Elsevier

Sleep Medicine

Volume 10, Issue 6, June 2009, Pages 679-685
Sleep Medicine

Special Section in Sleep Medicine
Sao Paulo Epidemiologic Sleep Study: Rationale, design, sampling, and procedures

https://doi.org/10.1016/j.sleep.2008.11.001Get rights and content

Abstract

Objectives

To present the rational design, sampling, and procedures utilized in an Epidemiologic Sleep Study carried out in 2007 to establish the epidemiologic profile of sleep disorders in the adult population of a large metropolitan city, Sao Paulo, Brazil.

Methods

A population-based survey adopting a probabilistic three-stage cluster sample of Sao Paulo was used to represent the population according to gender, age (20–80 years), and socioeconomic class. Questionnaires, actigraphy, polysomnography (PSG), and blood samples were collected to investigate associations between sleep patterns and disturbances according to social-demographic status, activity/rest cycle, physical activity habits, mood disturbances, memory complaints, sexual dysfunction in males, drug addiction, genetic markers, and anthropometric, clinical, biochemical, hematological, endocrine, immunologic, and inflammatory indicators.

Results

A total of 1101 questionnaires were administered at home. A total of 156 volunteers were substituted, who were equivalent to the remaining sample in terms of age, gender, and socioeconomic class. A total of 1042 volunteers underwent PSG recordings at a Sleep Institute, and the refusal rate was 5.4%.

Conclusion

The Sao Paulo Sleep Study is a pioneering investigation, incorporating and integrating up-to-date methodologies for understanding sleep profiles and sleep disorders in large populations. This study will provide reliable information for the planning of health policies and programs aimed to control such disorders and their consequences in the city of Sao Paulo and similar urban environments.

Introduction

Although sleep medicine has existed for only four decades, the specialty has given rise to novel investigations and clinical research activities. Investigation of sleep epidemiology has helped to promote social, labor, and public policies supporting the recognition of the impact of sleep disorders on society. Population-based surveys featuring random sampling are defined as the gold standard to describe sleep disorders in the population [1]. Rarely are such studies feasible, however, because of ethical, methodological, operational, technical, and/or financial constraints. The available estimated sleep disorder prevalence presents a number of methodological limitations [2], [3]. Differences in sampling schemes, disparities in techniques used for monitoring sleep, and variability in sleep disorders definitions can alter disease prevalence and potentially preclude a comprehensive estimate of both symptomatic and asymptomatic disorders [4], [5], [6], [7], [8], [9], [10]. Hence, methodologically comprehensive and sound investigations into the epidemiology of sleep are still lacking in the literature. While some of the initial studies presented most, if not all, of the above limitations, relatively consistent estimates of disease prevalence across several population cohorts have emerged [11], [12].

The Sao Paulo Epidemiologic Sleep Study was thus implemented to (1) establish the epidemiologic profile of sleep disorders in the adult population of Sao Paulo in 2007; (2) investigate the associations between the population’s sleep patterns and disorders related to social-demographic status, activity/rest cycle, eating and physical activity habits, mood disturbances, memory performance, male sexual dysfunction, alcoholism, drug addiction, genetic markers, and anthropometric, clinical, biochemical, hematological, endocrine, immunologic, and inflammatory indicators; and (3) compare the results collected in the current study with those of the Sao Paulo sleep surveys carried out in 1987 and 1995 [13] in order to assess secular trends in sleep disorders. The present paper presents the rational design, sampling, and procedures used in the Sao Paulo Epidemiologic Sleep Study.

Section snippets

The population under investigation

The city of Sao Paulo is the largest in the southern hemisphere and is located at the center of one of the major metropolitan regions of the globe. According to the National Institute of Demographics and Statistics (IBGE) (www.ibge.gov.br), its population reached 10,886,518 inhabitants living within 1524 km2 in January 2008, corresponding to a population density of 7233 inhabitants/km [2]. Practically all ethnicities are represented in the city inhabitants because the slave trade from Africa and

Results

Data gathering, including pre-test procedure, lasted from July 2nd to December 22nd, 2007. A total of 1101 HI questionnaires were applied (1056 sample volunteers plus 45 pre-test volunteers). To reach the total sample, 165 volunteers were substituted after three unsuccessful attempts to contact the target individual, total refusal to participate, obstruction by a family member, or inability to participate for a specified reason (e.g., travel, agenda, hospitalization). A test of homogeneity [23]

Discussion

The Sao Paulo Epidemiologic Sleep Study is a pioneering investigation incorporating and integrating up-to-date methodologies to provide greater understanding of sleep profiles and sleep disorders in large populations. This study will provide reliable information for the planning of health policies and programs aimed to control such disorders and their consequences in the city of Sao Paulo and similar urban environments.

The use of objective assessments of sleep patterns and disorders by PSG and

Acknowledgments

We would like to thank the Associaçao Fundo de Incentivo a Psicofarmacologia (AFIP) and the Fundacao de Apoio a Pesquisa do Estado de Sao Paulo (FAPESP) for their financial support in the current study, and Fernando Antonio Basili Colugnati for statistical analyses support.

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