Sleep apnea is a sleep-related breathing disorder characterized by repeated pauses in breathing during sleep, with each episode lasting 10 s or longer and causing oxygen levels to drop. The condition takes three main forms—Obstructive Sleep Apnea (OSA) where throat muscles relax and block airways, Central Sleep Apnea (CSA) where the brain fails to send proper breathing signals, and Complex Sleep Apnea Syndrome (CompSAS) in which central apneas persist or emerge during treatment of obstructive sleep apnea with positive airway pressure therapy. Sleep apnea affects 9% to 38% of adults, with risk factors including obesity, age, sex, craniofacial anatomy, and lifestyle. Without treatment, it can trigger a cascade of serious health problems—the repeated oxygen drops stress the cardiovascular system, leading to increased risk of heart attacks and strokes, while disrupted sleep damages brain function, potentially accelerating cognitive decline and neurodegeneration. Sleep apnea also interferes with metabolism, increases diabetes risk, and causes dangerous daytime sleepiness that substantially increases accident risk. Treatments options include continuous positive airway pressure (CPAP), respiratory assist devices, weight management, and, in selected cases, surgery, with early intervention and diagnosis essential to prevent long-term health consequences.