Obstructive sleep apnea syndrome in the Sao Paulo Epidemiologic Sleep Study.

OBJECTIVE

To estimate the prevalence of Obstructive Sleep Apnea Syndrome (OSAS), using current clinical and epidemiological techniques, among the adult population of Sao Paulo, Brazil.

METHODS

This population-based survey used a probabilistic three-stage cluster sample of Sao Paulo inhabitants to represent the population according to gender, age (20-80 years), and socio-economic status. Face-to-face interviews and in-lab full-night polysomnographies using a nasal cannula were performed. The prevalence of OSAS was determined according to the criteria of the most recent International Classification of Sleep Disorders (ICDS-2) from American Academy of Sleep Medicine (2005).

RESULTS

A total of 1042 volunteers underwent polysomnography (refusal rate=5.4%). The mean age+/-SD was 42+/-14 years; 55% were women and 60% had a body mass index>25 kg/m(2). OSAS was observed in 32.8% of the participants (95% CI, 29.6-36.3). A multivariate logistic regression model identified several independent and strong associations for the presence of OSAS: men had greater association than women (OR=4.1; 95% CI, 2.9-5.8; P<0.001) and obese individuals (OR=10.5; 95% CI, 7.1-15.7; P<0.001) than individuals of normal weight. The adjusted association factor increased with age, reaching OR=34.5 (95% CI, 18.5-64.2; P<0.001) for 60-80 year olds when compared to the 20-29 year old group. Low socio-economic status was a protective factor for men (OR=0.4), but was an associated factor for women (OR=2.4). Self-reported menopause explained this increased association (age adjusted OR=2.1; 95% CI, 1.4-3.9; P<0.001), and it was more frequent in the lowest class (43.1%) than either middle class (26.1%) or upper class (27.8%) women.

CONCLUSIONS

This study is the first apnea survey of a large metropolitan area in South America identifying a higher prevalence of OSAS than found in other epidemiological studies. This can be explained by the use of the probabilistic sampling process achieving a very low polysomnography refusal rate, the use of current techniques and clinical criteria, inclusion of older groups, and the higher prevalence of obesity in the studied population.