Sao Paulo Epidemiologic Sleep Study: rationale, design, sampling, and procedures

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.

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.

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%.

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.