TORONTO—High levels of occupational complexity, specifically related to work with people, enable individuals to maintain normal cognition despite white matter pathology in the brain, according to research described at the Alzheimer’s Association International Conference. The results “could have potential implications for preventing or maybe delaying Alzheimer’s disease onset in the future,” said Elizabeth Boots, research specialist at Wisconsin Alzheimer’s Disease Research Center in Madison.
Elizabeth Boots
According to one estimate, about 30% of cognitively healthy elderly adults may have widespread Alzheimer’s disease pathology. Cognitive reserve may allow these individuals to perform at a normal level of cognition despite this pathology. Because many people spend the majority of their lives at work, Ms. Boots and colleagues chose to examine occupational complexity as a measure of cognitive reserve. The investigators also focused on white matter hyperintensities, which increase the risk for cognitive decline and are common in Alzheimer’s disease. “The objective of our study was to determine whether occupational complexity is associated with more white matter hyperintensities when participants are matched for cognitive function, which would support the cognitive reserve hypothesis,” said Ms. Boots.
Examining Cognitive Testing and Imaging
She and her colleagues, led by senior author Ozioma Okonkwo, PhD, Assistant Professor of Geriatrics at the University of Wisconsin School of Medicine in Madison, selected 284 participants in the Wisconsin Registry for Alzheimer’s Prevention, a group of approximately 1,500 cognitively healthy people with increased risk for Alzheimer’s disease because of parental family history. Participants underwent extensive cognitive testing, and the researchers looked at the average of four cognitive domains—verbal learning and memory, immediate memory, working memory, and speed and flexibility—to match individuals on cognitive function. Participants also underwent a brain scan for white matter hyperintensities.
In addition, study participants described as many as three occupations that they had performed, including the number of years spent on each occupation. Ms. Boots and her colleagues rated each job for three categories of occupational complexity (ie, complexity of work with data, people, and things). In the domain of work with people, for example, the researchers considered taking instructions as the least complex occupation, and mentoring the most complex. They weighted the scores by the number of years on the job and summed the scores to create a total occupational complexity measure.
Social Interaction May Be Crucial
Average age in the study cohort was 60, and 67% of participants were female. Study participants had an average of 16.67 years of education. When the investigators controlled the data for cognitive function, they found that higher levels of occupational complexity were associated with increased white matter hyperintensities in the brain. “Those with higher levels of occupational complexity are able to tolerate more white matter pathology in the brain and still perform at the same cognitive level as their peers,” said Ms. Boots. The association did not change when the researchers controlled for potential confounders such as education, socioeconomic status, and vascular risk. Furthermore, Ms. Boots and colleagues found that complexity of work with people, but not complexity of work with data or things, had the greatest effect on preserving cognitive performance.
The results support the cognitive reserve hypothesis and suggest that social interaction plays a unique role in cognitive reserve, according to Dr. Okonkwo. “These analyses underscore the importance of social engagement in the work setting for building resilience to Alzheimer’s disease,” he added. The Alzheimer’s Association, the NIH, and the Extendicare Foundation funded the study.
Suggested Reading
Boots EA, Schultz SA, Almeida RP, et al. Occupational complexity and cognitive reserve in a middle-aged cohort at risk for Alzheimer’s disease. Arch Clin Neuropsychol. 2015;30(7):634-642.
Lo RY, Jagust WJ; Alzheimer’s Disease Neuroimaging Initiative. Effect of cognitive reserve markers on Alzheimer pathologic progression. Alzheimer Dis Assoc Disord. 2013;27(4):343-350.
Pool LR, Weuve J, Wilson RS, et al. Occupational cognitive requirements and late-life cognitive aging. Neurology. 2016;86(15):1386-1392.
Stern Y. Cognitive reserve in ageing and Alzheimer’s disease. Lancet Neurol. 2012; 11(11):1006-1012.