The Effect of Obstructive Sleep Apnoea on Type 2 Diabetes Mellitus

Obstructive sleep apnoea is a breathing disorder characterized by collapsed upper airways, further leading to cessation of airflow during breathing. This creates low oxygen levels in the blood, further leading to frequent arousals, disturbed sleep and increased daytime sleepiness. This can also further elevate blood sugar levels by decreasing insulin sensitivity and glucose effectiveness.

A recent article from World J Diabetes by Nannapaneni et. al has elaborated that sleep apnoea can indeed have certain effects on Type 2 Diabetes mellitus. What are these effects? 

According to the researchers, obstructive sleep apnoea induces a severe state of insulin resistance and in turn, insulin resistance is a risk factor for cardiovascular disease. Thus untreated sleep apnoea can result in marked compensatory hyperinsulinemia and thereby increasing the requirement for higher doses of exogenous insulin. This is according to several studies quoted by the authors. Insulin resistance may be due to hypoxia and sleep fragmentation caused by obstructive sleep apnoea.

It may also be observed that up to 40% of patients with OSA have diabetes, however the incidence of new diabetes cases among people with sleep apnoea is not known. Also among diabetics, about 23% have obstructive sleep apnoea. It is said that there is a certain relationship between sleep disordered breathing, fasting insulin, glucose, and HbA1c levels which may be independent of obesity.

In addition to these facts, it is said that obstructive sleep apnoea can also speed up the progression of blood vessel complications of Type 2 diabetes mellitus. These complications include retinopathy, nephropathy, neuropathy and macrovascular vascular disease such as coronary artery and cerebrovascular disease or stroke. This may be due to an increase in the inflammatory markers in people with obstructive sleep apnoea. Studies have shown that treatment with continuous positive airway pressure (CPAP) can decrease the levels of inflammatory markers and can reduce vascular complications.

Obstructive sleep apnoea can speed up the development of proliferative retinopathy leading to blindness in Type 2 diabetics. This may also be due to an increase of inflammatory markers and certain growth factors that affect the small blood vessels of the eye.

Diabetic nephropathy or kidney failure may also result. This may also be due to various inflammatory mediators and growth factors that give rise to scarring of the nephrons of the kidney. There is also a rise in inflammatory mediators brought about by low oxygen levels in the blood during sleep apnoea episodes.

Aside from these complications, obstructive sleep apnoea can give rise to peripheral neuropathy due to metabolic and ischemic pathways. It is said that CPAP can bring about good control of blood glucose levels and certain positive effects among diabetics. More studies are needed as to other effective means of treating sleep apnoea among diabetics.

Reference:

Nannapaneni S, Ramar K, Surani S. Effect of obstructive sleep apnoea on type 2 diabetes mellitus: A comprehensive literature review. World J Diabetes. 2013 Dec 15;4(6):238-244.

Image  Courtesy of renjith krishnan / freedigitalphotos.net