Is Occupational Complexity Associated With Cognitive Performance Later in Life?

Occupational complexity is associated with cognitive performance later in life in older adults, according to study findings published in the journal Alzheimer’s Disease & Dementia.

Current research suggests that cognitive decline may be deferred in individuals who have had intellectually stimulating activities in adulthood, such as complex work environments. However, most research has targeted cognition at a single point in time, which makes it difficult to ascertain a direct correlation, as a potential inverse relationship is also possible (i.e., higher mental ability influences occupational opportunities or complexity of work-related activity). Additionally, an evidence gap exists for racially and ethnically diverse populations, as most evidence is based primarily from European samples.

For the study, researchers aimed to evaluate occupational complexity and its interplay between late-life cognition function across a diverse cohort aged 65 years and older.

The Kaiser Healthy Aging and Diverse Life Experiences (KHANDLE) was set forth to examine the association between cognitive decline and life factors amongst a racially and diverse cohort. Occupational complexity and cognitive measures were obtained and analyzed within the cohort.  Exclusion criteria consisted of those who have a diagnosis of dementia or other neurodegenerative disease, or presence of any health condition that would affect study interviews. Those who did not report race or ethnicity or who were missing occupational information were also excluded from the study.

Individuals were surveyed on their “main life occupation” job title and assigned an occupation code. Occupational complexity scores were derived from the occupational code and assigned a specific code for 3 separate domains (ranging 0-6 for data; 0-8 for people; 0-7 for things). Complexity scores were derived from the Department of Transportation (DOT, 4th Edition). A higher score indicates a higher level of occupational complexity. Each individual was then assigned low, medium and high categories according to a turtle distribution of the pooled sample across each occupational complexity domain.

Cognition, based on 3 domains (executive function, verbal episodic memory, and semantic memory) were assessed using the Spanish and English Neuropsychological Assessment Scales (SENAS).

A total of 1,536 individuals participated in the final analytic sample (24% Asian, 27% Black, 20% Latino, 29% White). Statistical distribution across each occupational complexity by race and ethnicity were found significantly different.

Black and Latino individuals were categorized in the lowest complexity tertile for complexity with data (22% Asian, 37% Black, 39% Latino, and 26% White) and for complexity with people (24% Asian, 33% Black, 33% Latino, and 25% White). Asian individuals were found to be disproportionately categorized in the lowest complexity tertile for complexity with things (32% Asian, 28% Black, 28% Latino, 29% White).

Middle and highest tertiles of occupational complexity with data was associated with a higher baseline executive function (β=0.14; 95% CI, 0.03-0.24 and β = 0.11; 95% CI, 0.00-0.22, respectively), as well as slower rates of decline (β=0.06; 95% CI, 0.03-0.08 and β= 0.03; 95% CI, 0.01-0.06, respectively).

The highest tertile of occupational complexity with people was associated with a higher baseline verbal episodic memory (β= 0.12; 95% CI, 0.00-0.24), but not associated with decline. A higher baseline semantic memory was associated with the middle and highest tertiles of occupational complexity with people (β= 0.15; 95% CI, 0.05-0.25 and β= 0.23; 95% CI, 0.12-0.34, respectively), but not associated with decline. 

A statistically significant interaction was found between occupational complexity with things and race to semantic memory, such that individuals in the highest tertile (vs lowest), Asian individuals (vs White) have a lower baseline semantic memory (β= −0.27; 95% CI, −0.53 to −0.008), but not for verbal episodic memory or executive function. In stratifying for race and ethnicity, however, no statistically significant findings were seen in relationship to occupational complexity with things.

Study limitations included assigning occupational complexity according to the DOT, which may not account for individual variability within the same occupational title.

The researchers noted, “Higher occupational complexity with people was associated with higher baseline cognition across all domains.” They conclude “we found that higher occupational complexity with data and people were associated with different cognitive domains in this racially and ethnically diverse longitudinal cohort of older adults.”