute risk 0.115). Absence was associated with fitness level. Associations were confounded by other conscript characteristics (intellectual capacity, body mass index, musculoskeletal condition) and parental education level and were restricted to non-injury absence. With high fitness as reference, the adjusted non-injury HR estimates were 1.18 (95% CI 1.12 to 1.24) and 1.39 (1.31 to 1.47) for medium and poor fitness, respectively. Poor fitness men were more likely to achieve low educational attainment and employment in high-absence industries and enterprises. The impact of intellectual capacity and parental education level on absence was considerably larger than the effect from fitness. A subset analysis with fitness data of better quality yielded moderately stronger associations. Conclusions Aerobic fitness among conscripts was moderately associated with non-injury musculoskeletal absence 5–15 years later. However, the overall impact of intellectual capacity and parental education appears to be greater than that of aerobic fitness.

Adult social position and sick leave: the mediating effect of physical workload.

OBJECTIVE This study aimed to quantify how much of the adult social gradient in sick leave can be attributed to the mediating role of physical workload while accounting for the role of childhood and adolescent social position and neuroticism. METHODS Our sample consisted of 2099 women and 1229 men from a Norwegian birth cohort study (born 1967-1976) who participated in the Nord-Trøndelag Health Study (2006-2008) (HUNT3). Data on sick leave (defined as >16 calendar days; 2006-2009) and social position during childhood, adolescence, and adulthood were obtained from national registers. Study outcome was time-to-first sick leave spell. Physical workload and neuroticism were self-reported in HUNT3. Mediating effects through physical workload were estimated using a method based on the additive hazards survival model. RESULTS A hypothetical change from highest to lowest group in adult social position was, for women, associated with 51.6 [95% confidence interval (95% CI) 24.7-78.5] additional spells per 100,000 person-days at risk, in a model adjusted for childhood and adolescent social position and neuroticism. The corresponding rate increase for men was 41.1 (95% CI 21.4-60.8). Of these additional spells, the proportion mediated through physical workload was 24% (95% CI 10-49) and 30% (95% CI 10-63) for women and men, respectively. CONCLUSIONS The effect of adult social position on sick leave was partly mediated through physical workload, even while accounting for earlier life course factors. Our findings provide support that interventions aimed at reducing physical workload among those with lower adult social position could reduce sick leave risk.

0281 The relationship between socioeconomic position, working conditions and sickness absence in a life-course perspective

Objectives Socioeconomic position (SEP) in childhood and in adulthood, and work environment factors are predictors of sickness absence (SA). Our objective was to examine the relationships between these factors in a life-course perspective, which has hardly been done previously. Method Our study sample was all employed individuals who partook in the HUNT study and who were born between 1967 and 1976 (N = 4530). Outcome was the risk of at least one SA episode in 2009. Educational attainment (5 categories) served as indicator of adult SEP, whereas highest parental education level and father’s average income during early childhood (0–6 years) were indicators of childhood SEP. Work factors were job control, physically demanding work and shift work. Risk ratios (RRs) were estimated using Poisson regression. Results 29% of the women and 17% of the men had SA during follow-up. There was a strong gradient according to adult SEP for both genders. The age-adjusted RR for having an SA episode, comparing highest and lowest educational levels, was 2.83 for women and 3.85 for men. The RR was marginally weakened in women (-4%) and strengthened in men (+18%), after adjusting for childhood SEP (Model 2). Including all work factors in the model reduced the RRs by 20% compared to Model 2 (RR 2.20 and 3.62, respectively), the largest impact for physically demanding work (15% reduction in RR). Conclusions There were strong social gradients in SA, partly mediated through work environment factors in a life-course perspective. We found gender differences that are difficult to explain.

