Jake Moskowitz | Natural Sciences March 2014 | Page 38 Journal for Undergraduate Research Opportunities |© March 2014| Page 38 Occupational Complexity as a Predictor of Cognitive Reserve Jake Moskowitz and L. Stephen Miller*, Ph.D., Department of Psychology and Bio-Imaging Research Center *In collaboration with Nicolas Puente, M.S., Fayeza Ahmed, Ph.D. (VA Puget Sound, Seattle, WA), Carlos Faraco, Ph.D. (Vanderbilt University Medical Center, Nashville, TN), Courtney Brown, Ph.D., Sarah Evans, and Kristie Chu. ABSTRACT. The concept of cognitive reserve suggests that certain individuals possess built-up mechanisms that enable them to cope with the onset of degenerative neurological diseases better than others. This “reserve” of cognitive function is thought to be derived from a variety of demographic factors, including but not limited to occupational and educational attainment, income, literacy, and age. The Wechsler Test of Adult Reading (WTAR) has proven to be a valid proxy for cognitive reserve in older adults, successfully predicting premorbid IQ in patients with minimal to mild Alzheimer’s disease. WTAR scores have been shown to be heavily predicted by several demographic variables, including education, occupation, age, gender, race, and region of residence. The relative importance of occupational data to predicting WTAR scores, however, remains a point of some disagreement among researchers. This study seeks to determine the significance of occupational complexity toward predicting the WTAR values of a community-based older-adult population. Demographic data containing educational and occupational attainment, age, and gender were compared against participants’ WTAR scores. When analyzed using a hierarchical regression model, occupational complexity was found to significantly predict WTAR scores, even when education, gender, and age were controlled for. This finding supports the notion that long-term occupational complexity contributes to cognitive reserve throughout one’s life. While further research is needed, this link between occupation and cognitive reserve could contain valuable implications for the public health struggle against the rising global epidemic of neurological degenerative disorders such as Alzheimer’s disease. Introduction “Cognitive reserve” is a working theory designed to explain the repeated finding that brain disease pathology is not directly correlated with clinical symptomatic manifestation of that disease. An example of this phenomenon is illustrated by Katzman et al. (1988), who performed cognitive testing and postmortem examination on 137 elderly nursing facility residents. Seventy-eight percent of the participants were clinically demented, while 55% possessed Alzheimer’s disease brain pathology. Yet it was found that ten residents who scored in the upper quintile of the healthy population scores had the characteristic brain pathology of mild Alzheimer’s disease. Neocortical plaque counts of these ten patients accounted for 80% of those patients labeled as demented with Alzheimer’s. A more recent study reveals an older adult population showing signs of amyloid deposition, an early marker of Alzheimer’s disease, that scored significantly better on cognitive assessment tests when compared to a cognitively normal control population (Aizenstein et al., 2008). In order to explain this confounding discrepancy between disease pathology and clinical disease manifestation, the cognitive reserve model posits that there exist certain individuals who have, either through genetic or environmental causes, developed a compensatory barrier, either through active or passive means, between their disease pathology and their real- life cognitive performance. Defined quantitatively, cognitive reserve is the amount of brain damage that an individual can sustain before reaching their threshold for clinical expression (Stern, 2002). Once this threshold is reached, however, the theory holds that these “cognitive reserve” individuals will then experience a much faster rate of cognitive decline than individuals with less reserve due to the existing accumulation of advanced disease pathology that these individuals possess (Fritsch et al., 2002; Meng and D’Arcy, 2012; Stern et al., 1999; Wilson et al., 2004). Cognitive reserve is thought to be determined by a variety of demographic factors, including but not limited to occupational and educational attainment, income, literacy, gender, and age. Of these factors, level of education has been the most comprehensively studied to date among multiple diverse populations (Meng and D’Arcy, 2012). Though predicted effects of education vary by study (Fritsch et al., 2002; Le Carret et al., 2005; Stern et al., 1999; Wilson et al., 2004), a recently published meta-analysis of 69 quantitative studies, all published between 1980 and 2011, provides robust evidence of a negative relationship between level of education and incidence and prevalence of dementia. This quantitative meta-analysis consistently shows that individuals with lower levels of education have a greater overall risk of dementia, including both Alzheimer’s disease and vascular dementia (Meng and D’Arcy, 2012). Other studies have shown that higher levels of