Prevalence and clinical feature of the "overlap syndrome", obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease (COPD), in OSA population.

Purpose: The association of chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA), defined overlap syndrome by Flenley, is frequent. Aims of the present study were to assess the frequency of overlap syndrome in 168 consecutive OSA patients, and to evaluate the functional pulmonary hemodynamic, and polysomnographic consequences of this association by comparing Overlap patients with OSA patients.

Methods: From the results of the pulmonary and polysomnographic investigation, patients were classified as OSA patients (group 1), having an apneas/hypopneas index (AH/I) > 15/hr, and Overlap patients (group 2), i. e. OSA patients with an obstructive spirographic pattern (FEV1<60%, FEV1/FVC<65%, RV>130%, RV/TLC>140% of predicted value) not reversible after beta2 agonist inhalation. Group 1 consisted of 135 Patients (115 males, 20 females, age 56+/-10 yr, BMI 32+/-6 Kg/m(2)); the group 2 included 33 patients (30 males, 3 females, age 56+/-11 yr., BMI 34 +/- 6 Kg/m(2)).

Results: The OSA and Overlap patients were similar in most respects: age, BMI, clinical characteristic. In awake Overlap patients had lower PaO(2), higher PaCO(2) and Ppa (p<0.001), and an obstructive spirographic pattern, as compared to OSA patients. During sleep the overlap group had a higher AH/I and a lower mean SaO(2) (p<0.05), a reduction of the sleep efficency (p<0.05), and a reduction in the duration of 1NREM and REM sleep stage (p<0.05), as compared to group 1.

Conclusion: In conclusion, an associated COPD is observed in more than 19% of OSA patients. Overlap patients are at increased risk of developing pulmonary hypertension and show a poorer quality of sleep as compared with OSA patients. The possibility of developing cor pulmonale should be given particular attention in the diagnosis and follow-up of Overlap patients.