Kristensen et al. Respond to “High Birth Weight and Later Health”

We thank Dr. Eriksen (1) for his thorough and useful comments on our article (2). His commentary covers not only high birth weight and intelligence, which was the topic of our article, but also more general aspects of the role of birth weight on processes determining later health. The commentary addresses 3 important methodological challenges: confounding from nonshared factors in sibling analysis, disentangling influences from prenatal and postnatal processes, and uncovering the true role of birth weight associations. These issues are well reviewed, and we agree with Dr. Eriksen on all 3 points. One major advantage of sibling analysis is that it allows for the effective control of genetic and environmental factors shared by the siblings (3). Frisell et al. (4) have, however, showed that sibling-based estimates are more biased from nonshared confounders than are estimates from individual analysis if siblings are less similar with regard to the confounders than to the exposure.

1410 Cause-specific sickness absence by occupation

Introduction To identify workers facing particular challenges related to occupational exposure and health is valuable, as work environment plays an important role in terms of sickness absence (SA) and return to work. Assessing vulnerable occupational groups related to SA may facilitate decision makers in terms of allocating resources and interventions. The aim of this paper was to assess cause-specific SA rates by occupation and evaluate occupational specific excess fractions for SA. Methods The source population was a Norwegian birth cohort (all 626 928 live-born individuals born between 1967 and 1976). Individual records on physician-diagnosed SA spells lasting >16 calendar days were obtained from the Norwegian event database FD-Trygd. The incidence rate of SA was estimated annually during 2005–2009. SA with musculoskeletal and mental diagnoses, was estimated for 31 occupational groups classified by ISCO-88 on a 2-digit level. Excess cause-specific SA was also estimated for each of the 31 occupations. All analyses were stratified by gender. Result Workers in sales and service occupations and metal and machinery workers had the highest annual rates of musculoskeletal SA. Male metal and machinery workers had a 91% increased rate, compared to male corporate managers, while female workers in sales and services occupations had an 83% increased rate, compared to female corporate managers. For SA related to mental disorders, personal care workers had the highest rates among both men and women. Discussion Occupation is an imprecise measure of work exposure and in the continued work on these data we will use a newly developed job exposure matrix to estimate the associations between specific physical and psychosocial exposures and cause-specific sickness absence by occupation.

The impact of completing upper secondary education - a multi-state model for work, education and health in young men

BackgroundCompleting upper secondary education is associated with higher work participation and less health-related absence from work. Although these outcomes are closely interrelated, most studies focus on single outcomes, using cross-sectional designs or short follow-up periods. As such, there is limited knowledge of the long-term outcomes, and how paths for completers and non-completers unfold over time. In this paper, we use multi-state models for time-to-event data to assess the long-term effects of completing upper secondary education on employment, tertiary education, sick leave, and disability pension over twelve and a half years for young men.MethodsBaseline covariates and twelve and a half years of follow-up data on employment, tertiary education, sick leave and disability pension were obtained from national registries for all males born in Norway between 1971 and 1976 (n =184951). The effects of completing upper secondary education (by age 23) were analysed in a multi-state framework, adjusting for both individual and family level confounders. All analyses were done separately for general studies and vocational tracks.ResultsCompleters do better on a range of outcomes compared to non-completers, for both fields of upper secondary education, but effects of completion change over time. The largest changes are for tertiary education and work, with the probability of work increasing reciprocally to the probability of education. Vocational students are quicker to transfer to the labour market, but tend to have more unemployment, sick leave and disability, and the absolute effects of completion on these outcomes are largest for vocational tracks. However, the relative effects of completion are larger for general studies.ConclusionCompleting upper secondary education increases long-term work participation and lowers health-related absence for young men, but effects diminish over time. Studies that have used shorter follow-up periods could be overstating the negative effects of dropout on labour market participation. Multi-state models are well suited to analyse data on work, education and health-related absence, and can be useful in understanding the dynamic aspects of these outcomes.

