Cystic fibrosis (CF) is an autosomal recessive disease that is the result of variants in the cystic fibrosis transmembrane conductance regulator (CFTR) gene that encodes the CFTR protein.1 This change results in altered chloride conductance, particularly in epithelial cells and ultimately leads to multi-organ dysfunction.1 Historically, CF was considered a pediatric disease as most patients did not survive past childhood. However with the advent of newborn screening for CF as well as multiple new therapies, including highly effective modulator therapy (HEMT) which enhances the function of the CFTR protein, ∼60% of people with cystic fibrosis (PwCF) in the United States are now over the age of 18.2

The two most common endocrinopathies associated with CF are cystic fibrosis-related diabetes (CFRD) and cystic fibrosis-related bone disease (CFBD).3,4 The prevalence of CFRD increases with age with a prevalence of CFRD of 20% in adolescents and up to 50% in adults.4 CFRD is associated with unfavorable outcomes such as decreased lung function, poor nutritional status, and reduced bone mineral density.4, 5, 6 Conversely, CFBD, a form of osteoporosis and premature bone loss, affects up to 25-78% of PwCF.7, 8, 9, 10 PwCF experience progressive bone loss with age.11 The Cystic Fibrosis Foundation (CFF) recommends routine screening for CFRD by age 10 and for CFBD by age 8 if risk factors are present or age 18 without risk factors.12 Both conditions can have a significant impact on overall CF disease trajectory including morbidity and mortality.12,13

Healthcare transition (HCT) is defined as the intentional movement from one healthcare system to another, usually from a family-centered, parent-driven, pediatric care model to a more individual and autonomously focused adult care model.14 HCT is a vulnerable phase for emerging adults as many obstacles exist during this time including increased patient responsibility, life changes, insurance gaps, and fewer resources, including physician specialists, available to adult patients.14,15 This can lead to discontinuity and decreased engagement between emerging adults and the healthcare team, resulting in a decline in health.14 Structured transition from pediatric to adult care has been shown to improve chronic disease stability and outcomes.14,16 The American Diabetes Association does offer guidelines in the care of emerging adults with type 1 and type 2 diabetes. This includes preparing emerging adults for transition over several years to months prior to the actual transfer of care and supporting emerging adults in identifying an adult endocrinologist in order to avoid gaps in care upon transfer.17 The adult provider should ideally be knowledgeable in the care and unique needs of emerging adults with diabetes.17 Of note, a standardized protocol to complete these HCT goals has not yet been identified. There is a structured general CF transition program at the care center where the study took place, although there is not a particular endocrine focus. Although more PwCF are now going through transition and the incidence of CF-related endocrinopathies increases with age, there is a paucity of literature examining progression of CFBD and CFRD during emerging adulthood.

Our aim was to examine disease evolution through analysis of hemoglobin A1c (HbA1c) levels and bone mineral density (BMD) in emerging adults during transition from pediatric care up to ten years in adult care. Additionally, we estimated completion rates in screening tests for CFRD by oral glucose tolerance tests (OGTT) and for CFBD by dual-energy x-ray absorptiometry (DXA). We hypothesized that emerging adults with CF experience increased HbA1c levels and decreased BMD during transition due to the recognized difficulty of emerging adults becoming fully autonomous in their healthcare.