High education, but not occupation or work experience, is related to a lower risk of dementia in the oldest‐old: The 90+ Study

Abstract

AbstractBackgroundMost studies find that high education, work experience, and cognitively demanding occupations are independently associated with a lower dementia risk, and that the association may be strongest for occupation. It is hypothesized that these three factors provide cognitive reserve. Here we examine the risk of dementia in relation to education, work experience, and occupation in the oldest‐old (age 90+), an age group with the highest dementia risk.MethodWe analyzed data on 598 participants of The 90+ Study, a longitudinal study of aging and dementia, who were previously part of the population‐based Leisure World Cohort study, had no dementia at entry into The 90+ Study, had additional follow‐up, and reported their education and occupation. Education was categorized as <high school, vocational school or some college, and >college. Occupation categories were assigned based on 1970 US Census and grouped according to cognitive demand: more (managers/administrators and professionals) and less (all other occupations). Participants who never worked/ housewives were a separate group. We estimated risk of dementia in relation to education, occupation, and having worked vs. never worked using Cox regression.ResultAt baseline, the average age was 93 years, 42% had ≥college education, and 52% had more cognitively demanding occupations (Tables 1, 2). Over an average of 3 years of follow‐up, 48% of participants developed dementia. Compared to participants with <high school education, those with >college education had a 32% lower risk of dementia (HR=0.68) in the unadjusted model and 35% lower risk when adjusted for occupation (HR=0.65). Adjustment for sex or for sex and occupation did not change the results (Table 3). Occupation (men and women) (Table 4), or having worked (women only) (Table 5), were not related to dementia risk.ConclusionIn this oldest‐old group, education, an early life experience, remains strongly associated with dementia risk. This is in contrast to other life‐long dementia risk factors, such as APOEe4, which are no longer associated with dementia risk at very advanced ages. These results suggest that education determines cognitive reserve and life‐long lifestyle factors that protect against dementia, whereas occupation or work experience do not contribute to cognitive reserve.