Managing cystic fibrosis: strategies that increase life expectancy and improve quality of life

Recent advances in cystic fibrosis

Cystic fibrosis (CF) is an inherited chronic disease that remains a common cause of morbidity and mortality in affected patients, mostly in the young. A wealth of knowledge has been gained into the genetics, pathophysiology, and clinical manifestation of the disease. In parallel with these new insights into the disease, novel treatments have been developed or are under development that have had a major impact on quality of life and survival. Improvement in the delivery of care to patients in CF centers, using a team-based approach, and constant review of process, and by quality improvement projects, have also had an impact on outcomes in CF.

Nongenetic influences on cystic fibrosis outcomes

PURPOSE OF REVIEW

Despite dramatic improvements over the last several decades, tremendous variation exists in cystic fibrosis (CF) health outcomes. Genetic explanations for variations in disease progression are a promising source of information regarding disease biology and pathophysiology, but an understanding of nongenetic factors provides more immediate tools for improving disease outcomes.

RECENT FINDINGS

The clinical course of CF for any individual with CF is determined by the interaction of genetic endowment (including CFTR and modifier genes), the physical environment (including environmental tobacco smoke, outdoor pollution, and pathogenic microorganisms), the sociodemographic, cultural, and family context (which mediates stress, social support, and disease self-management skills), and variations in delivery and acceptance of healthcare treatments. The evidence linking socioeconomic status (SES) with CF outcomes continues to be strong, and appears to be primarily due to associations with environmental and sociocultural stressors and disease-management behaviors rather than barriers in access to healthcare.

SUMMARY

Attempts to eliminate detrimental environmental exposures, improve disease self-management skills, and ensure consistently optimal healthcare practices will likely decrease variations in outcomes including SES-related disparities. Low SES is an important marker of adverse exposures and outcomes which are present throughout the CF population.

Antagonistic pleiotropy as a widespread mechanism for the maintenance of polymorphic disease alleles

BACKGROUND

Many serious diseases have a genetic basis which, from an evolutionary point of view, should have been selected against, resulting in very low frequencies. The remarkable sustained prevalence of a number of disease-associated alleles is therefore surprising. We believe that antagonistic pleiotropy, when multiple effects of a gene have opposing effects on fitness (e.g., sickle cell disease), may be more widespread than typically considered. We hypothesize that, rather than being an exception to the rule of genetic disorders, antagonistic pleiotropy may be common.

METHODS

We surveyed the medical literature in order to determine whether sufficient evidence exists to reassess the nature of antagonistic pleiotropy; from being considered an unusual scenario to one that is anticipated. We also used a simple population genetic model to examine the feasibility of antagonistic pleiotropy to act as a mechanism to maintain polymorphism for serious genetic disorders even if the benefits are subtle.

RESULTS

We identified a number of examples of antagonistic pleiotropy where the deleterious effect, the beneficial effect, and the exact molecular cause have been demonstrated. We also identified putative cases in which there is circumstantial evidence or a strong reason to expect antagonistic pleiotropy in a genetic disorder. The population genetic model demonstrates that alleles with severe deleterious health effects can be maintained at medically relevant frequencies with only minor beneficial pleiotropic effects.

CONCLUSION

We believe that our identification of several cases of antagonistic pleiotropy, despite the lack of research on this question and the varied natures of the types of these disorders, speaks to both the underappreciated nature of this phenomenon and its potentially fundamental importance. If antagonistic pleiotropy is as common as our research suggests, this may explain why so many serious diseases, even apparently environmentally caused ones, have a genetic component. Furthermore, acceptance of a genome full of antagonistically pleiotropic genetic interactions poses important implications for clinical treatment and disease prevention research, especially genetically based therapies.

Health-related quality of life in cystic fibrosis

PURPOSE OF REVIEW

To review the contribution of various therapeutic interventions on both longevity and quality of life in cystic fibrosis patients.

RECENT FINDINGS

Long-term survival in cystic fibrosis has increased markedly in the past 25 years, largely due to a robust clinical trials program carried out at Cystic Fibrosis Foundation accredited clinical centers in the United States and similar organizations worldwide. Cystic fibrosis patients are recommended complex, time-intensive daily therapies that are often difficult for families and patients to sustain long-term. Recently, attention to the perceived value of a particular therapy on a patient's well being is recognized as important for individualizing therapeutic regimens that provide maximal clinical benefit and are more likely to be adhered to long-term by the patient. Cystic fibrosis care is in a new era in which patient-related outcomes (PROs) for the assessment of health-related quality of life (HRQOL) are regarded with equal importance to medically beneficial therapies.

SUMMARY

Numerous advances in the clinical care of cystic fibrosis have led to improved survival, although definitive correction of the abnormal cystic fibrosis transmembrane regulator protein function remains elusive. Patients struggle to maintain rigorous, time-intensive therapeutic regimens, whereas clinicians strive to identify which interventions preserve quality of life. Cystic fibrosis patients depend on their caregiver's ability to assess both the medical benefit and the contribution to quality of life that therapeutic regimes bring to their disease. Caregivers, in turn, need measures of HRQOL in order to prioritize the various therapeutic interventions that are at their disposal in order to provide not just longevity, but meaningful quality of life.