Sleep apnea’s contribution to diabetic nephropathy needs attention

By Sally Robertson, B.Sc.Aug 31 2012

The effect of obstructive sleep apnea syndrome (OSAS) on the development of diabetic nephropathy requires investigation, say researchers.

In diabetes patients, OSAS has unfavorable outcomes due to its negative effect on glucose regulation and should be screened for in patients with diabetes, especially if they are obese, they say.

In addition, large studies should be carried out to establish the interrelation between OSAS and diabetic nephropathy.

"Renal failure progression can be worsened with the presence of OSAS," explain Banu Buyukaydin (Bezmialem Vakif University Faculty of Medicine, Istanbul, Turkey) and colleagues. "In these patients, intermittent hypoxia increases sympathetic activation and inflammatory cytokines but there are few studies concerning the relationship between these two clinical pathologies."

In their assessment of 52 obese patients (mean body mass index 32.4 kg/m²) with Type 2 diabetes and sleeping complaints including snoring and shortness of breath, the researchers found that 37 (71.2%) individuals had microalbuminuria (up to 300 mg/day).

Evaluation of the patients' polysomnography findings according to criteria from the American Academy of Sleep Medicine revealed that 35 (67.3%) had OSAS, defined as a score of 5 or more on the apnea hypopnea index (AHI).

Twenty-five (48%) of the patients had mild OSAS (AHI score 5‑15), six (11.5%) had OSAS to a moderate degree (AHI 15‑30), and four (7.7%) had severe OSAS (AHI ≥30).

As reported in Diabetes Research and Clinical Practice, there was no significant relationship between urinary albumin excretion and all apnea indices, all hypopnea indices, oxygen desaturation indices, mean nocturnal oxygen levels, or duration of sleep time below saturation 90%.

The team points out, however, that the study sample was small and most of the patients had been treated with renin-angiotensin aldosterone system blockers, which have established favorable effects on nephropathy development.

The expected relationship between the two clinical pathologies needs to be investigated in large populations of patients with diabetes, say Buyukaydin et al.

"OSAS and glucose intolerance are interacting pathologies but the effect of OSAS on nephropathy development in Type 2 [diabetes mellitus] patients is an important clinical process that should be investigated," concludes the team.

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