It's generally accepted that the higher your sleep apnea score (the apnea-hypopnea index, or the AHI), the worse off you'll be in terms of your health or cognitive abilities. However, a recent study from France challenges this viewpoint. The study authors recruited 857 healthy men and women (average age 68) and followed them for 2 years. Extensive cognitive and sleep questionnaires were given at the beginning and the end of the study. At the end of the study, a home-based sleep study was performed, and the results were surprising:
• 53% of healthy 68 year olds had obstructive sleep apnea (defined as an AHI > 15)
• 37% had severe obstructive sleep apnea (AHI > 30)
• No significant differences in daytime sleepiness between subjects with and without obstructive sleep apnea
• No significant differences in anxiety, depression, and cognitive difficulties in those with and without OSA
• Little oxygen drops in those with OSA
• No significant differences in cognitive function and severity of obstructive sleep apnea (except for episodic memory/delayed recall).
Why the discrepancy? It's possible that these healthy people only recently developed obstructive sleep apnea, so the long-term consequences haven't had time to set in. Another possibility is that there are compensatory mechanisms, such as revascularization or other similar mechanisms. A recent study reported similar findings with sleep apnea patients and heart disease.
This explains why I sometimes see older men and women who have severe obstructive sleep apnea and are completely asymptomatic with no medical problems whatsoever. This study doesn't really contradict the known risks associated with obstructive sleep apnea—it only means that there's a subset of the population with sleep apnea that compensate very well. However, I'm wiling to bet that if you followed these people for 10 or 15 years, there will be a higher risk of cardiovascular events and even death.
Do you know anyone that may fit this picture? Please enter your answer in the comments box below.