Obstructive sleep apnoea and type 2 diabetes: Whose disease is it anyway?

a pioneering study of OSA, reportedthat OSA affected 2–4% of the general population in 1993. Morerecent reports, taking into accountthe increased prevalence of obesity,estimate that up to 17% of adultshave OSA. Importantly, OSA is com-mon in patients with type 2 diabetesmellitus (T2DM). This prevalencevaries depending on the populationand setting of the study but rangesfrom 20% to as much as 80%. While obesity is an importantcontributor to OSA, less than 50% ofOSA is attributable to obesity. Otherfactors which are also important inOSA include age (older individuals),gender (men greater than women),ethnicity (African Americans andHispanics), and craniofacial abnor-malities. OSA has been associatedwith polycystic ovarian syndrome,hypothyroidism, and less commonendocrine conditions such asacromegaly. Smoking and alcoholconsumption can exacerbate OSA.Several gene polymorphisms havebeen associated with OSA in linewith a complex genetic condition.Obesity is a common risk factor forboth diabetes and OSA. However,emerging evidence suggests a rela-tionship between OSA and diabetesindependent of obesity.OSA belongs to a spectrum ofbreathing disorders during sleep(sleep-disordered breathing) thatrange from simple snoring to com-plete cessation of breathing. OSA ischaracterised by frequent abnormalpauses in breathing during sleep.These pauses are obstructive innature and occur despite respiratoryeffort by the patient. OSA is associ-ated with repetitive blood oxygendesaturation because of lack of air-flow into the lungs. Obstructiveevents during sleep are associatedwith arousals that are often unno-ticed by the patient. These arousalsresult in fragmented sleep thatcauses excessive daytime sleepiness(EDS). This increases the risk ofroad and workplace accidents. Thesymptoms of OSA include snoring,witnessed breath-holds, gasping andchoking, fatigue, reduced alertness,nocturia, morning headaches, refluxoesophagitis, poor memory, lowmood and genderual dysfunction.Some of these symptoms are alsoseen in poorly controlled diabetes,resulting in the possibility of OSAbeing forgotten in patients with dia-betes. Severe OSA can be potentiallylife threatening if left untreated,resulting in heart failure and arryth-mias. There is increasing evidencelinking OSA to vascular, metabolic,haematological and genetic markersassociated with increased risk for cardiovascular disease. Identifying patients with OSA inthe diabetes clinic tends not to occurbecause of lack of awareness of therelationship between the two condi-tions. OSA questionnaires are notvery useful either, because they havenot been designed for the diabetespopulation. Also, diabetes patientsmay not specifically report sleepi-ness. Potential indicators of OSA indiabetes patients include frequentheadaches, acid reflux disease,impotence, poor glycaemic control,and uncontrolled hypertension.