S2.1 Do working conditions influence cognitive decline, brain structural changes and risk of dementia?
Chair: Kirsten Nabe-Nielsen
Being occupationally active may serve to preserve cognitive health in old age, e.g. through participation in cognitively and socially stimulating activities. Yet, being occupational active may also imply exposure to psychosocial stressors with a potentially negative effect on cognitive health. The aim of this symposium is to explore the role of working conditions on cognitive decline, brain structural changes, and the risk of dementia in old age. The studies presented use Danish and Swedish data from questionnaires, clinical examinations, brain imaging, and registers. Thus, the audience is introduced to findings from different corners of the research field. We will discuss how specific exposures, such as shift work, long working hours, and social relations at work, might affect the risk of dementia in late life. Furthermore, we will present results on the relation of psychosocial strain experienced in midlife with cognitive decline and brain structural changes in later life. The four presentations emphasize different aspects of contemporary working life and together they provide state-of-the-art on the topic and serve as a platform for a discussion of the role of working conditions in relation to cognitive health in old age.
S2.1.1 An active job in midlife may prevent cognitive decline in later life
Aging Research Centre, Karolinska Institutet, Stockholm, Sweden
Aim: To examine whether job strain is associated with cognitive decline in old age, taking into account duration of exposure to job strain across life span. Methods: In a population-based cohort study, Swedish National Study on Aging and Care in Kungsholmen (SNAC-K), 2873 dementia-free participants aged ?60 years were followed-up for up to 9 years. Global cognitive function was measured by the Mini-Mental State Examination at baseline and all follow-up examinations. Occupational information over the whole working life was obtained by a structured interview. Job strain model was applied based on levels of job control and demands that were estimated through a validated psychosocial job-exposure matrix. Findings: In comparison with persons who had active job (high control and high demands), faster cognitive decline was shown in those who had low job strain (?: -0.14, 95% CI: -0.23 to -0.05), high job strain (?: -0.12, 95% CI: -0.22 to -0.02) and passive job (?: -0.23, 95% CI: -0.34 to -0.12), respectively. Moreover, compared with shorter durations, less cognitive decline was associated with longer duration of active job (1+ years) (?: 0.22, 95% CI: 0.15 to 0.29) and greater cognitive decline was associated with longer duration of low job strain (6+ years; ?: -0.10, 95% CI: -0.17 to -0.03), high job strain (5+ years; ?: -0.12, 95% CI: -0.20 to -0.03) and passive job (4+ years; ?: -0.13, 95% CI: -0.21 to -0.04). Conclusion: An active job may prevent cognitive decline in people aged 60+. Duration of exposure to job strain plays an important role in such associations.
S2.1.2 Association of psychosocial work stress with structural brain changes
Stress Research Institute, Stockholm University and Aging Research Centre, Karolinska Institutet, Stockholm, Sweden
Aim: To examine whether work-related stress is associated with structural brain changes in old age.
Methods: 440 dementia-free home-dwellers, aged 60+ years, who participated in a population-based cohort study, Swedish National Study on Aging and Care in Kungsholmen (SNAC-K) underwent brain magnetic resonance imaging scans at baseline and follow-ups during 6 years to assess regional brain volumes. Lifelong occupational data were collected through structured interviews. Levels of job control and demands were estimated through a validated psychosocial job-exposure matrix to generate four job-strain categories: high job strain, low job strain, passive job, or active job. Findings: Low levels of job demands were associated with smaller total hippocampal volume at baseline (?: -0.22, 95% CI: -0.38 to -0.06) compared with high levels. In comparison to people who had an active job, those who had a passive job had smaller total hippocampal volume (?: -0.28, 95% CI: -0.54 to -0.02). As compared to low job strain, high job strain was related to bigger hippocampal volume (?: 0.33, 95% CI: 0.09 to 0.58). No association between work stress and change of hippocampal volume was found over the 6-year follow-up. Conclusion: Psychosocial job strain may be associated with hippocampal volume cross-sectionally, but not longitudinally.
S2.1.3 Social relations at work and incident dementia
University of Copenhagen, Denmark
Aim: We investigated the association between social relations at work and incident dementia in old age. Methods: We analyzed data from two separate Danish cohorts consisting of 1,572 men in the first cohort and 6,436 men and women in the second cohort. In the first cohort, the participants reported whether they had possibilities to be in contact with co-workers, could get along with co-workers, and were satisfied with their supervisor. In the second cohort, the participants reported whether they had ever had a prolonged or serious conflict at work. The participants were followed up through registers for 29 and 23 years, respectively. We used Poisson regression to estimate Incidence Rate Ratios (IRR). Findings: After adjusting for potential confounders, only having limited contact with co-workers was associated with a higher risk of dementia (IRR=2.49, 95% CI 1.14-5.44). Conclusion: Our findings partially support the hypothesis of an effect of social relations at work on the risk of dementia.
S2.1.4 Shift work, long working hours, and dementia
University of Copenhagen, DenmarkAim: The aim was to investigate the effect of shift work and long working hours on the incidence of dementia in old age. Methods: We used data from two large cohorts. The first cohort comprised 4766 male employees from various workplaces in the Copenhagen area (baseline in 1970-1971), and the second cohort comprised 3082 male and female employees from the general working population in Denmark. Shift work and long working hours were self-reported and information about dementia diagnoses was obtained from registers. Findings: In the first cohort, we found no association between shift work/long working hours and dementia. In the second cohort, we found indications of an association between night work and dementia. In addition, participants with moderately increased weekly working hours had an increased risk of dementia. Conclusion: The organization of working hours might influence the risk of dementia, possibly through sleep deprivation, but the current knowledge is insufficient to support a causal relationship.