Obstructive Sleep Apnea And Type 2 Diabetes: Complications and Treatments
CPAP may reduce patients' risk of sight-threatening diabetic retinopathy.
Obstructive sleep apnea (OSA) is an independent predictor for diabetic retinopathy (DR) in patients with type 2 diabetes (T2D). The findings from a 4-year longitudinal study were published in the American Journal of Respiratory and Critical Care Medicine.
Quratul A. Altaf, MD, from the Centre of Endocrinology, Diabetes, and Metabolism at the University of Birmingham, United Kingdom, and colleagues sought to determine the relationship between OSA and DR in patients with T2D, the first prospective study to do so. The study found that OSA was independently associated with maculopathy and sight-threatening diabetic retinopathy (STDR) in patients with T2D.
More than 200 adult patients (n=230; 57.0% men; 54.8% white Europeans; 45.2% South Asians) with T2D from 2 outpatient diabetes clinics in the United Kingdom were assessed with an overnight home-based multichannel device. OSA was defined by the American Academy of Sleep Medicine's guidelines (≥4% oxygen desaturation and ≥30% reduction in nasal air flow) and categorized as mild, moderate, or severe based on the apnea hypopnea index (≥5 to <15 events/hour, 15 to <30 events/hour, and ≥30 events/hour, respectively). Patients were excluded if they had been diagnosed with respiratory disease, end-stage renal disease, or nondiabetic retinopathy.
Patients with moderate to severe OSA were offered continuous positive airway pressure (CPAP) therapy, the data from which were recorded for the study. Patients who used CPAP >4 hours/night on 70% of days were considered compliant.
DR/STDR was assessed with 2×45 degrees digital retinal images as part of the annual screening program for patients with T2D. STDR was diagnosed if patients had pre-proliferative or proliferative DR, maculopathy, or photocoagulation.
The overall prevalence of OSA was 63.9% (mild, 37.8%; moderate, 14.8%; severe, 11.3%). The overall STDR prevalence was 36.1%; DR prevalence was 63.5%. Advanced DR and maculopathy occurred in 15.2% and 31.7% of patients, respectively. After adjusting for confounders, OSA was still an independent factor for progressing to pre-proliferative or proliferative DR (odds ratio, 5.2; 95% CI, 1.2-23.0; P =.03).
"Our study has shown that OSA predicted the progression to pre-proliferative and proliferative retinopathy in patients with T2D," noted Abd A. Tahrani, MD, in an email interview with Pulmonology Advisor. "The findings are important, as DR is a leading cause of blindness, and despite improvements in the metabolic control in patients with T2D, retinopathy remains very common. Hence, it is important to identify modifiable risk factors for retinopathy in patients with diabetes."
Other observations include that white European patients, who tended to be older and more obese, with higher systolic blood pressure, had elevated rates of OSA (46.8%) compared with South Asian patients (35.8%). Patients who were compliant with CPAP therapy were significantly less likely to develop pre-proliferative and proliferative DR (P <.001).
"Our observational data also suggest the CPAP treatment might have favorable impact on the progression of DR; this finding will need to be examined in randomized controlled trials," said Dr Tahrani. "The retina might be particularly susceptible to the effects of OSA in patients with T2D due to the nocturnal increase in oxygen demands."
- Patients in the study were assessed with home-based multichannel respiratory devices, rather than in-patient overnight polysomnography.
- The patient population was from 2 hospital-based diabetes clinics; therefore, the results may not be replicable in other populations.
- Two-field, rather than 7-field, images were used to assess DR, which might have missed peripheral retinal lesions.
- The brief follow-up period and few events were insufficient to provide a deeper analysis of the OSA-DR relationship.
The researchers received funding from the National Institute for Health Research UK.
Altaf QA, Dodson P, Ali A, et al. Obstructive sleep apnoea and retinopathy in patients with type 2 diabetes: a longitudinal study [published online June 8, 2017]. Am J Respir Crit Care Med. doi:10.1164/rccm.201701-0175OC