Quality of Life and Life Satisfaction as Related to Tremor, Motor, and Cognitive Symptom Profiles in Adult Residents Exposed to Manganese: A Dissertation

This study examined the impact of motor and cognitive symptom profiles on health-related quality of life and life satisfaction in community-dwelling adults who have been exposed to environmental manganese (Mn) through industrial pollution. Manganese (Mn) is a naturally-occurring element that is essential for normal functioning and is found in the body in small amounts. Mn is neurotoxic; excessive exposure is associated with parkinsonian-like motor and tremor symptoms and adverse cognitive effects, including problems with executive functioning (EF), similar to those found in the later stages of Parkinson's disease (PD). Although the two disease processes have important differences, Mn neurotoxicity has a similar clinical presentation and pathophysiology as does PD. However, there is significant heterogeneity in the clinical presentation of both Mn neurotoxicity and PD, as individuals with both diagnoses vary in the presence and/or severity of motor, tremor and cognitive symptoms.;Studies seeking to differentiate PD patients into subgroups with associated outcomes based on motor and tremor symptoms using cluster analysis have identified tremor-dominant (TD) and non-tremor dominant (NTD). NTD PD presents without tremor but with symptoms including bradykinesia, rigidity, postural instability and gait disturbance, and is also associated with impairment in EF and lower quality of life. Currently, MRI studies are in the beginning stages of identifying a typical course of pathophysiology in the Mn-exposed brain, and it is unclear whether differing patterns of pathophysiology, symptoms and associated impairment exist in Mn neurotoxicity, as they do in PD.;Using cluster analysis, TD and NTD symptom clusters were identified, as hypothesized. Two additional clusters were identified: Executive Dysfunction and Normal Functioning. The residents in the NTD cluster did not have impairment in EF, as hypothesized. Instead, residents with impairment in EF formed their own cluster. Residents in the NTD and Executive Dysfunction clusters resembled one another qualitatively on levels of quality of life, life satisfaction, and positive symptom distress. These findings suggest NTD and executive dysfunction symptoms in Mn-exposed individuals should be a focus of clinical attention. Furthermore, results indicate neuropsychological evaluations will add to the knowledge of negative health effects from Mn and assist in planning appropriate treatment programs.