Relationship between exercise capacity and glucose tolerance in cystic fibrosis.

BACKGROUND

Improved exercise capacity (EC) and normal glucose tolerance (NGT) are independently associated with favorable outcomes in CF, however, little information on this relationship exists in patients with CF.

METHODS

Cardiopulmonary exercise tests, oral glucose tolerance tests (OGTT), and HbA1c values measured within a 12-month period were evaluated on 83 pediatric patients diagnosed with CF. Patients were categorized as having NGT, abnormal glucose tolerance (AGT), or CF-related diabetes (CFRD).

RESULTS

EC decreased as severity of glucose intolerance increased across NGT, AGT, and CFRD groups (P = 0.02). Compared to patients with NGT, patients with CFRD had lower peak VO mL/kg/min (33.0 ± 7.3 vs 41.3 ± 9.4, P = 0.01), lower VO % (81 ± 20 vs 93 ± 17, P = 0.03), and higher HbA1c (6.9 ± 1.7 vs 5.4 ± 0.4, P < 0.01). There was a positive association with age and FEV % with EC in the 17 patients with CFRD. In the 66 patients without diabetes, peak EC was positively associated with FEV % and negatively associated with age, fasting insulin, and insulin 120 min. After accounting for age and FEV %, multivariate analyses indicated that insulin and glucose values at 120 min predicted EC.

CONCLUSIONS

These data provide evidence that poor glucose tolerance is associated with lower EC in pediatric patients with CF. There was a significant relationship between glucose and insulin values obtained by OGTT with EC in a sample of non-diabetic patients with preserved lung function. Future studies are warranted to confirm these findings and investigate the potential role of exercise in the management or prevention of CFRD.