Impact of Highly Effective CFTR Modulator Therapy on Physical Activity, Sleep, and Sinonasal Symptoms in Preschool Children with Cystic Fibrosis: A Prospective Single-Center Pilot Study

Background: Highly effective CFTR modulation with Elexacaftor/Tezacaftor/Ivacaftor (ETI) markedly improves clinical outcomes in people with cystic fibrosis (CF). Data on its effects on physical activity, sleep, sinonasal symptoms and parent-perceived outcomes in preschool-aged children are limited. Methods: In this prospective, observational, single-center cohort study, ten children with cystic fibrosis (aged 2–6 years) and at least one CFTR variant eligible for ETI were included. Data were collected using wrist-worn Garmin vívofit Junior 2 activity trackers and standardized questionnaires one month before ETI initiation and at 1, 3, 6, and 12 months after start of ETI. Outcomes included step count, minutes of moderate-to-vigorous physical activity, sleep parameters, sinonasal symptoms and parental perceptions. Results: ETI was well tolerated. Sweat chloride levels decreased significantly. Physical activity improved at 3 and 6 months (step count and active minutes/day; p < 0.05) but declined to near-baseline levels at 12 months. Parental assessments of physical and sporting performance showed sustained improvement. Sleep duration remained stable, with no changes in deep or light sleep phases or nighttime awakenings. Sinonasal symptoms remained low. Discussion & Conclusions: Preliminary findings of this pilot study show that improvement in physical activity after three and six months of ETI therapy might be attributable to seasonality as therapy was started in winter months. No changes in sleep duration or sleep patterns are reassuring in young children with CF. ETI therapy was safe and well tolerated. Parental appraisal of their childrens’ physical performance improved after start of ETI. Longitudinal, controlled studies involving larger cohorts are required to validate these findings and to account for potential confounding factors, such as seasonal variation.