Sleep Apnea Blankets a Host of Nasties
Batch of studies links disorder to CVD, diabetes and bad driving
National Review of Medicine (Canada)
By Owen Dyer

It's long been suspected that sleep apnea goes hand in hand with more serious conditions. That suspicion has a much more solid basis this month, after a slew of research findings implicated sleep apnea in diabetes, heart disease, early cardiovascular death, pre-eclampsia and even car crashes.

The profile of the typical sleep apnea sufferer is already a familiar one in most cardiologists' waiting rooms: male, middle-aged and overweight. It's common for these patients to have several cardiovascular risk factors. But attendees at this year's conference of the American Thoracic Society (ATS) in San Francisco at the end of May heard that the risk of heart disease in sleep apnea patients remains elevated even when standard risk factors are taken into account.

RESTLESS HEARTS
Sleep apnea — defined as an apnea-hypopnea index score over 15 on polysomnography — can increase the risk of heart attack or death by 30%, according to a study led by Dr Neomi Shah of Yale University Medical School. The study followed 1,123 patients over five years, and found that risk increased throughout that period. Patients with the most severe sleep apnea (apnea-hypopnea index score over 30), ran a risk of heart attack or death nearly 30% higher than those with milder apnea symptoms. Patients in the apnea group had higher blood pressure and body mass index than controls, although lipid profiles, arrythmias and smoking status were similar in the two groups. Before these risk factors were controlled for, sleep apnea showed a hazard ratio of 1.56 for heart attack or death, with a significance of P=0.007. After controlling for cardiovascular risk factors, the hazard ratio fell to 1.4, and the finding remained statistically significant at P=0.048.

Dr Shah says in a telephone interview with NRM that the magnitude of the added risk is "clinically important," similar to that conferred by a previous history of heart attack. In obstructive sleep apnea, the airway temporarily collapses, leading to partial arousal of the sleeper. This can happen dozens or even hundreds of times in a night's sleep. The sudden, repetitive decreases of oxygen trigger the sympathetic nervous cascade commonly known as the fight-or-flight response, says Dr Shah. This can raise blood pressure and increase heart rate.