Diabetes Care Volume 37, September 2014
e200
COMMENT ON GUEST ET AL.
Clinical Outcomes and Cost-effectiveness of Continuous Positive Airway Pressure to Manage Obstructive Sleep Apnea in Patients With Type 2 Diabetes in the U.K. Diabetes Care 2014;37:1263–1271
Abd A. Tahrani
e-LETTERS – COMMENTS AND RESPONSES
Diabetes Care 2014;37:e200–e201 | DOI: 10.2337/dc14-1000 The article by Guest et al. (1) addresses a hotly debated topic. While many studies have examined the impact of obstructive sleep apnea (OSA) on glucose metabolism and cardiovascular disease in patients without diabetes, little is known about the impact of OSA on clinical outcomes in patients with type 2 diabetesdhence the importance of the findings by Guest et al. The importance of this area is further emphasized by the high prevalence of OSA in patients with type 2 diabetes (2,3). The impact of continuous positive airway pressure (CPAP) on glycemic measures is unclear. Although uncontrolled studies have shown that CPAP improved glycemic control in patients with type 2 diabetes, the only randomized controlled trial has not shown such benefit (2,4). This could be due to a true lack of effect or to factors related to the study populations and duration and compliance with CPAP (2,5). The current case-control observational study showed an average HbA1c difference of 3.9% between treated and untreated groups by the end of the 5-year follow-up. This resulted from a greater deterioration in glycemic control in the control group compared with the CPAP-treated group. Although these results are intriguing, the deterioration in glycemic control occurred very early
in the study in both groups; the mean HbA1c increased by 1.3% and 5.2% in the CPAP-treated and control groups, respectively, by year 2 of follow-up. Taking into account that the glycemic control did not deteriorate any further (in fact it improved slightly) in the control group despite not having CPAP, these differences observed as early as year 2 are difficult to attribute to CPAP treatment. Although deterioration in glycemic control in patients with type 2 diabetes due to the continuous decline in b-cell function is to be expected, an HbA1c worsening of 5.2% over 1 year in the control group is highly unusual in real-life or research settings. This is supported by the fact that the HbA1c only deteriorated by 0.5% between the two HbA 1c measurements in the control group during year 1. Such significant worsening in HbA1c in the untreated group might reflect factors that were not measured in this observational study. Furthermore, despite the deterioration in glycemic control in the control group over the 5-year period, there appears to have been no significant intensification of insulin treatment. In fact, the prescription of insulin was twice as much in the CPAP-treated versus control group, although this was not statistically significant. In addition, the
CPAP-treated group showed a very high level of compliance with CPAPdmuch more than that reported in research studies (as highlighted by the authors)d and such a group of motivated patients are likely to be adherent to other treatments, including glucose-lowering agents, although objective data about CPAP usage was not available for the majority of the study population. All these factors make it difficult to draw firm conclusions from this study regarding the impact of CPAP treatment on glycemic control. The improvements in blood pressure observed in the study are more compelling, although the observational nature of the study will still limit interpretation of the findings. Well-designed clinical trials of adequate treatment duration are needed to answer the question of the impact of CPAP on clinical outcomes in patients with type 2 diabetes, although early studies suggest a favorable impact (6,7).
Funding. A.A.T. is a clinician scientist supported by the National Institute for Health Research in the U.K. Duality of Interest. No potential conflicts of interest relevant to this article were reported.
References 1. Guest JF, Panca M, Sladkevicius E, Taheri S, Stradling J. Clinical outcomes and cost-effectiveness of continuous positive airway pressure to
Centre for Endocrinology, Diabetes and Metabolism, University of Birmingham, Birmingham, U.K., and Department of Diabetes and Endocrinology, Heart of England National Health Service Foundation Trust, Birmingham, U.K. Corresponding author: Abd A. Tahrani, [email protected]. The views expressed in this publication are those of the author(s) and not necessarily those of the National Health Service, the National Institute for Health Research, or the Department of Health. © 2014 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.
care.diabetesjournals.org
manage obstructive sleep apnea in patients with type 2 diabetes in the U.K. Diabetes Care 2014; 37:1263–1271 2. Tahrani AA, Ali A, Stevens MJ. Obstructive sleep apnoea and diabetes: an update. Curr Opin Pulm Med 2013;19:631–638 3. Tahrani AA, Ali A, Raymond NT, et al. Obstructive sleep apnea and diabetic neuropathy: a novel association in patients with type 2 diabetes. Am J Respir Crit Care Med 2012;186: 434–441
Tahrani
4. West SD, Nicoll DJ, Wallace TM, Matthews DR, Stradling JR. Effect of CPAP on insulin resistance and HbA1c in men with obstructive sleep apnoea and type 2 diabetes. Thorax 2007;62:969–974 5. Grimaldi D, Beccuti G, Touma C, Van Cauter E, Mokhlesi B. Association of obstructive sleep apnea in rapid eye movement sleep with reduced glycemic control in type 2 diabetes: therapeutic implications. Diabetes Care 2014;37: 355–363
6. Mason RH, Kiire CA, Groves DC, et al. Visual improvement following continuous positive airway pressure therapy in diabetic subjects with clinically significant macular oedema and obstructive sleep apnoea: proof of principle study. Respiration 2012;84:275– 282 7. Tahrani AA, Ali A, Raymond NT, et al. Obstructive sleep apnea and diabetic nephropathy: a cohort study. Diabetes Care 2013;36: 3718–3725
e201
e200
COMMENT ON GUEST ET AL.
