Background: It has previously been speculated that a distinct premorbid personality characterized by introversion, rigidity, and over cautiousness might be associated with Parkinson disease (PD). Only 1 previous study has assessed personality before PD onset, and other data collected retrospectively do not exclude reverse causation.
Objective: We relied on the longest held job reported in an interview to infer personality traits and motor skills for 355 incident PD patients and 335 population controls enrolled in a PD study in California.
Methods: Jobs were coded according to the 1980 US Census Occupational Code and assigned scores for various demands, skills, and aptitudes required by the job.
Results: None of the occupational temperament or interest factors required, expected, or exhibited by workers were related to statistically significantly higher odds of having PD per unit increase in scores, whereas there was some suggestion of differences when the extremes were examined. Analyses of physical aptitude factors showed that PD cases were less likely to have worked in jobs that involved certain motor skills.
Conclusions: This study uses a novel approach to assess personality traits using occupational characteristics. Most job attributes thought to reflect conservativeness; risk taking, stress resistance, and flexibility were not associated with PD in a linear manner. Thus, these occupation-derived traits do not seem to support the existence of a distinct parkinsonian personality. However, the negative associations with jobs requiring certain motor skills are intriguing, and may suggest very early premotor features or a lack of continuous motor training as a risk factor for PD.
Departments of *Epidemiology
§Environmental Health Sciences
†Neurology, University of California
‡Department of Psychology, University of Southern California, Los Angeles, CA
Supported by grants T32ES01545, ES10544, U54ES12078, and 5P30ES07048 from the NIEHS, NS038367 from the NINDS, PC051037 from the DOD, and funding from the Michael J. Fox Foundation.
Disclosures: None for all authors.
Reprints: Beate Ritz, MD, PhD, Department of Epidemiology, Environmental Health Sciences and Neurology, UCLA, Schools of Public Health and Medicine, BOX 951772, 650 Charles E. Young Drive, Los Angeles, CA 90095-1772 (e-mail: firstname.lastname@example.org).
Received April 6, 2010
Accepted March 3, 2011