Effect of Continuous Positive Airway Pressure on Hemoglobin A 1c in Patients with Obstructive Sleep Apnea: A Systematic Review and Meta-analysis Imran H. Iftikhar • Robert P. Blankfield Received: 18 April 2012 / Accepted: 15 June 2012 / Published online: 8 July 2012 Ó Springer Science+Business Media, LLC 2012 Abstract Background There is little conclusive data regarding the effect of continuous positive airway pressure (CPAP) on glycated hemoglobin (HbA 1c ). An earlier meta-analysis included two randomized controlled trials (RCTs) and found no significant effect of CPAP on HbA 1c . The meta- analysis presented here was conducted to include all rele- vant observational studies and RCTs on the effect of CPAP on HbA 1c . Methods We searched the PubMed database for all studies published prior to March 2012 for trials of the effect of CPAP on HbA 1c . Data from observational studies and RCTs that met the inclusion criteria were extracted for pre- and post-treatment HbA 1c . Results A total of nine studies that included 151 subjects met the inclusion criteria. The duration of the studies ranged from 41 days to 6 months. The mean net change in the HbA 1c was -0.06 % [95 % CI: -0.24, 0.12] (p = 0.5). Five of the nine studies, with a total of 112 subjects, comprised patients with diabetes mellitus (DM) type 2. The mean net change in HbA 1c for the subjects with DM type 2 was 0.08 % [95 % CI: -0.26, 0.42] (p = 0.65). The mean net change in HbA 1c for subjects with DM type 2 in studies that were at least 3 months in duration was 0.16 % [95 % CI: -0.26, 0.58] (p = 0.45). Conclusions This meta-analysis found that CPAP does not reduce HbA 1c levels when used in the short term. Keywords Continuous positive airway pressure Á Obstructive sleep apnea Á HbA 1c Á Meta-analysis Introduction Obstructive sleep apnea (OSA) is a highly prevalent con- dition [1] that is characterized by repetitive upper-airway obstruction resulting in cyclic intermittent hypoxia during sleep. OSA has been shown to be an independent risk factor for the occurrence of diabetes mellitus (DM) in the adult population [2–5]. Data from cross-sectional epide- miologic studies performed in the general or clinic-based populations show an association between OSA and wors- ening glycemic control [6–11]. Continuous positive airway pressure (CPAP) has been the mainstay of treatment for OSA. Previous studies have shown conflicting results on the effect of CPAP on glycemic control. Some investiga- tors demonstrated a significant reduction in HbA 1c with the use of CPAP [12–14] but others showed no significant reduction [15–19]. There have been two meta-analyses published that have looked at the effect of CPAP on markers of glycemic control [20, 21]. One of these included fasting blood glu- cose and insulin resistance as the main outcomes. The other meta-analysis included HbA 1c as a main outcome but included only randomized controlled trials (RCTs). We conducted this meta-analysis to determine if CPAP treat- ment influences HbA 1c values in OSA patients if one includes observational studies along with RCTs. I. H. Iftikhar School of Medicine, University of South Carolina, Columbia, SC, USA I. H. Iftikhar (&) One Richland Medical Park, Suite 300, Columbia, SC 29203, USA e-mail: Imran.Iftikhar@uscmed.sc.edu R. P. Blankfield School of Medicine, Case Western Reserve University, Cleveland, OH, USA e-mail: blankfieldmd@gmail.com 123 Lung (2012) 190:605–611 DOI 10.1007/s00408-012-9404-x