Occupational characteristics and cognitive performance among elderly male twins

To examine the effect of occupational characteristics on cognitive status change in members of the NAS-NRC Twins Registry of World War II veterans. Participants completed the modified Telephone Interview for Cognitive Status (TICS-m) on three occasions spanning a period of approximately 7 years. Based on factor analysis, occupational characteristics were interpreted as reflecting general intellectual demands (GI), human interaction and communication (HC), physical exertion (PE), and visual attention (VA). Based on regression analysis of TICS-m change that was dependent on twin pairing and additionally covarying for education, age at each testing event, medical conditions, and initial TICS-m score, higher GI was associated with a modest longitudinal improvement in TICS-m performance, whereas higher PE and VA were both associated with a modest decline. Subsequent analysis revealed that these significant effects were present among dizygotic twins, but not among monozygotic twins. Previous findings of a relationship between occupational characteristics and cognitive performance in later life may be partially explained by genetic factors; however, until these genes are identified, occupational characteristics may be useful markers.