"Complexity of work and risk of Alzheimer's disease: a population-based study of Swedish twins"
We examined the association between risk of dementia or Alzheimer's disease (AD) and occupation by using measures of complexity of work with data, people, and things. The study included 10,079 members of the population-based Swedish Twin Registry who were participants in the HARMONY study. We diagnosed dementia by means of a two-stage procedure--cognitive impairment screening followed by full clinical evaluation. We analyzed data with case-control and cotwin control designs. The cotwin control design provides control over genetic and familial factors. In the case-control study, controlling for age, gender, and level of education, we found that more complex work with people was associated with reduced risk of AD. Greater complexity of work with people and data was protective in twin pairs discordant for AD. Findings suggest that greater complexity of work, and particularly complex work with people, may reduce the risk of AD.
Occupation may be particularly interesting with respect to examining the potential association between intellectual stimulation and subsequent dementia, because people generally spend a substantial portion of their adult years at work. Along the lines of the use it or lose it hypothesis (Katzman, 1995; Orrell & Sahakian, 1995), occupations with high mental demands may provide a form of mental exercise that supports brain function further into older adulthood. Mental exercise provided by frequent engagement in intellectually demanding activity at work may facilitate the maintenance of inherent cognitive reserve, leading to more sophisticated cerebral networks in old age (Churchill et al., 2002; Kolb & Whishaw, 1998) and allowing aging individuals to tolerate dementia neuropathology longer into the progression of the disease (Scarmeas & Stern, 2003; Stern et al., 1995). A similar hypothesis was articulated by Schooler (1984) to explain the effect of complexity of work on cognitive functioning in nondemented older adults. Schooler posited that complex environments that reward cognitive effort and require making decisions motivate individuals to continue to develop their intellectual capacities. To substantiate the environmental complexity hypothesis, Kohn and Schooler (1983) and Schooler, Mulatu, and Oates (1999) derived a factor score from self-reports about complexity of work with data, people, and things, modeled after the Dictionary of Occupational Titles (U.S. Department of Labor, 1965). Results based on this measure suggested that substantive complexity of work facilitates intellectual flexibility and promotes stable cognitive function. (p.251)
KeywordsAgeing, Older Workers, Retirement, Complex Work, Mental Development, Psychological Functioning, Dementia, Cognitive Impairments
ThemesPsychological Centrality of Work
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