The cognitive reserve’s effects modified by genetics. A research on Alzheimer’s disease and psychological problems.

Intro Do education and occupation relate to the prevalence of Alzheimer’s Disease (AD) / psychological problems (PP) and is there an interaction effect between the AD/Neuroticism polygenic score and education/occupation? Societal- and healthcare costs for AD and PP currently account for profound budget spending. Total projected cumulative healthcare costs and unpaid caregiving for AD, in the USA between 2017-2030, account for $3.2 trillion respectively $4.5 trillion. Total mental healthcare costs in the European Union, in 2010, accounted for $1,06 trillion. These costs are expected to double in 2030. Nearly 2 billion people suffer from PP every year. Well known is that education and a cognitive (un)stimulating job are associated with one’s risk profile for AD/PP. this mechanism is likely explained by the cognitive reserve hypothesis, a hypothetical reserve in the brain which is created by stimulating cognitive activities like education and one’s occupation. Data & Methods In this study we have access to the so-called polygenic risk score (PGS). This is a weighted score of genes relating to AD/PP. For AD we use the PGS for AD, for PP we use the PGS of neuroticism (N). Neuroticism is the tendency in individuals to experience negative emotions/being emotionally instable which makes them easily nervous or upset. We examine the relationship of the cognitive reserve controlling for genetics. More interestingly we examine if there exists an interaction effect between the cognitive reserve and genetics. Does the cognitive reserve have a different effect for people with different PGSs? We will support the results with a transformed Grossman Model, where, controlling for genetics, you can invest in the cognitive reserve and individuals experience (natural) depreciation of the cognitive reserve stock. When the cognitive reserve falls below a certain threshold, the individual is classified as having AD or PP. One of our main contributions is that we created a unique occupational index recoded from the 2000 United States Census, the International Standard Classification of Occupations (ISCO-08) and the Occupational Information Network (O*NET). Our study population consists of American white people who are 50 years and over. We obtain interaction effects through the linear probability model (LPM) and control these models with logistic regressions and marginal effects. Results For AD we find no evidence of existing interaction effects. For PP we find moderate evidence suggesting there could exist an interaction between white collar and the PGS for N. We do find for AD that education relates to the development of the disease. More years of education lowers the probability of developing AD, occupational measures are found to be insignificant related. For PP we only found a significant relation for occupation, where being white collar lowers the probability of developing PP, white collar is partly explained by education due to the correlation between the two variables. Education, alone, appeared to have no effect. Conclusion We found that cognitive reserve measures relate to AD/PP even when controlling for genetics. For PP we even found suggestive evidence of a possible interaction between being white collar and the PGS of N. This interaction effect should be examined more in depth.