"Is complexity of work associated with risk of dementia? The Canadian Study of Health And Aging"
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.
Maintenance of cognitive reserve (43, 44) by mental stimulation may be an underlying mechanism explaining the relation of higher complexity of work with people and things to lower risk of dementia found in our study. According to this hypothesis, intellectually demanding activities at work may provide a type of exercise contributing to more sophisticated cerebral networks in old age (45, 46) or make it possible to tolerate dementia neuropathology for a longer period during disease progression (7, 14). A study by Stern et al. (14) tested work complexity within the concept of cognitive reserve by using factor scores reflecting substantive complexity, interpersonal demands, management requirements, and physical demands. Patients who held jobs involving high interpersonal and physical demands had relatively greater deficits in cerebral blood flow in the parietal area when compared with patients who held low-demand jobs. These results may indicate a delay in clinical expression of Alzheimer’s disease attributable to the protective effect of occupational demands on the brain. (p.828)
KeywordsDementia, Cognitive Decline, Cognitive Function, Metal Development, Stress, Work Stress, Health Risk
ThemesPsychological Centrality of Work
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