Clinical Outcomes and Cost-effectiveness of Continuous Positive Airway Pressure to Manage Obstructive Sleep Apnea in Patients With Type 2 Diabetes in the U.K. Diabetes Care 2014;37:1263–1271
Abd A. Tahrani
e-LETTERS – COMMENTS AND RESPONSES
Diabetes Care 2014;37:e200–e201 | DOI: 10.2337/dc14-1000 The article by Guest et al. (1) addresses a hotly debated topic. While many studies have examined the impact of obstructive sleep apnea (OSA) on glucose metabolism and cardiovascular disease in patients without diabetes, little is known about the impact of OSA on clinical outcomes in patients with type 2 diabetesdhence the importance of the findings by Guest et al. The importance of this area is further emphasized by the high prevalence of OSA in patients with type 2 diabetes (2,3). The impact of continuous positive airway pressure (CPAP) on glycemic measures is unclear. Although uncontrolled studies have shown that CPAP improved glycemic control in patients with type 2 diabetes, the only randomized controlled trial has not shown such benefit (2,4). This could be due to a true lack of effect or to factors related to the study populations and duration and compliance with CPAP (2,5). The current case-control observational study showed an average HbA1c difference of 3.9% between treated and untreated groups by the end of the 5-year follow-up. This resulted from a greater deterioration in glycemic control in the control group compared with the CPAP-treated group. Although these results are intriguing, the deterioration in glycemic control occurred very early
in the study in both groups; the mean HbA1c increased by 1.3% and 5.2% in the CPAP-treated and control groups, respectively, by year 2 of follow-up. Taking into account that the glycemic control did not deteriorate any further (in fact it improved slightly) in the control group despite not having CPAP, these differences observed as early as year 2 are difficult to attribute to CPAP treatment. Although deterioration in glycemic control in patients with type 2 diabetes due to the continuous decline in b-cell function is to be expected, an HbA1c worsening of 5.2% over 1 year in the control group is highly unusual in real-life or research settings. This is supported by the fact that the HbA1c only deteriorated by 0.5% between the two HbA 1c measurements in the control group during year 1. Such significant worsening in HbA1c in the untreated group might reflect factors that were not measured in this observational study. Furthermore, despite the deterioration in glycemic control in the control group over the 5-year period, there appears to have been no significant intensification of insulin treatment. In fact, the prescription of insulin was twice as much in the CPAP-treated versus control group, although this was not statistically significant. In addition, the
CPAP-treated group showed a very high level of compliance with CPAPdmuch more than that reported in research studies (as highlighted by the authors)d and such a group of motivated patients are likely to be adherent to other treatments, including glucose-lowering agents, although objective data about CPAP usage was not available for the majority of the study population. All these factors make it difficult to draw firm conclusions from this study regarding the impact of CPAP treatment on glycemic control. The improvements in blood pressure observed in the study are more compelling, although the observational nature of the study will still limit interpretation of the findings. Well-designed clinical trials of adequate treatment duration are needed to answer the question of the impact of CPAP on clinical outcomes in patients with type 2 diabetes, although early studies suggest a favorable impact (6,7).
Funding. A.A.T. is a clinician scientist supported by the National Institute for Health Research in the U.K. Duality of Interest. No potential conflicts of interest relevant to this article were reported.
References 1. Guest JF, Panca M, Sladkevicius E, Taheri S, Stradling J. Clinical outcomes and cost-effectiveness of continuous positive airway pressure to
Centre for Endocrinology, Diabetes and Metabolism, University of Birmingham, Birmingham, U.K., and Department of Diabetes and Endocrinology, Heart of England National Health Service Foundation Trust, Birmingham, U.K. Corresponding author: Abd A. Tahrani, [email protected]. The views expressed in this publication are those of the author(s) and not necessarily those of the National Health Service, the National Institute for Health Research, or the Department of Health. © 2014 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.
care.diabetesjournals.org
manage obstructive sleep apnea in patients with type 2 diabetes in the U.K. Diabetes Care 2014; 37:1263–1271 2. Tahrani AA, Ali A, Stevens MJ. Obstructive sleep apnoea and diabetes: an update. Curr Opin Pulm Med 2013;19:631–638 3. Tahrani AA, Ali A, Raymond NT, et al. Obstructive sleep apnea and diabetic neuropathy: a novel association in patients with type 2 diabetes. Am J Respir Crit Care Med 2012;186: 434–441
Tahrani
4. West SD, Nicoll DJ, Wallace TM, Matthews DR, Stradling JR. Effect of CPAP on insulin resistance and HbA1c in men with obstructive sleep apnoea and type 2 diabetes. Thorax 2007;62:969–974 5. Grimaldi D, Beccuti G, Touma C, Van Cauter E, Mokhlesi B. Association of obstructive sleep apnea in rapid eye movement sleep with reduced glycemic control in type 2 diabetes: therapeutic implications. Diabetes Care 2014;37: 355–363
6. Mason RH, Kiire CA, Groves DC, et al. Visual improvement following continuous positive airway pressure therapy in diabetic subjects with clinically significant macular oedema and obstructive sleep apnoea: proof of principle study. Respiration 2012;84:275– 282 7. Tahrani AA, Ali A, Raymond NT, et al. Obstructive sleep apnea and diabetic nephropathy: a cohort study. Diabetes Care 2013;36: 3718–3725
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