Associations between illness perceptions and health-related quality of life in adults with cystic fibrosis

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Abstract

Objective

The objective of this work was to examine the relationship between illness perception, health status, and health-related quality of life (HRQOL) in a cohort of adults with cystic fibrosis (CF).

Methods

In the Project on Adult Care in Cystic Fibrosis, we administered five subscales (Illness Consequences, Illness Coherence, Illness Timeline—Cyclical, Personal Control, and Treatment Control) of the Illness Perception Questionnaire—Revised (IPQ-R). Multivariable linear regression analyses explored the associations between illness perception, health status, symptom burden, and physical and psychosocial HRQOL, as measured by various domains of the Cystic Fibrosis Questionnaire—Revised (CFQ-R).

Results

Among the 199 respondents (63% female; mean age, 36.8±10.2 years), IPQ-R scores did not differ on age, gender, or lung function. In multivariable regression models, neither clinical characteristics nor physical or psychological symptom burden scores were associated with CFQ-R physical domains. In contrast, higher scores on Illness Consequences were associated with lower psychosocial CFQ-R scores. Higher scores on the Illness Coherence and Personal Control scales were associated with higher psychosocial CFQ-R scores.

Conclusion

Adults with CF report a high understanding of their disease, feel that CF has significant consequences, and endorse both personal and treatment control over their outcomes. Illness perceptions did not vary with increased age or worsening disease severity, suggesting that illness perceptions may develop during adolescence. Illness perceptions were associated with psychosocial, but not physical, aspects of HRQOL. Efforts to modify illness perceptions as part of routine clinical care and counseling may lead to improved quality of life for adults with CF.

Introduction

Cystic fibrosis (CF) is the most common life-limiting genetic disease affecting the Caucasian population. Due to advances in clinical care, survival of CF patients has increased such that more than 40% of patients with CF in the United States currently are over the age of 18 years [1]. During adolescence and adulthood, CF complications, including worsening obstructive lung disease, chronic infections, malnutrition, CF-related diabetes, and bone disease, frequently arise [2]. Adults with CF often struggle with issues of adherence to daily medical regimens in the face of high symptom burden and a demanding treatment burden [3], [4]. The daily treatment requirements for most adults with CF include use of pancreatic replacement enzymes, monitoring of caloric intake, chest physical therapy, inhaled bronchodilators, inhaled antibiotics, inhaled mucolytics, and anti-inflammatory therapies [2], [5]. Worsening disease severity, combined with these challenges to daily self-management, may impact the overall health-related quality of life (HRQOL) of adults with CF. Previous research into HRQOL in CF has demonstrated significant associations with demographics, markers of disease severity such as frequency of pulmonary exacerbations and daily symptom burden, and measures of psychological health such as depression and mechanisms of coping [3], [6], [7], [8], [9]. In recent years, several patient self-report measures have been evaluated in CF populations as markers of health status and HRQOL. A key marker of health status in chronic disease is symptom burden, which has been characterized in CF with measures such as the Memorial Symptom Assessment Scale (MSAS) [3]. In addition, the Cystic Fibrosis Questionnaire—Revised (CFQ-R) has been validated as a disease-specific HRQOL measure and used as a patient-reported outcome in clinical research trials [10], [11].

Illness perceptions, defined as the manner in which an individual identifies with and understands one's disease, may influence overall HRQOL, especially emotional or psychological well-being. The Illness Perception Model (IPM) posits that organized beliefs about illness and treatment influence quality of life. The central proposition of IPM theory is that patients' beliefs or representations about their illness influence their responses to the challenges of chronic disease self-management, which in turn may influence HRQOL [12]. Cognitive components of illness perception can be broadly divided into knowledge and understanding of the illness and views on how the illness can be managed. The IPM conceptualizes these factors into the following domains: (1) cause: personal ideas about various causes of illness; (2) consequence: views about the expected outcome of the illness; (3) timeline: views about the illness trajectory (particularly the cyclical nature) of chronic disease; and (4) control: views on how to control symptoms. The “cause” domain consists of beliefs about the biological, emotional, environmental, or psychological causes of illness, while the “consequence” domain consists of beliefs about the impact of illness on functional status or overall quality of life. “Timeline” refers to beliefs about the course of the illness and the persistence of symptoms. Finally, the “control” domain consists of beliefs about whether the illness can be controlled [13].

Research based on the IPM suggests that illness perceptions may influence health outcomes such as HRQOL independently of coping strategies [14]. The IPM has been extended to delineate the influence of illness perceptions and treatment beliefs on treatment decisions such as adherence [15], [16], [17]. Additionally, it has been suggested that the IPM holds promise for understanding treatment decisions and adherence in adults with CF [18].

The Illness Perception Questionnaire—Revised (IPQ-R) has been developed and validated as a quantitative measure of the different domains of the IPM [19]. This instrument has been studied in patients with different chronic illnesses, including diabetes, chronic–obstructive pulmonary disease, and asthma, as a way to assess patients' representations of their illness [20], [21], [22]. In a small study of adolescents with CF, the IPQ-R treatment control domain was associated with adherence to treatment [23]. We hypothesized that illness perceptions would also be associated with HRQOL in adults with CF. In addition, we hypothesized that illness perceptions would be affected by health status and daily symptom burden. Therefore, as a part of the Project on Adult Care in Cystic Fibrosis (PAC-CF), we administered the IPQ-R to a cohort of adults with CF in order to explore these relationships between illness perception, health status, and HRQOL.

Section snippets

Study participants

PAC-CF is an ongoing prospective longitudinal panel study of adults with CF. Adults 18 years of age or older were recruited from one of 10 participating CF centers for the study. The design of PAC-CF has been previously described [24]. Recruitment in PAC-CF was based on a stratified sampling design in which each participant was assigned a survivorship score based on a previously validated model of survival in CF [25]. The survivorship score is based on eight clinical characteristics—age,

Results

One hundred ninety-nine PAC-CF respondents completed the IPQ-R (response rate, 73%). The mean age of respondents was 35.8 years, 62% were female, and the mean FEV1 was 62.5% predicted (Table 1).

In general, the respondents agreed with statements included in the Illness Consequences subscale (such as “my CF has major consequences on my life”) and the Illness Timeline—Cyclical subscale (such as “I go through cycles in which my CF gets better and worse”). In contrast, respondents tended to disagree

Discussion

In this study, we have described illness perceptions in a large cohort of adults with CF using a well-validated measure IPQ-R [19] based on the components of the IPM [12] and found that illness perception, particularly the view that CF has significant consequences on daily life, is associated with psychosocial, but not physical, aspects of HRQOL.

Prior research has shown that illness perceptions are associated with numerous health behaviors and outcomes in chronic diseases of childhood onset

Acknowledgments

This work was supported by a grant from the National Heart, Lung, and Blood Institute (R01 HL72938).

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