Effect of glycemic control on nocturnal arterial oxygen saturation: A case-control study in type 2 diabetic patients

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There is growing evidence suggesting a deleterious effect of type 2 diabetes on lung function and sleep breathing. The aim of this case-control study was to evaluate whether or not an improvement in glycemic control could arrest or ameliorate nocturnal hypoxemia in type 2 diabetes.


Thirty patients with type 2 diabetes with HbA1c ≥8% (cases) and 10 non-diabetic subjects were analyzed. Controls were closely matched to cases by age, gender, body mass index, and neck circumference. The nocturnal oxygen desaturation index (ODI) was calculated at baseline and 5 days after blood glucose improvement with pharmacological intervention. Four different oxygen desaturation thresholds (reductions in SaO2 ≥ 3%, 4%, 6%, and 8%) as indicators of hypoxemia severity (ODI-3%, ODI-4%, ODI-6%, ODI-8%) were used.


At baseline, patients with diabetes showed a higher number of ODI-3%, ODI-4%, and ODI-6% in comparison with controls. A significant reduction in ODI-3% (29.7 [4.8–107.9] events per hour at baseline versus 24.6 [3.1–97.7] e/h at discharge, P < 0.001), ODI-4% (21.7 [1.6–79.3] versus 14.7 [0.3–79.4], P = 0.003), ODI-6% (9.3 [0.3–71.8] versus 4.0 [0.0–73.7], P = 0.001), and ODI-8% (4.1 [0.0–64.3] versus 1.1 [0.0–69.8], P = 0.033) was observed in patients with diabetes after 5 days of follow-up. However, no changes in ODI events were observed in non-diabetic patients after the same period. No significant changes in weight were observed in either group.


Glycemic control improvement significantly reduces the increased number of nocturnal oxygen desaturations that exist in type 2 diabetes. Although the mechanisms are not yet fully understood, the rapid effect without changes in body weight suggests a central mechanism involving respiratory center output.

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