Continuous positive airway pressure (CPAP) therapy for obstructive sleep apnea (OSA) in patients with type 2 diabetes mellitus (T2DM) and diabetic macular edema (DME) did not improve visual acuity compared with usual care alone, according to the results of a study published in the European Respiratory Journal.

The presence of OSA is particularly high in patients with T2DM and diabetic retinopathy and maculopathy. In those with DME, the prevalence of OSA is 34% to 35%, and undiagnosed OSA is common in patients with T2DM. Treatment of OSA includes weight loss and CPAP therapy, which helps prevent intermittent hypoxia. Proposed mechanisms believed to be involved in the pathogenesis of diabetic retinopathy include hypoxia, oxidative stress, and inflammation.

Researchers investigated the hypothesis that CPAP therapy in patients with T2DM, OSA, and DME would result in improvements in vision. A total of 131 patients who had significant DME that was causing visual impairment were randomly assigned to either usual ophthalmologic care or usual care plus CPAP therapy. The patients were ages 30 to 85 years and were selected from 23 centers in the United Kingdom. Visual impairment was defined as a LogMAR score of 0.92 to 0.14.

The investigators found no significant differences in LogMAR scores at 3, 6, or 12 months between the CPAP and control groups (mean LogMAR at 12 months, 0.33 vs 0.31, P =.39). Furthermore, there was no correlation between changes in LogMAR and average CPAP use. At 3 months, the investigators found increased central macular thickness in the CPAP group, indicating worsening edema, compared with the control group (339.4 μm vs 312.6 μm, respectively; P =.045); however, at 6 months and 12 months, they found no significant differences for this end point. Median daily CPAP use was 3.33 hours at 3 months, 3.19 hours at 6 months, and 3.21 hours at 12 months. Only 19% of participants used CPAP for ≥4 hours for 60% to 100% of nights at 3 months. This percentage increased to 27% at 6 months but was 22% at 12 months.

There are currently no other randomized controlled trials to address the issue of whether CPAP can improve DME in those with T2DM and OSA, according to the investigators. They noted that there is considerable interest in the use of CPAP to treat a number of conditions associated with OSA, including hypertension, insulin resistance, T2DM, and cardiovascular disease.

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The level of CPAP adherence may not have been sufficient to affect visual acuity, but no differences were found between high and low CPAP users for this end point. CPAP may be unable to reverse established damage in DME. Conversely, the authors suggested that best ophthalmic care may stabilize and improve vision, whereas CPAP may not be able to reduce DME further. Future studies might investigate whether CPAP could be used to prevent diabetic retinopathy rather than reverse it or delay its progression.

Reference

West DS, Prudon B, Hughes J, et al. Continuous positive airway pressure effect on visual acuity in patients with type 2 diabetes and obstructive sleep apnoea: a multicentre randomised controlled trial [published online August 30, 2018]. Eur Respir J. doi:10.1183/13993003.01177-2018