Seasonal variation of HBA1C in children and adolescents with type 1 diabetes

Abstract EN

Objective: If HbA1c levels vary by season, evaluation of quality of care using HbA1c levels may be biased without adequately considering the seasonal effect on HbA1c.

The aim of this study is to measure whether there is a seasonal variation in glycosylated hemoglobin concentrations and insulin dose used in children and adolescents with type 1 diabetes.

Methods: A total of 118 children and adolescents with type 1 diabetes mellitus (45 boys and 73 girls), <18 years of age (10.03±3.9), attending the Iraqi Diabetic Center in Al-Mustansiriya Medical College, Baghdad, were included in this cross-sectional study, with diabetes onset before 2005, they were studied over one year in a cohort 2005-2006.

HbA1c, insulin dose and recurrent severe hypoglycemia, were registered at visits scheduled quarterly, but not standardized in time.

Seasonal mean values were calculated for HbA1c (defined by age, sex) and insulin dose for each season over one year. Results: Lower mean HbA1c was seen in summer (7.85±2.28%), and higher in winter (9.04±2.38%), with a highly significant seasonal variation (p=0.0001), but there was no significant seasonal variation in insulin dose.

Seasonal mean values for HbA1c in both sexes were higher in winter and lower in summer, with a significant seasonal variation in males (p=0.023), and females (p=0.035), and a highly significant seasonal variation ( p= 0.001) in patients <13 years only.

Highest percent (62.1%) of measurements which indicated poor control (HbA1c>8.0%) was in winter, but the lowest (34.6%) was in summer. Conclusions: A seasonal variation in the concentration of the HbA1c was observed with the lowest level in summer consistent with an improved metabolic control in the diabetic children during the summer period.

These effects are likely attributable to cold climate, with higher HbA1c levels in winter and lower levels in summer.

A seasonal pattern of HbA1c appeared in both sexes and in patients <13 years old.

Such variation wasn’t related to recurrent severe hypoglycemia.