Screening for Obstructive Sleep Apnea in Type 2 Diabetes Patients – Questionnaires Are Not Good Enough

The shorter life expectancy of patients with type 2 diabetes caused by cardiovascular and cer-ebrovascular diseases compels clinicians to make a systematic effort to address traditional cardio-vascular risk factors, such as dyslipidemia, hypertension, hyperglycemia, obesity, and smoking. However, another major cardiovascular risk factor substantially influencing the quality and length of life – obstructive sleep apnea syndrome (OSA) – is frequently overlooked. OSA is characterized by a repetitive upper airway obstruction during sleep leading to intermittent hypoxemia and sleep fragmentation. Numerous epidemiological studies have proved that untreated OSA represents an independent risk factor significantly increasing all cause as well as cardiovascular, cerebrovascular, and cancer mortality (1–7). The importance of OSA is underscored by its considerable prevalence ranging from 5 to 10% in the general population and is even higher in the population of type 2 diabetes patients where a prevalence of ~70% was reported (8–10). Furthermore, ~90% of all subjects suffering from moderate or severe OSA remain undiagnosed (11). Acknowledging the clinical significance of untreated OSA, the American Diabetes Association's Standards of Care recommend the active treatment of OSA when diagnosed (12), while the International Diabetes Federation's guidelines emphasize the need for systematic OSA screening in all patients with type 2 diabetes (13). The suggested screening approach is split into two steps. In step one, patients fill in a questionnaire stratifying respondents into high or low risk of having OSA. Subsequently, in step two, high-risk patients undergo home sleep monitoring consisting of overnight registration of pulse oxymetry, preferably combined with nasal flow measurement and other accessory signals. Although such a two-step approach seems intuitively attractive, it should be noted that there are currently no studies supporting this approach or validating any of the available questionnaires in a population of type 2 diabetes patients. In fact, the recommendation suggesting a two-step OSA screening procedure is not based on any scientific evidence. Since the performance characteristics of screening questionnaires substantially influence the outcome of the whole screening procedure, this article scrutinizes the key features of available questionnaires and their performance. Subsequently, we will discuss the clinical and ethical impact of OSA questionnaire screening in populations with high cardiovascular risk such as patients with type 2 diabetes. The overarching goal of this article is to advocate OSA screening in type 2 diabetes patients using simple home sleep monitoring devices instead of inaccurate and therefore potentially dangerous questionnaires. Screening questionnaires were introduced to improve the …