A study to estimate prevalence and risk factors of Obstructive Sleep Apnoea Syndrome in a semi-urban Indian population

Obstructive Sleep Apnea Syndrome (OSAS) has been recognised as a major cause of morbidity and mortality in developing countries like India. There is still a paucity of Indian studies regarding the prevalence of OSAS. The current single centre prospective cross-sectional study was undertaken to know prevalence estimates for key symptoms and features that can indicate the presence of OSAS in an Indian population. A survey was conducted on subjects with age groups ≥ 25 years at King George's Medical University, Lucknow, Uttar Pradesh, India from August 2009 to July 2011. Data was recorded during the interview on the basis of Berlin Questionnaire (BQ). Risk factors for OSAS were also evaluated. Risk group categorization for OSAS was done with the help of a questionnaire and overnight polysomnography was performed in each group to measure apnea and hypopnea index (AHI). Out of 1816 subjects, 1512 (response rate 83.3%) finally participated in the survey with mean age 42.6±11.2 years, males 67.9% and females 32.1%. Of them 6.2% were found to be at high-risk OSAS; 12.2% were obese (Body Mass Index ≥30 kg/m²) and 33.5% of the obese population were at high-risk OSAS. Among high-risk patients with OSAS, 62.4% had hypertension. Statistically significant and independent risk factors found for OSAS were obesity, large neck size, alcoholism and use of sedatives/tranquillizers. High-risk category predicted an AHI ≥5 with a sensitivity of 86.3% (95% CI 73.1-93.8), specificity of 93.1% (95% CI 89.1-95.7), positive and negative predictive values of 70.9% (95% CI 57.9-81.4) and 97.2% (95% CI 94.1-98.8) respectively. It can be concluded that BQ questionnaire can still be used as a pre-assessment tool for predicting persons at risk for OSAS in clinical practice. Further studies on estimation of prevalence of OSAS by applying BQ are warranted in near future from other regions of India.