a cross - sectional study was carried out in 20092010 on a randomly selected sample of adults aged 15 years and over . the review board for medical ethics of the isfahan university of medical sciences approved the study and methods . we used a two - step approach for the survey . in the first step , then , we randomly selected one lane from each area , by drawing lots , and all the doors of the living places of the selected lanes were knocked and all inhabitants 15 years of age or older were invited to take part in interview and complete the questionnaire . the first part included detailed history of obstructive pulmonary diseases which was taken with special emphasis on symptoms of copd or asthma . diagnosis of chronic obstructive pulmonary disease was based on european respiratory society ( ers ) guidelines.13 the second part consisted of the berlin questionnaire that is well known worldwide and has been adopted and used in previous studies in iran.14 the completed questionnaires were reviewed by one pulmonologist , and any subject who admitted to have current asthma , wheeze ever and chronic bronchitis were invited for pulmonary function tests ( pft ) . the measurement of spirometry were conducted with a commercially available system ( ms - ios ; masterlab - ios , erich jaeger , germany ) , which has been described elsewhere , and fulfilled standard recommendations.15 and subjects who were high risk for sleep apnea by berlin questionnaire were invited for full night polysomnography . the psg consisted of 14 channel continuous polygraphic recording from surface leads for 2 electroencephalography , 2 electro - oculography , chin electromyography , electrocardiography , sensors for nasal airflow ( thermistor ) , tracheal sounds ( microphone ) , thoracic and abdominal respiratory effort ( piezo - electric ) , finger pulse oximeter , leg movements , body position and light . apnea was defined as the cessation of airflow at the nostrils and mouth for more than 10 s. hypopnea was defined as a reduction in oronasal air- flow by at least 30% for 10 s or more accompanied by at least 4% fall from the baseline oxygen saturation ( sao2 ) . hypopnea index ( ahi ) was defined as the total number of apnea and hypopnea events per hour of sleep and was calculated during total sleep time . the output report of each subject was scrutinized qualitatively by one pulmonary physician ( b.a . ) before inclusion for statistical analysis . ( 1)high risk for sleep apnea based on berlin sleep questionnaire categories.14(2)asthma ever was defined as any history of dyspnea attacks combined with wheezy breathing any time in life.4(3)current asthma was defined as any history of dyspnea attacks combined with wheezy breathing in the last 12 months.4(4)chronic bronchitis was defined as productive cough for more than three consecutive months in at least two consecutive years in the absence of any known etiology.4(5)obstructive spirometry was applied to those with fev1/fvc ratios of less than 70%.4(6)osas was diagnosed in patients who had an ahi > 5.5 
  high risk for sleep apnea based on berlin sleep questionnaire categories.14 asthma ever was defined as any history of dyspnea attacks combined with wheezy breathing any time in life.4 current asthma was defined as any history of dyspnea attacks combined with wheezy breathing in the last 12 months.4 chronic bronchitis was defined as productive cough for more than three consecutive months in at least two consecutive years in the absence of any known etiology.4 obstructive spirometry was applied to those with fev1/fvc ratios of less than 70%.4 osas was diagnosed in patients who had an ahi > 5.5 statistical analysis was performed using spss software version 15.0 ( spss , inc . the data were expressed as frequency number and percent . those variables with initially significant effect ( p<0:05 ) where selected for logistic regression analysis and , odds ratios and 95% confidence intervals ( cis ) were calculated and recorded . ( 1)high risk for sleep apnea based on berlin sleep questionnaire categories.14(2)asthma ever was defined as any history of dyspnea attacks combined with wheezy breathing any time in life.4(3)current asthma was defined as any history of dyspnea attacks combined with wheezy breathing in the last 12 months.4(4)chronic bronchitis was defined as productive cough for more than three consecutive months in at least two consecutive years in the absence of any known etiology.4(5)obstructive spirometry was applied to those with fev1/fvc ratios of less than 70%.4(6)osas was diagnosed in patients who had an ahi > 5.5 
  high risk for sleep apnea based on berlin sleep questionnaire categories.14 asthma ever was defined as any history of dyspnea attacks combined with wheezy breathing any time in life.4 current asthma was defined as any history of dyspnea attacks combined with wheezy breathing in the last 12 months.4 chronic bronchitis was defined as productive cough for more than three consecutive months in at least two consecutive years in the absence of any known etiology.4 obstructive spirometry was applied to those with fev1/fvc ratios of less than 70%.4 osas was diagnosed in patients who had an ahi > 5.5 statistical analysis was performed using spss software version 15.0 ( spss , inc . the data were expressed as frequency number and percent . those variables with initially significant effect ( p<0:05 ) where selected for logistic regression analysis and , odds ratios and 95% confidence intervals ( cis ) were calculated and recorded . ( 1)high risk for sleep apnea based on berlin sleep questionnaire categories.14(2)asthma ever was defined as any history of dyspnea attacks combined with wheezy breathing any time in life.4(3)current asthma was defined as any history of dyspnea attacks combined with wheezy breathing in the last 12 months.4(4)chronic bronchitis was defined as productive cough for more than three consecutive months in at least two consecutive years in the absence of any known etiology.4(5)obstructive spirometry was applied to those with fev1/fvc ratios of less than 70%.4(6)osas was diagnosed in patients who had an ahi > 5.5 
