According to the researchers, these findings contrast with increasing incidence rates observed for type 1 and type 2 diabetes in the general population.
The study “Incidence and risk factors of paediatric cystic fibrosis-related diabetes” was published in the Journal of Cystic Fibrosis.
Nearly half of all CF patients develop CFRD, and the condition typically becomes more prevalent as patients age. Although CFRD shares some features with both type 1 (impaired insulin production) and type 2 (insulin resistance) diabetes, it is a clinically distinct condition.
Most patients with CFRD do not show symptoms of diabetes, and organizations like the Cystic Fibrosis Foundation and the International Society of Pediatric & Adolescent Diabetes recommend annuals screening for patients who are 10 or older.
Despite these recommendations, screening-approaches for CFRD vary between centers, which consequently influences the estimated incidence of the condition.
To investigate the incidence of CFRD in a pediatric CF population, researchers extracted data from 2000 to 2016 from the Canadian CF Registry (CCFR), which includes CF patients from 42 accredited CF centers in Canada. Of note, the CCFR is estimated to include data from more than 99% of the Canadian CF population.
Of the 2,326 CF patients (age 10 to 18 years) included in the CCFR collection, 275 had a CFRD diagnosis (median age at diagnosis was 14.9 years).
Results showed that during the study period (2010-2016), the incidence rate of CFRD was 2.1 cases per 100 patient years. Patient years, also called person years, sums up the follow-up years of all included patients in a specific study.
Next, to assess time changes in incidence rates, researchers divided the data into three consecutive periods: Jan. 1, 2000 to Dec. 31, 2005; Jan. 1, 2006, to Dec. 31, 2010; and Jan. 1, 2011, to Dec. 31, 2016. In doing so, they found a similar incidence rate in all three time periods, indicating unchanged rates over time.
Interestingly, when the team analyzed a subset from the CCFR — namely the Toronto CF database — to tone down the different screening practices associated with multi-center data, they found a lower incidence rate (1.2 cases per 100 patient years) compared with the CCFR dataset.
Also, results comparing the three time-periods showed that incidence rates in the subset data reduced with time, contrasting with the findings in the overall CCFR group.
The authors noted that center-specific screening practices or baseline differences (e.g., mutation types or body-mass indexes) could explain the discrepancies observed between the two datasets.
When the team looked at possible CFRD predictors, they found that patients with better lung function (based on forced expiration volume in one second, FEV1%, predicted) were less likely to have CFRD. They also found that CFRD was associated with female gender, a history of allergic bronchopulmonary aspergillosis (exaggerated immune response to the Aspergillus fungus), gastrostomy-tube insertion, and liver disease.
“The incidence rates of CFRD are stable, if not decreasing, over time, in contrast to the rising rates of type 1 and type 2 diabetes in the general pediatric population,” the researchers wrote.
The team argued that CFTR modulators might provide beneficial outcomes in patients with CFRD. However, the patients in the current study were not treated with these therapies.
“This epidemiological data will allow for future comparative analyses of incidence rates of CFRD after the widespread introduction of CFTR modulators,” the researchers added.