The implications of dysglycaemia on aerobic exercise and ventilatory function in cystic fibrosis
Adam J Causer1, Janis K Shute2, Michael H Cummings3
1School of Sport, Health & Exercise Science, Faculty of Science & Health, University of Portsmouth, Portsmouth, United Kingdom; Cystic Fibrosis Unit, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom.
Insights
Adults with cystic fibrosis (CF) and related dysglycaemia, including CF-related diabetes (CFRD), show reduced aerobic fitness (V˙O2max). This decline is linked to more severe CF lung disease, not glycaemic control itself.
Area of Science:
- Pulmonary Medicine
- Endocrinology
- Exercise Physiology
Background:
- Reduced aerobic fitness is observed in pediatric cystic fibrosis (CF) patients with CF-related diabetes (CFRD).
- This association has not been previously studied in adults with CF, particularly those with more advanced lung disease.
Purpose of the Study:
- To investigate the relationship between aerobic fitness and glycaemic control in adults with CF.
- To determine if CF-related dysglycaemia impacts maximal oxygen uptake (V˙O2max) in this population.
Main Methods:
- Retrospective analysis of cardiopulmonary exercise and glycaemic control tests in 46 adults with CF.
- Participants were categorized into CFRD, impaired glucose tolerance (IGT), or normal glucose tolerance (NGT) groups.
- Maximal oxygen uptake (V˙O2max) and ventilatory limitation were assessed.
Main Results:
- Adults with IGT and CFRD exhibited reduced V˙O2max compared to those with NGT, but this difference disappeared when lung function was a covariate.
- Ventilatory limitation was more frequent in CFRD and IGT groups than in the NGT group.
- Gender and body mass index predicted V˙O2max, while glycaemic control did not.
Conclusions:
- Adults with CF-related dysglycaemia have diminished aerobic capacity (V˙O2max).
- The reduced V˙O2max is primarily attributed to the severity of underlying CF lung disease.
- Glycaemic status itself does not appear to be an independent predictor of aerobic fitness in this cohort.
Background:
The development of cystic fibrosis (CF)-related diabetes (CFRD) in paediatric groups is associated with a reduced aerobic fitness. However, this has yet to be investigated in adults with more severe lung disease.
Methods:
Cardiopulmonary exercise and glycaemic control tests were retrospectively analysed in 46 adults with CF (age: 26.9 y [range: 16.3-66.5 y]; forced expiratory volume in 1s: 65.3% [range: 26.8-105.7%]; 26 males), diagnosed with CFRD (n = 19), impaired glucose tolerance (IGT; n = 8) or normal glucose tolerance (NGT; n = 19).
Results:
Maximal oxygen uptake (V˙O2max) was reduced in adults with IGT and CFRD compared to their age- and gender-matched counterparts with NGT (p < 0.05); however, there was no difference when lung function was included as a covariate (all p > 0.05). V˙O2max was greater in adults who experienced post-reactive hypoglycaemia vs. NGT without hypoglycaemia (p < 0.05). The frequency of ventilatory limitation (84%, 63% and 37%, respectively; p < 0.05) but not ventilation-perfusion mismatch (42%, 38% and 16%, respectively; p > 0.05), was greater with CFRD and IGT vs. NGT. There was also no difference in arterial oxygen saturation changes between groups (p > 0.05). Gender and body mass index were significant predictors of V˙O2max (adjusted R2 = 0.37, p < 0.01), but glycaemic control did not explain additional variance (p > 0.05).
Conclusions:
Adults with CF-related dysglycaemia had a reduced V˙O2max compared to age- and gender-matched counterparts, due to a greater degree of CF lung disease in these populations.
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