Sugar control in CF-related diabetes tied to fitness level
Fitter patients had better long-term blood sugar control, study finds
People with diabetes related to cystic fibrosis (CF) who had better long-term sugar control were more fit, a study found, suggesting that keeping blood sugar within normal limits may help improve the ability to exercise.
The study, “The association between dysglycaemia and exercise capacity in cystic fibrosis,” was published in Respiratory Medicine by researchers at the University of Bath and the Adult CF Center in Manchester in the U.K.
In CF, thick mucus accumulates along the airways, making it difficult to breathe. Patients often have trouble with physical activity. Usually, the better a patient’s lung function, the more exercise they can do.
Mucus also accumulates in digestive organs, including the pancreas, which produces insulin that controls how much sugar enters cells from the bloodstream. Many patients have dysglycemia, or abnormal levels of blood sugar. This includes both impaired glucose tolerance (IGT), a warning sign of diabetes risk, and CF-related diabetes (CFRD).
The researchers looked at how well 139 people with CF could exercise. They used a cardiopulmonary exercise test, which measures VO2 max, or how much oxygen a patient can use during exercise. People with CFRD had significantly lower VO2 max than those with normal or mildly impaired blood sugar.
Looking beyond VO2max
When the researchers looked more closely, they found that lung function — measured as FEV1%, or how much air a patient can breathe out in one second — was the driver for the lower VO2 max in people with CFRD. When they took lung function into account, the differences in exercise capacity were no longer statistically significant.
They also found that more people with CFRD or IGT reached their breathing limit during the test, meaning their lungs couldn’t keep up with the exercise. Other factors that affected VO2 max included age, sex, body mass index (a measure of body fat), how many days of intravenous (into-the-vein) antibiotics the patient had needed, and FEV1%.
The researchers also looked at HbA1c, a measure of long-term blood sugar control. They found that that in people with CFRD, higher HbA1c was associated with reduced exercise capacity.
While lung function “is the primary driver of reduced exercise capacity in CF,” other factors also contribute, the researchers wrote. “These factors warrant further investigation into a potential causal relationship,” they wrote.
“A longitudinal study, using continuous glucose monitoring, to assess whether decline in [exercise capacity] can [attenuate] with tighter glycaemic control from insulin, modulator therapy or exercise programme would provide solutions to address the measured differences in this study,” the researchers concluded.
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