In Reader’s Digest, Michael J. Breus, PhD, aka The Sleep Doctor, shares the negative effects of undiagnosed sleep apnea. Headaches, especially in the morning, are a common symptom. OSA leads to diminished oxygen levels in the blood and to the brain—one reason scientists think this condition causes headaches. For women, OSA is more common than many people realize. And women’s symptoms aren’t always the same as men’s.