Elsevier

Sleep Medicine

Volume 11, Issue 5, May 2010, Pages 441-446
Sleep Medicine

Original Article
Obstructive Sleep Apnea Syndrome in the Sao Paulo Epidemiologic Sleep Study

https://doi.org/10.1016/j.sleep.2009.10.005Get rights and content

Abstract

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/m2. 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.

Introduction

Obstructive Sleep Apnea Syndrome (OSAS) is a significant public health problem associated with hypersomnolence, accidents, cardiovascular morbidity, cognitive impairment, anxiety, depression, and metabolic dysfunction [1], [2], [3], [4], [5].

OSAS can be influenced by both genetics and the environment, and it is important to determine the prevalence of OSAS in specific populations. Although OSAS has been studied in North America, Europe, Asia, Australia, and India, no comprehensive studies have been conducted in South America [6], [7], [8], [9], [10], [11], [12], [13], [14].

Earlier studies estimated that between 3.7% and 26% of the population has an Apnea-Hypopnea Index (AHI) above 5. The prevalence of OSAS, defined by AHI frequency and the presence of hypersomnolence, has been estimated to range from 1.2% to 7.5% [6], [7], [8], [9], [10], [11], [12], [13], [14]. These wide variations are partly the result of the lack of homogeneity in epidemiologic studies. Some studies, for example, were performed in pre-selected population groups (e.g., state agency employees, industrial employees, or clinically referred patients) and included a high number of subjects who were suspected of having OSAS because of their snoring frequency [15]. Moreover, some earlier studies did not include subjects over 60 years of age [6], [9], [10], [11], [12], [13], [14]. Many studies were conducted before the development of the nasal cannula and used a thermistor to record airflow during sleep, which is a less sensitive device to detect abnormal sleep respiratory events. Finally, earlier investigations did not use the most recent criteria for OSAS diagnosis from the International Classification of Sleep Disorders (ICSD-2, 2005) of the American Academy of Sleep Medicine (AASM) [16]. Previously, significant daytime sleepiness and strictly scored apneas and hypopneas (AHI > 5) were required to establish the final clinical diagnosis of OSAS. The definition of OSAS has been changed with the introduction of ICSD-2, including symptoms besides daytime sleepiness in association with an AHI between 5 and 15 or an AHI equal to or higher than 15 obstructive events per hour of sleep regardless of the presence of any complaints.

The aim of the present study, which used current clinical and epidemiologic techniques and procedures, was to estimate the prevalence of OSAS according to age, gender, socio-economic status, and Body Mass Index (BMI) in a probabilistic sample representative of the adult population of Sao Paulo, Brazil.

Section snippets

The population under investigation

Sao Paulo, Brazil is the largest city in the southern hemisphere [17] and had a population of 10,886,518 in January 2008. Studies of genetic markers indicating ancestry have found that there are high levels of ethnic admixture in this population [18].

The protocol for this study was approved by the Ethics Committee for Research of the Universidade Federal de Sao Paulo (CEP 0593/06) and was registered with ClinicalTrials.gov (number NCT00596713). Selected volunteers read and signed an informed

Results

The distributions of gender, age, socio-economic status, and BMI among the sample of Sao Paulo residents (n = 1042) were similar to the demographic projections of the 2000 census (Table 1). Women constituted 55% of the study population, 75% of the population participated in the work force, and 59.9% of the subjects were overweight or obese (BMI > 25 kg/m2).

Weighted prevalence estimates of OSAS symptoms show that 55% of the population experiences sleepiness, 38.9% fatigue, 20.5% report snoring, and

Discussion

This is the first population-based survey of OSAS prevalence carried out in a probabilistic sample representative of a large metropolitan area. The study used comprehensive techniques and procedures and had a very low participant refusal rate (5.4%). The refusal group did not differ significantly from the final sample group in regard to age, gender, socio-economic status, or subjective sleep quality [19]; the prevalence estimates can therefore be assumed to be free from selection bias. In

Acknowledgments

This work was supported by grants from the Associaçao Fundo de Incentivo a Psicofarmacologia (AFIP) and FAPESP (#07/50525-1 to RS-S, and CEPID no. 98/14303-3 to ST). ST, LRAB and JAT received the CNPq fellowship. The authors would like to thank Fernando Colugnati for valuable suggestions and statistical analyses. All the efforts of AFIP’s staff, in particular those of Roberta Siuffi, are deeply appreciated.

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