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The purpose of this study was to develop and psychometrically test the Activity Effort Scale among women aging with the affects of paralytic polio. On the basis of prior qualitative research, six items were generated. Two researchers with expertise in disability were consulted for examination of the items, which led to the addition of two more items to the scale. Next, a survey was sent to 500 women with a history of paralytic polio. Data from participants were subjected to psychometric testing: factor analysis, reliability testing, and correlation with existing measures. Useable surveys were returned by 299 women aged 49 to 75 years. Mean age of infection with polio was 7.6 years, and 54% had spinal polio. Principal component analysis of the 8-item scale resulted in one component with an eigenvalue above 1, explaining 74% of the variance. The Cronbach's alpha was .92. Correlations between variables supported content validity. Data suggest that the Activity Effort Scale is a valid and reliable tool consisting of one component measuring frequency of effort exerted beyond levels of discomfort, pain, and fatigue among women aging with paralytic polio.
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Aging with the effects of paralytic polio is arguably an exemplar for the experience of aging with disability from an early age (Alexander, 1990). It has been hypothesized that aging with a disability from an early age is conceptually different than aging into a disability in later life. The impact of functional limitation on socialization, education, and overall role acquisition is often age related; therefore, the timing of functional limitations influences how it is interpreted by the individual and by the society (Verbrugge & Yang, 2002). Further, the longer one lives with a disabling condition, the more likely he or she will develop comorbidities (Jans & Stoddard, 1999). Women with paralytic polio have aged with various impairments and functional limitations that may include muscle paralysis leading to the inability to breathe without ventilator assistance or paralysis of extremities leading to the inability to walk or hold items with their arms (Koh, Williams, & Povlsen, 2002). Over time, women aging with paralytic polio, when compared with women in general, may be at higher risk for osteoporosis (Schrager, 2004), asthma, and hypertension (Campbell, Sheets, & Strong, 1999; Harrison & Stuifbergen, 2001). On average, the current polio survivors have been aging with varying degrees of functional limitations since the end of the polio epidemics, the 1950s to the early 1960s, and are at risk for developing comorbid conditions and an associated poorer quality of life (Harrison & Stuifbergen, 2001; McNaughton & McPherson, 2003).
As polio survivors have aged with early-onset impairment, many have also experienced new-onset fatigue, pain, and weakness in previously impaired muscles, which is called postpolio syndrome (PPS). Age-related changes experienced by polio survivors after years of living with a stable impairment have a multitude of effects on their lives (Harrison, 2004; Maynard, 1995; McNaughton & McPherson, 2003). Persons aging with polio have reported higher levels of depressive symptoms when compared with nondisabled age-matched controls (Kemp & Krause, 1999). Moreover, those who experienced pain, weakness, and fatigue have reported less satisfaction with their lives (Burger & Marincek, 2000) and a poorer quality of life (Kling, Persson, & Gardulf, 2000) than did those without pain, weakness, and fatigue. This may be because impairments that occur with increasing age hinder the ability to socially integrate (Farbu, Rekand, Aarli, & Gilhus, 2001).
In previous studies of polio survivors (Harrison & Stuifbergen, 2001, 2006), it was theorized that levels of comorbidity could be explained using the combined disablement (Verbrugge & Jette, 1994) and allostatic load (McEwen & Steller, 1993) models. In other words, the cumulative stress of living with a functional limitation increased susceptibility to illness over time. The combined models helped explain the increased levels of comorbidity, but the link between disablement and increased allostatic load needed further clarification. Albeit the link was thought to be the result of increased barriers to health, it was not conceptually clear. The mechanism for how disablement increased a person's allostatic load and their subsequent risk for comorbid conditions needed further work. From a previous qualitative study (Harrison, 2006) and a review of the extant literature, the frequency of "activity effort" is now theorized to be the necessary conceptual link between the two models that explains the increased comorbidity over time.
The purpose of this article was to introduce the concept of activity effort and the evidence in support of a newly developed questionnaire to measure the concept, the Activity Effort Scale. The allostatic load and the disablement process models are reviewed briefly as is the concept of activity effort. Next, the results of a study measuring the psychometric properties of the Activity Effort Scale among women with polio are presented and discussed.
