A retrospective cohort study on the association between poor sleep quality in junior high school students and high hemoglobin A1c level in early adults with higher body mass index values

Background: Few epidemiological studies have been performed to clarify the association between glucose metabolism disorders in early adults (20 years old) and physiological and environmental factors, including body mass index (BMI) in junior high school days. Therefore, we examined the association between hemoglobin A1c (HbA1c) level and body size (BMI) in early adulthood and lifestyles, including sleep habits and BMI in junior high school days in Shika town, a small town in Japan, by conducting a retrospective cohort study. Methods: We examined the HbA1c levels and body size (BMI) of 99 early adults who turned 20 years old between 2016 and 2020 and were residing in Shika town, Ishikawa Prefecture. We obtained the information on lifestyles and living environment factors, including BMI, from a questionnaire survey conducted among the subjects during their junior high school days (13–15 years old) from 2009 to 2013. Results: No correlations were observed between the HbA1c levels and the BMI values of the early adults. A two-way analysis of covariance (with the HbA1c levels and BMI values of the early adults as main factors) of the body size and lifestyle habits of the junior high school students revealed that “sleep quality in junior high school” was significantly poorer in the high HbA1c group than in the low HbA1c group in the early adults with high BMI values only. This result was also supported by the logistic regression analysis result. Conclusions: The present results indicate that poor sleep quality in junior high school was associated with the high HbA1c levels of the early adults with higher BMI values, which suggests that good sleep quality in junior high school prevents the development of hyperglycemia. However, the present study did not find any relationship between early-adult BMI and HbA1c level.