Obstructive sleep apnoea can significantly increase a person’s risk for sudden cardiac death, according to the largest study of its kind published online in the Journal of the American College of Cardiology.1

The association of sleep apnoea with cardiovascular risk factors such as hypertension and atrial fibrillation is well documented, as is its link with a higher risk of myocardial infarction. This is the first study to establish a clear relationship between sleep apnoea and sudden cardiac death.

The study followed 10,701 subjects monitored by polysomnogram for incidents of resuscitated or fatal sudden cardiac death (average follow-up 5.3 years). In that time, 142 patients experienced this event, the most common predictors being aged >60 years, having >20 apnoea episodes per hour and having a lowest oxygen saturation level of <78% (p<0.0001). The study showed that a drop of oxygen saturation to below this level increases that patient’s risk of sudden cardiac death by 80%.

The study authors warn that the prevalence of sleep apnoea in Western populations is likely to grow, due to the increasing incidence of obesity. They suggest further research into the mechanisms of sudden cardiac death in these individuals.

Meanwhile, a separate study published in the Journal of Psychiatric Research found that poor sleep, particularly waking too early, appears to play a significant role in raising levels of inflammation among women with coronary heart disease. The elevated inflammation affected only women, not men, even when adjusted for medical, lifestyle and socio-demographic differences, according to the authors.

Since the women in the study were largely post-menopausal, the researchers hypothesised that lower levels of oestrogen may help explain the inflammatory activity associated with poor sleep and that, conversely, testosterone may have a protective effect.