High birth weight and perinatal mortality among siblings. A register based study in Norway, 1967-2011

Background Perinatal mortality according to birth weight has an inverse J-pattern. Our aim was to estimate the influence of familial factors on this pattern, applying a cohort sibling design. We focused on excess mortality among macrosomic infants (>2 SD above the mean) and hypothesized that the birth weight-mortality association could be explained by confounding shared family factors. We also estimated how the participant’s deviation from mean sibling birth weight influenced the association. Methods and findings We included 1 925 929 singletons, born term or post-term to mothers with more than one delivery 1967–2011 registered in the Medical Birth Registry of Norway. We examined z-score birth weight and perinatal mortality in random-effects and sibling fixed-effects logistic regression models including measured confounders (e.g. maternal diabetes) as well as unmeasured shared family confounders (through fixed effects models). Birth weight-specific mortality showed an inverse J-pattern, being lowest (2.0 per 1000) at reference weight (z-score +1 to +2) and increasing for higher weights. Mortality in the highest weight category was 15-fold higher than reference. This pattern changed little in multivariable models. Deviance from mean sibling birth weight modified the mortality pattern across the birth weight spectrum: small and medium-sized infants had increased mortality when being smaller than their siblings, and large-sized infants had an increased risk when outweighing their siblings. Maternal diabetes and birth weight acted in a synergistic fashion with mortality among macrosomic infants in diabetic pregnancies in excess of what would be expected for additive effects. Conclusions The inverse J-pattern between birth weight and mortality is not explained by measured confounders or unmeasured shared family factors. Infants are at particularly high mortality risk when their birth weight deviates substantially from their siblings. Sensitivity analysis suggests that characteristics related to maternal diabetes could be important in explaining the increased mortality among macrosomic infants.

0246 The impact of high-school completion - a multi-state model for work participation and health-related absence in young men

Withdrawn at the author’s request

0182 High school dropout and cause-specific mortality in young adulthood: the mediating role of work career

Objectives High school dropout has unfavourable consequences. We examine the association between dropout and mortality and estimate the mediating role of an unfavourable work trajectory. Methods Subjects born in Norway 1967–1976 were followed up in several national registries. The association between dropping out of high school by age 23 and all-cause and cause-specific mortality 10 years onwards were estimated as hazard ratios (HR), applying Cox regression in confounder-adjusted models. Characteristics relating to different trajectories during follow-up were considered as mediators of dropout effects on survival. Results Thirty-nine percent out of 396 373 participants were classified as dropouts. All-cause mortality during follow-up was 69 per 1 00 000 person-years (2689 cases). The crude dropout HR was 2.1 (1.9–2.3), being reduced to 1.8 (1.6–2.0) in the confounder-adjusted model. After including the potential mediators in the model, dropouts no longer had an excess mortality compared to non-dropouts (HR 1.0, CI (0.9–1.1)). Mediators relating to financial situation, social benefits and employment accounted for the largest reduction in the association. Deaths caused by overdose and drug dependence were strongly associated with dropout (454 cases; rate 12; confounder-adjusted HR 5.0 (3.8–6.5)). Inclusion of work trajectory factors attenuated the association by 63% (women) and 48% (men). Conclusions Mortality was clearly associated with high school dropout, strongest for drug-related causes. The results suggest that an unfavourable work career following high school dropout could be an important mechanism for this association.

0213 The impact of the norwegian cooperation agreement on a more inclusive working life (ia agreement) on sickness absence and disability pensioning

Background Increasing work participation is an important political objective in many countries. In Norway, a voluntary national intervention program aimed at increasing work participation (the IA Agreement) was implemented in 2001, and is still ongoing. One of the main goals of the IA Agreement is to reduce sickness absence (SA) and disability pensions (DP). Organisations that sign the agreement commit themselves to take active measures in order to reduce SA and DP, and in return, they are given special rights such as grants for workplace adjustments and job training. Scientific evaluations of the IA Agreement have been limited. We aim to estimate the impact of the IA Agreement on SA and DP in Norway during 2001–2009. Methods The source population is a national cohort of all 626 928 individuals born 1967–1976. Individual-level data on SA, DP, employment, and background characteristics were obtained from national registries. We apply a quasi-experimental design using difference-in-difference analysis, comparing employees in IA organisations (intervention group) with employees in non-IA organisations (control group), with respect to pre-post differences in SA and DP. Results The IA Agreement was signed by 13 760 organisations by March 2003 and covered 43% of Norwegian employees. Compared to the general working population, IA organisations had a higher proportion of women and workers in the healthcare sector. We will analyse the nationwide impact of the IA Agreement on SA and DP and explore differences by gender, industry and diagnostic category.