  high risk for sleep apnea based on berlin sleep questionnaire categories.14 asthma ever was defined as any history of dyspnea attacks combined with wheezy breathing any time in life.4 current asthma was defined as any history of dyspnea attacks combined with wheezy breathing in the last 12 months.4 chronic bronchitis was defined as productive cough for more than three consecutive months in at least two consecutive years in the absence of any known etiology.4 obstructive spirometry was applied to those with fev1/fvc ratios of less than 70%.4 osas was diagnosed in patients who had an ahi > 5.5 the data were expressed as frequency number and percent . those variables with initially significant effect ( p<0:05 ) where selected for logistic regression analysis and , odds ratios and 95% confidence intervals ( cis ) were calculated and recorded . the actual adult population of the selected 100 lanes was 3900 of whom 3,770 subjects ( 96.6% ) agreed to take part in the study . the population consisted of 2002 females ( 53.1% ) and 1768 males ( 46.8% ) aged 1592 years . the study population age groups and smoking status are presented in table 1 . around half of the population 298 ( 7.9% ) of population were smoker . population disease condition and participation for pft and psg are presented in table 2 . the prevalence of wheeze ever , current asthma and chronic bronchitis in the whole group was 6.8 % , 3.1% and 5.7% , respectively table 2 . using multiple regression analysis , current asthma and wheeze ever , lost their significance and were excluded from results . chronic bronchitis history and obstructive pulmonary function test had significant association with high risk for sleep apnea and positive polysomnography study which are presented in table 3 . population age groups and smoking condition population disease condition and participation for pft and psg predictors of risk of high risk berlin questionnaires and ahi > 5/hour using multiple logistic regressions . the main finding of our study was that in a large randomly selected group of an isfahan population , prevalence of copd in the high risk group of sleep apnea by berlin questionnaire was more than that in the rest of the studied population . we also have shown that copd diagnosed by pulmonary function test , and sleep apnea syndrome diagnosed by polysomnography occurred more frequently together than expected and that the condition s were independently associated with each other . in this cross sectional study , we have shown that obstructive sleep apnea was not more frequent in patients with asthma . our study was based on a random sample of population more than 15 years old in isfahan - iran . sampling was accurately random , the overall response was good at 96.6% but female sex preponderance might indicate lower participation rates for men . some previous studies have reported a higher prevalence of snoring among asthmatic patients compared with non - asthmatic patients16 and some other had reported high prevalence of asthma in patients with osa.12 but , in our study no significant correlation was found between osa and current asthma or wheeze ever . in a recently published study , authors stated that osa appeared to be common in patients with copd or asthma in an urban outpatient pulmonary clinic . but , they said that the high prevalence of osa in oad patients appeared to be due to obesity , and reduced pulmonary function was not an independent risk factor for osa.17 but , in our study we found that sleep apnea syndrome was more frequent in patients with obstructive pulmonary function test . the available data have shown conflicting results also for copd , with one study showing an association between copd and osa,18 while another study in copd patients showed that copd in subjects with osas was as frequent as that in the general population.19 our study has shown that patients with copd had around 3 times more sleep apnea by polysomnography . in agreement with us , one published study from primary care clinic in greece stated that copd patients are twice as likely as others to present sleepiness symptoms.18 another study observed significant differences in both quantity and quality of sleep between patients with stable mild to moderate chronic obstructive pulmonary disease and respective controls.20 our study had potential limitations . first of all , due to very low response rate for polysomnographic study , less than half of the group studied underwent full psg . second , most of our data were derived based on the questionnaire results . in conclusion , in these preliminary results , our data suggested that there was direct relation between osa and copd ; and copd and osa may mechanistically be linked .
background : the aim of this study was to evaluate epidemiological relationship between chronic obstructive pulmonary disease and sleep apnea syndrome in a sample of persian population.methods:as a part of a population - based cross - sectional study , 3900 randomly selected individuals aged 15 years or older were invited to take part in the survey ; 3770 individuals ( 96.6% ) agreed to fill out the respiratory and sleep questionnaire . those subjects suspected to have either chronic obstructive pulmonary disease and/or obstructive sleep apnea underwent spirometry and polysomnography test if indicated . 
 spirometric measurements were performed on 420 invited responders . 
 polysomnography measurements were performed on 25 of the responders.results:prevalence rates for sleep apnea , chronic obstructive pulmonary disease and current asthma were 4.98% , 5.7% and 3.1% , respectively . 
 logistic regression showed independent associations between sleep apnea and chronic obstructive pulmonary disease . 
 there was no significant independent association between sleep apnea symptoms and current asthma and wheeze ever.conclusions:these observations indicated relationship between chronic obstructive pulmonary disease and obstructive sleep apnea . 
 these observations indicated the necessity of further studies to explain the possible common pathogenic mechanisms involved in two disease entities .