Is Complexity of Work Associated with Risk of Dementia?: The Canadian Study of Health and Aging

Abstract

The authors evaluated the association of complexity of work with data, people, and things with the incidence of dementia, Alzheimer's disease, and vascular dementia in the Canadian Study of Health and Aging, while adjusting for work-related physical activity. The Canadian Study of Health and Aging is a 10-year population study, from 1991 to 2001, of a representative sample of persons aged 65 years or older. Lifetime job history allowed application of complexity scores and classification of work-related physical activity. Analyses included 3,557 subjects, of whom 400 were incident dementia cases, including 299 with Alzheimer's disease and 93 with vascular dementia. In fully adjusted Cox regression models, high complexity of work with people or things reduced risk of dementia (hazard ratios were 0.66 (95% confidence interval: 0.44, 0.98) and 0.72 (95% confidence interval: 0.52, 0.99), respectively) but not Alzheimer's disease. For vascular dementia, hazard ratios were 0.36 (95% confidence interval: 0.15, 0.90) for high complexity of work with people and 0.50 (95% confidence interval: 0.25, 1.00) for high complexity of work with things. Subgroup analyses according to median duration (23 years) of principal occupation showed that associations with complexity varied according to duration of employment. High complexity of work appears to be associated with risk of dementia, but effects may vary according to subtype.

Education, Occupation, and Dementia: The Bavarian School Sisters Study

“…Numerous studies found that cognitive activity is associated with a lower risk of dementia even in old age [32][33][34] , and complex intellectually demanding work may have a protective effect [35,36,37] . On the other hand, a number of studies have demonstrated that developmental markers, including height [38,39] , limb length [40] , and head circumference or total intracranial volume as measures of pre-morbid brain size, are related to cognitive impairment and dementia in late life [41] .…”

The Relation of Obesity to Performance in Verbal Abilities, Processing Speed, and Cognitive Flexibility in Old Age: The Role of Cognitive Reserve

“…This view is supported by findings that engaging in a variety of leisure activities and pursuing an occupation with a high cognitive level lead to enrichment effects, make a contribution to cognitive reserve throughout a person's lifetime, and are related to better cognitive functioning (i.e. better processing speed, memory, and executive functioning) in old age [4,10,11,12,13] (see [14] for a review on enrichment effects in adulthood; see [15] for a recent meta-analysis).…”

Physical fitness, physical activity, exercise training and cognitive function in older adults

“…There are a few studies that examined the relationship between cognitive function and work-related physical activity. Kröger et al (2008) fo-cused on work complexity in a 10-year population study with the Canadian Study of Health and Aging 44) which revealed that highly complex work with people or things gave the participant a 28 -64% reduced risk of dementia. In a study on the elderly in Sydney, Australia, Suo et al (2012) found that higher total lifetime experiences are linked with increased grey matter volume in the hippocampus, and supervisory and managerial experience in midlife was the dominant contributor to this effect.…”