Date

May 2008

Document Type

Dissertation

Degree Name

Ph.D.

Institution

Oregon Health & Science University

Abstract

Background: Fibromyalgia (FM), a debilitating multi-symptom disorder, affects nearly 10 million Americans, with an annual direct cost of over $20 billion per year. As our population continues to age, it is expected that those 65 years of age and older will grow to 70 million people by 2050. Considering approximately 9% of older adults have FM, this syndrome poses a serious health concern. Mechanisms underlying FM are rapidly emerging, yet a single, unifying physiologic framework continues to elude researchers. Therefore treatment relies largely on managing symptoms and promoting physical function. Poor physical function in older adults with FM poses serious limiting effects, and is correlated with greater risk for disability and increased financial burden that ultimately places older adults at risk for loss of independence. Comprehensive symptom management interventions are proposed to be the most effective approach to preventing or minimizing poor physical function for those with FM. However, there is limited study of the relationship between the multiple symptoms of FM and physical function in FM, especially specific to older adults. This gap may impede the development of multi-modal interventions that include appropriate symptom management, aimed to prevent poor physical function. Objectives: The purpose of this study was to describe symptoms in adults with FM, determine the relationship between symptoms and physical function, and assess the moderating effect of comorbidity and age on this relationship. Design: This study was a cross-sectional descriptive correlational study. The specific aims of the study were: to describe a comprehensive set of symptoms in terms of the frequency, severity, and distress; to examine which symptoms best predict perceived physical function; and to examine the relationship between co-morbidity, age, symptoms, and perceived physical function. Methods: Adults over the age of 50 were randomly identified from the Oregon Health & Science University FM patient database. Questionnaires were mailed including an investigator-developed 29-item Likert scale for FM specific symptoms. Individual symptom domains were elicited: frequency (1-4), severity (1-4), and distress (0-4), with higher numbers indicating greater symptom burden, and a composite symptom score (2-12) was calculated using all 3 symptom domains. Additionally, responders completed the Late-Life Function & Disability Instrument: Function Component (LLFDI), a wellvalidated instrument in which 0-100 scaled scores indicate physical function categories ranging from no functional limitation (>76) to severe functional limitation (<42), and the Charlson Comorbidity Index, a weighted index with scores ranging between 0 to 41. Analysis: Descriptive statistics were used to characterize demographic and clinical variables. Frequencies and plots were used to describe the frequency, severity, and distress of each symptom experienced within the sample. Hierarchical regression modeling was used to examine influence of each symptom on physical function while controlling for pain. Correlation between each symptom and perceived physical function were evaluated for entering symptoms in the regression analysis. The final regression included all chosen symptoms entered simultaneously to determine the effects of each symptom on perceived physical function controlling for all other symptoms. The moderating effect of age and co-morbidity on the relationship between symptoms and physical function was evaluated in additional regression analyses. Results: The sample reported experiencing an average of 20 symptoms in the previous seven days. The rank-order for the dimensions of frequency, severity, and distress differed for each symptom. The symptoms most reported by the sample were pain, stiffness, fatigue, non-refreshing sleep, forgetfulness, difficulty staying asleep, and muscle spasms. Symptom composite correlations of the 29 symptoms with perceived physical function revealed significant findings of weak to moderate correlations for fifteen symptoms. The regression model determined that pain, anxiety, fatigue, stiffness, and dizziness accounted for 37% of the variance in perceived physical function. Although a significant difference in the number of symptoms was present between the middle-aged and older-aged groups, age was not correlated with perceived physical function, and therefore did not have a moderating effect on the relationship between symptoms and perceived physical function. Comorbidity did have a significant correlation with perceived physical function, but further analysis revealed no moderating effect for comorbidity. Conclusions: This study yielded five novel findings: 1) the total sample reported a very high number of symptoms, with the middle-aged group reporting significantly more symptoms than the older-aged group; 2) the distress dimension yielded a markedly different rank-order than the frequency and severity dimensions: the most distressing symptom was fear of symptoms worsening while the most frequent symptoms were pain, fatigue, sleep-related symptoms, and stiffness, and the most severe symptoms were also sleep-related symptoms and fatigue; 3) five symptoms were identified that account for 37% of the variance in physical function: pain, fatigue, anxiety, stiffness, and dizziness; 4) no difference existed between the two age groups on perceived physical function, and 5) while age was not correlated with physical function, comorbidity significantly correlated with physical function and accounts for 6.8% of the variance in perceived physical function; neither age nor comorbidity have a moderating effect on the relationship between symptoms and perceived physical function. Further research is needed to replicate the study in a larger sample consisting exclusively of older adults, and to confirm the self-report findings of perceived physical function with objective measures of physical function.

Identifier

doi:10.6083/M4VT1Q2T

School

School of Nursing

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