The majority of comparisons tended to highlight the commonalities in the PD phenotype between genders, particularly in reference to historical and early disease stage characteristics. However, gender may be an important factor related to the expression of PD features during the symptomatic disease course.

Asymmetric presentation of Parkinson disease features was a common occurrence in the clinical cohort. Asymmetry was reliably predicted by several clinical characteristics, although the moderate level of explained variance (i.e., between 16 and 23%) highlighted the need for additional research examining predictive models of asymmetric disease. Recommendations for the classification and measurement of asymmetric disease are discussed.

Two studies were designed to examine important predictors of pain following spinal cord injury (SCI), and the impact of pain on self-reported quality of life (QOL). Pain was defined as "interference in day-to-day activities secondary to pain". In order to determine risk factors associated with the development of pain interference, Study 1 examined the predictive validity of multiple demographic, medical, and QOL variables at year 1 post-SCI to self-reported pain interference 2 years post-injury. Results showed that middle age (30-59-year-olds), lower self-reported mental health, and pain interference at 1 year post-SCI were the most important unique predictors of pain interference 2 years post-SCI. In Study 2, participants were separated into four groups; (1) those pain-free at years 1 and 2, (2) those pain-free at year 1 and in pain at year 2, (3) those in pain at year 1 and pain-free at year 2, and (4) those in pain at years 1 and 2. Results showed that only those experiencing a change in pain interference status reported a change in QOL. More specifically, those developing pain interference (group 2) from year 1 to year 2 reported decreased life satisfaction, physical health, and mental health, whereas, those with resolving pain interference from year 1 to year 2 reported an increase in these same domains. Unexpectedly, change in pain interference status was unrelated to change in self-reported handicap. Implications and future directions are discussed.