COPD is characterized by chronic airflow obstruction secondary to chronic bronchitis and/or emphysema. COPD patients reportedly have significant degree of nocturnal sleep symptoms. Some of the sleep related breathing disorders seen in patients with COPD include Obstructive sleep apnea, sleep related hypoventilation and REM related nocturnal oxygen desaturation syndrome. It is a longitudinal observational study. 60 patients both males and females above the age of 40yrs having COPD were randomly selected and distributed into mild moderate and severe grades based in FEV1 and FEV1/FVC ratio following pulmonary function testing. It is found that out of 60 patients following sleep study, proportion of patients with abnormal Apnea hypopnea index were more among grade 2,3,4 (chi square 26.33, p-0.0001) <0.001 which was statistically significant. Also proportion of patients with abnormal Oxygen desaturation index was more as the severity of grading of COPD increased. Early CPAP treatment helped to reduce the severity of sleep disorders and the reduction of AHI and ODI indices.