Changes in body mass index in sleep apnea patients with a year of continuous positive airway pressure treatment (CPAP) Sleep Apnea Syndrome (SAS) it is highly related to obesity. The main purpose of this study is to determine the variation between Apnea Hypopnea Index (AHI) and Body Mass Index (BMI) on sleep apnea patients after a year of CPAP treatment on the Linde Sleep Center. Results: 104 male patients were included in this study, the variables analyzed were; AHI, BMI, Epworth daytime somnolence. As for the data obtained from BMI, after one year of treatment with CPAP, the BMI showed a significant decrease (p < 0.001). In the daytime sleepiness scale, a significant decrease was also found between pre and post treatment values. Discussion: Evidence has consistently suggested that higher body weight would also have higher levels of AHI, and the improvements in BMI referred to in this study emphasize the importance of proper treatment not only in control of respiratory events, but in the reduction of body weight.