A retrospective look at the impact of smoking on glycemic control and thyroid status in patients with type 1 diabetes (T1DM)

Smoking is one of the factors that can affect serum glucose in patients with type 1 diabetes (T1DM). Control of T1DM is associated with achieving glycated hemoglobin [HbA1c] levels of approximately 7%, which leads to reduced long-term cardiovascular risk. Thyroid hormones can also affect blood sugar levels. Therefore, appropriate control of diabetes can reduce the risk of developing thyroid disorders and vice versa. The aim of the study is to determine whether smoking affects glycemic control and thyroid function in established type 1 diabetes mellitus (T1DM). Materials and methods: A heterogeneous group of 73 patients aged 39±13 years were examined: men 49 (65.3%), women 24 (32%) with T1DM upon admission to the endocrinology department “St. Georgi” (Plovdiv); smokers 25; non-smokers 48. The following were investigated: blood glucose profile (BGP): serum glucose (mmol/L) at 6, 12, 17, 21, 24 hours; HBA1c (%); FT4 pmol/L; TSH mIU/L; TC: total cholesterol mmol/L; HDL-C mmol/L; LDL-C mmol/L; TAG mmol/L; BMI kg/m2 on admission to the ward. Results: In smokers compared to non-smokers, we found statistically significant, p<0.05: increased fasting serum glucose at 6 hours (15.59±6 mmol/L vs 9.67±3.3 mmol/L); decreased BMI (23.21±4.62 kg/m2 vs 26.16±4.79 kg/m2); HDL-C (1.05±0.35 mmol/L vs 1.57±0.43 mmol/L); as well as increased TSH (1.84±0.99 mIU/L vs 0.85±0.94 mIU/L). HBA1c at admission to the clinic showed no significant difference in smokers compared to non-smokers (9.15±1.66% vs. 10.07±1.98%, p=0.574). Conclusion: Smoking worsens glycemic control and thyroid function in patients with T1DM.