A 37-year-old man reports daytime fatigue and snoring with nocturnal oxygen desaturation. What is the most likely diagnosis?

• A. Depression
• B. Narcolepsy
• C. Hypothyroidism
• D. Obstructive Sleep Apnea

Answer: (D)

Daytime fatigue with snoring and nocturnal oxygen desaturation points to obstructive sleep apnea. This condition happens when the upper airway repeatedly collapses or becomes obstructed during sleep because the pharyngeal muscles relax and lose tone. Each obstruction can cause a partial or complete drop in oxygen levels and triggers brief awakenings to reopen the airway, leading to non-restorative sleep and daytime sleepiness. Risk factors include obesity and male sex, but the pattern of snoring with oxygen desaturations is characteristic regardless.

Depression can cause fatigue and sleep disturbance but doesn’t typically feature repeated nocturnal desaturation from airway obstruction. Narcolepsy presents with excessive daytime sleepiness, sudden sleep episodes, and sometimes cataplexy or hallucinations, not the pattern of snoring with overnight oxygen dips. Hypothyroidism can cause fatigue and weight gain, but it does not characteristically produce the recurrent nocturnal airway collapse and desaturation seen in obstructive sleep apnea.