Seasonal fluctuation of lung function in cystic fibrosis: A national register-based study in two northern European populations

Abstract

Background Many risk factors for lung disease in cystic fibrosis (CF) display a seasonal pattern yet it is unclear whether this is reflected in seasonal fluctuations in lung function. Methods We conducted a longitudinal study using CF registries in Denmark and the UK. 471 individuals with a median of 104 FEV 1 measurements per person and 7586 individuals with a median of nine FEV 1 measures per person were included from Denmark and the UK respectively. We estimated the effect of seasonality on percent predicted FEV 1 trajectories using mixed effects models whilst adjusting for clinically important covariates. Results We found no significant cyclical seasonal variation in lung function in either country. The maximum variation in percent predicted FEV 1 around the yearly average was estimated to be 0.1 percentage points (95%CI 0 to 0.21) and 0.14 percentage points (95%CI 0 to 0.29) in Denmark and the UK, respectively. When considering possible step-like changes between the four seasons, we found that lung function was higher in spring compared to winter in the UK (0.34 percentage points, 95%CI 0.1 to 0.59) though the difference was not of clinical significance. Conclusion In both the UK and Denmark there may be small seasonal changes in lung function but this effect is not of clinical importance.

Impact of newborn screening on outcomes and social inequalities in cystic fibrosis: a UK CF registry-based study

“…Following our previous approach10 18 we modelled the longitudinal trajectories of weight for age SD-scores, BMI SD-scores and %FEV 1 using linear mixed effects models for each outcome with random intercept and random slope. We used age as the time scale with the intercept being at 1 and 5 years for weight/BMI and %FEV1, respectively.…”

Cystic fibrosis year in review 2018, part 2

“…In addition to validating higher pulmonary function in Canadian participants, they created an online resource available to other researchers, http://cfpercentile.research.sickkids.ca/. Another report evaluated seasonal fluctuations in pulmonary function using CF registries in Denmark and the UK, including 471 individuals with a median of 104 FEV1 measurements per person and 7586 individuals with a median of nine FEV1 measures per person from the respective countries . The effect of seasonality on FEV1pp trajectories used mixed effects models, adjusting for clinically important covariates.…”

Using registries for research in CF. How can we be sure about the outputs?

“…Registries also are useful to inform healthcare policy in CF and this will be increasingly import as care changes in the next decades with CFTR modulator therapy. In this issue of the Journal of Cystic Fibrosis, three registry studies illustrate some of the value and limitations of these datasets and are a useful opportunity to explore how we might use high quality registry data to extend our understanding of disease and interventions in people with cystic fibrosis [12,14].…”

“…Three further studies use registry data from two independent registries to validate a specific observations (two published in this Issue and one in the European Respiratory Journal) [11,12,14]. This approach is to be commended and encouraged as it reduces the chance of bias in single country cohorts.…”

“…Two further studies explore outcomes using the French and Canadian registries [13,14]. In the first of these an innovative methodological approach is applied using cluster analysis, classification and regression tree (CART) algorithms to identify subgroups of adults with CF with a low risk of death over the subsequent 10 years [12]. The model was developed from registry data in the adult CF population in France and then validated in a cohort from the Canadian registry.…”