Servicio de Cardiología
Complejo Hospitalario de Jaén
Pza del Zodiaco No. 8, 5B
23009 Jaén
Spain
Tel: +34 637 463857
Fax: +34 953 270692
E-mail address: maapalomares{at}secardiologia.es
Servicio de Neumología
Hospital Universitario La Paz
Madrid
Spain
Servicio de Neumología
Hospital Universitario La Paz
Madrid
Spain
Servicio de Cardiología
Complejo Hospitalario de Jaén
Jaén
Spain
We read with interest the article by Murphy et al.1 who report a significant association between obesity and fatal and non-fatal cardiovascular events in a large, population-based cohort of middle-aged obese patients compared with normal weight subjects followed for 20 years.
These comments are focused on the role of obstructive sleep apnoea (OSA) as another possible factor contributing to the described high rates of cardiovascular events and mortality in obese patients, an aspect not evaluated in this study. OSA is characterized by periodic reduction or cessation of breathing due to narrowing of the upper airways during sleep. Prevalence surveys estimate that 2% of women and 4% of men of middle age are affected by this syndrome.2 In patients with untreated severe OSA, a higher incidence of fatal and non-fatal cardiovascular events has been reported in comparison with that observed in untreated patients with mildmoderate OSA, patients treated with continuous positive airway pressure, and healthy subjects.3 Importantly, it has been estimated that OSA is present in 40%4 to 90%5 of obese subjects. Prevalence of OSA is probably rising as a consequence of increasing obesity, obesity being the most important risk factor for OSA. It may be related to changes in upper airway muscle tone, effects of fat deposition on upper airway anatomic structures, and changes in central mechanisms of breathing control. Obesity and OSA share multiple pathophysiological mechanisms such as endothelial dysfunction, insulin resistance, hyperleptinaemia, systemic inflammation, impaired baroreflex, or sympathetic hyperactivity.6 As a result, OSA may contribute to the presence of cardiovascular events observed in many obese patients.
In contrast, weight loss in OSA patients is associated to reductions in apnoea index,7 and chronic application of continuous positive airway pressure, the treatment of choice for OSA, reduces body fat and visceral fat accumulation in OSA patients.8 Therefore, clinicians must be aware to diagnose and treat obese patients for previously undiagnosed OSA, probably helping to reduce the high rates of cardiovascular events related to both conditions.
References
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