ABSTRACT
Background: Autonomic nervous system balance is altered in cystic fibrosis (CF), although its influence on physical fitness has been poorly explored. Objective: This study aimed to evaluate the association of heart rate variability (HRV) with exercise capacity and levels of daily physical activity in children and adolescents with mild-to-moderate CF. Methods: A cross-sectional study including individuals with CF aged 6-18 years, not under CFTR modulator therapy, was performed. Sociodemographic (age, sex) and clinical information (airway colonization, pancreatic insufficiency, and genotyping) were collected. In addition, exercise capacity (modified shuttle test - MST), lung function (spirometry), body composition (bioimpedance), levels of daily physical activity (5-day accelerometer), and HRV (both at rest and during the MST) were evaluated. Results: 30 individuals (20 females) aged 11 . 2 ± 3 . 7 years, mean FEV 1 62 . 8 ± 27 . 6 %, were included. A sympathovagal balance (LF/HF) increase ( p < 0 . 001 ) during the MST was shown, indicating a predominance of sympathetic modulation. The standard deviation of all RR intervals (SDNN) and the high frequency (HF) index during exercise correlated significantly with FEV1 ( r = 0 . 45 , p = 0 . 01 and r = 0 . 46 , p = 0 . 01 ; respectively). MST distance also correlated positively and significantly with SDNN ( r = 0 . 43 , p = 0 . 01 ), square root of the mean of the sums of squares of frequencies between RR intervals greater than 50 ms - RMSSD ( r = 0 . 53 , p < 0 . 01 ), low frequency - LF ( r = 0 . 48 , p < 0 . 01 ), HF ( r = 0 . 64 , p < 0 . 01 ), dispersion of points perpendicular to the short-term identity line - SD1 ( r = 0 . 40 , p = 0 . 02 ) and negatively with LF/HF ( r =- 0 . 57 , p < 0 . 01 ). Regarding daily physical activity, SDNN at rest ( r = 0 . 37 , p = 0 . 04 ) and exercise ( r = 0 . 41 , p = 0 . 02 ) showed positive correlations with time in moderate-to-vigorous activities. When normalizing the SDNN and classifying individuals as normal or altered, those presenting altered SDNN showed poorest FEV1 ( p = 0 . 001 ) and lower exercise capacity ( p = 0 . 027 ). Conclusion: HRV correlates with lung function, exercise capacity and levels of daily physical activity in children and adolescents with CF. The study highlights the influence of CF on autonomic function and suggests HRV measurement as an easy tool to be used in clinical settings as an alternative marker to monitor CF individuals.
ABSTRACT
BACKGROUND: Studies have shown that sleep disorders occur in cystic fibrosis (CF) patients and may be present before daytime clinical manifestations. OBJECTIVES: To evaluate the presence of sleep disorders among children and adolescents with CF, attempting to identify associations with pulmonary function, nutritional status, days in hospital, and days taking antibiotics. METHODS: Individuals with a diagnosis of CF aged between 6 and 18 years were included. Information on sociodemographic, clinical profile, history of hospitalizations, and use of antibiotics in the last year were collected. Spirometry, bioimpedance, and polysomnography were performed. The presence of nocturnal hypoxemia and obstructive sleep apnea syndrome (OSAS) were evaluated and participants divided according to their presence. RESULTS: Thirty-one patients were included. The prevalence of OSAS was 32.3% and nocturnal hypoxemia was 29.0%. Average nocturnal peripheral oxyhemoglobin saturation (SpO2 ) correlated (P < .001) with forced vital capacity (r = .55) and forced expiratory volume in the first second (r = .62). The higher the percentage of total sleep time (TST) with SpO2 less than 90%, the lower the pulmonary function. Individuals with OSAS and nocturnal hypoxemia had lower spirometric values compared to patients without these disorders, but the nocturnal hypoxemia group also had lower Shwachman-Kulczycki score, longer hospitalization time and antibiotic use. TST with SpO2 less than 90% was associated with length of hospitalization (r2 = .53). CONCLUSION: Children and adolescents with CF have sleep disorders, including OSAS (32.3%) and nocturnal hypoxemia (29%). Individuals with nocturnal hypoxemia presented lower lung function, worse clinical score, and higher morbidity. TST with SpO2 less than 90% was associated with length of hospitalization.