Seasonality of Insulin Use in German Outpatients With Diabetes: A Retrospective Analysis.

BACKGROUND: Seasonality in insulin sensitivity has been the focus of controversial literature in the past decades. The aim of this study was to analyze seasonality of insulin use in patients with diabetes who were followed in German general practices.

METHODS: This study included patients affected by type 1 (T1DM) or type 2 diabetes mellitus (T2DM) who received intensified conventional insulin therapy over a period of at least 12 months between 2013 and 2015. The main outcome was the median insulin dose per day (calculated daily insulin doses, CDDs) between June and August (summer) and between December and February (winter).

RESULTS: The present study included 1197 T1DM patients and 3836 T2DM patients from 492 general practitioner or diabetologist practices. The mean age was 45.4 years (SD = 16.2 years) in the T1DM group and 65.2 years (SD = 14.1 years) in the T2DM group. The most frequent basal insulin therapy was insulin glargine (T1DM: 45.7%; T2DM: 41.1%), and the most frequent bolus insulin therapy was insulin lispro in the T1DM group (38.7%) and human insulin in the T2DM group (45.2%). The consumption of basal and bolus insulins did not significantly differ between summer and winter in T1DM individuals (basal therapy: 30.8 international units (IU)/day versus 31.2 IU/day; bolus therapy: 39.4 IU/day versus 37.8 IU/day). This consumption was also similar between the two seasons in the T2DM group (basal therapy: 31.0 IU/day versus 30.6 IU/day; bolus therapy: 44.3 IU/day versus 44.1 IU/day).

CONCLUSIONS: There was no significant difference in the use of basal and bolus insulin therapies between summer and winter in German patients with T1DM or T2DM.