Allostatic load is used to conceptualize the impact of living with high levels of biological stress with resultant wear and tear on the body (Seeman, McEwen, Rowe, & Singer, 2001). When people are able to adapt to challenges without developing high levels of physiological stress, they reach allostasis (Sterling & Eyer, 1988). When people live with high levels of stress over the life course but are not able to adapt, physiological damage occurs resulting in illness due to the long-term activation of neurohumoral mechanism meant only for short-term compensation (McEwen & Stellar, 1993). Biological markers have been proposed to measure allostatic load through physiological measurement of the body's function, which include measures of the "hypothalamic--pituitary--adrenal axis, sympathetic nervous system, cardiovascular system, and metabolic processes" (Seeman et al., 2001, p. 4770). Physiological measures have included various biomarkers such as cortisol levels, C-reactive protein, fibrinogen, creatinine clearance, epinephrine, homocysteine, blood pressure, dopamine, waist-to-hip ratio, and fasting glucose levels (Szanton, Gill, & Allen, 2005). The levels of allostatic load are calculated by "using a data driven partitioning of the sample" (Seeman et al., 2001, p. 4771). In other words, people are stratified based upon their relative risk by summing the number of measures that the individual scored at the top quartile or perhaps top 10% of risk (Szanton et al., 2005).
High levels of allostatic load have been associated with worse mortality, functional limitations, and mental health outcomes in primarily older populations (Gruenewalk, Seeman, Ryff, Karlamangla, & Singer, 2006; Seeman et al., 2001; Seplaki, Goldman, Weinstein, & Lin, 2004). In a population-based study of 2000 Taiwanese middle-aged and elderly people, measures of cortisol, epinephrine, noreprinephrine, dopamine, dehydroepiandrosterone sulfate (DHEA-S), growth hormone, immune system factors, blood pressure, cholesterol, glucose, and weight were compared based upon degree of functional limitations. Those people who were substantially impaired had significantly higher levels of cortisol, DHEA-S, and interleukin-6 than those of people who had no impairment. In addition, those who were substantially impaired had higher blood pressure, cholesterol, triglycerides, fasting glucose, and glycosylated hemoglobin. The authors asserted that there is an association between "profiles of functioning and physiological parameters of the stress response" (Seplaki et al., 2004, p. 210). Evidence also suggests that physiological adaptation to stress may be affected by early-life experiences, such as childhood trauma, which may lead to lasting and exaggerated stress responses (McEwen, 2003).
The disablement process model theorizes that disablement is due to the progression from pathology to impairment, from impairment to functional limitation, and from functional limitation to disability (Verbrugge & Jette, 1994). For instance, a woman with a history of pathology due to a poliomyelitis infection may have an impaired nerve that no longer innervates her leg muscles and subsequently be unable to move her legs due to that impairment. If the woman with the pathology, impairment, and functional limitation, for example, paralyzed legs, is unable to perform expected social roles such as work, marriage, or volunteering, she may be characterized as disabled. Being disabled, however, is not exclusively a result of the pathology, impairment, and/or functional limitation. Internal and external factors may influence her ability to maintain her social roles. For instance, if she uses a wheelchair and has access to ramps, she can continue to go to her place of employment. Of particular interest in this research is the relationship between the concepts of functional limitations and disability. These two concepts are reviewed below.
For women with polio, functional limitation is a result of impairment of nerves with subsequent muscle paralysis as a direct result of the pathological changes associated with poliomyelitis. Typically, polio survivors experienced initial paralysis then improved function during the first 10 to 20 years postinfection followed by a second decline 20 years later (Wenneberg & Ahlstrom, 2000). The most common type of decline includes muscle weakness, fatigue, and pain in previously affected muscles in PPS. In a study of 120 polio survivors, muscle deterioration was present in the flexor muscles of ankle, hip, and knee, and it was experienced at a rate greater than expected with normal aging (Klein, Whyte, Keenan, Esquenazi, & Polansky, 2000). In a study of 27 polio survivors, the rate of muscle decline averaged 1% per year. Their muscles showed evidence of chronic and new loss of neurons, with a slow disintegration of terminal nerve axons (Dalakas et al., 1986). This translated into a functional decline because many lost the ability to perform the physical activities they previously performed during the first 10 to 20 years after rehabilitation. In a study of 103 polio survivors, Nollet et al. (2001) reported that current functional limitations included problems with walking outside (46%) and climbing stairs (41%; Nollet et al., 2001).
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