More than one in three adults in São Paulo has obstructive sleep apnea, according to the fourth edition of one of the most rigorous population sleep studies ever conducted in the Americas.
The EPISONO study, led by Sergio Tufik and colleagues at the Instituto do Sono and the Universidade Federal de São Paulo (Unifesp), estimated the prevalence of obstructive sleep apnea (OSA) at 37.1% across the adult population of Brazil's largest city. Published in the Journal of Sleep Research, the study stands out because it did not rely on questionnaires or self-reported snoring. Every participant spent a full night in a sleep laboratory undergoing polysomnography — the gold-standard test that measures brain waves, breathing, blood oxygen, and body movement.
What the Study Found
Researchers recruited 769 residents through a four-stage probabilistic sampling method designed to mirror the city's population by age, sex, and socioeconomic status. Each underwent in-lab, full-night polysomnography, with OSA diagnosed according to the most recent American Academy of Sleep Medicine criteria.
The headline numbers:
- 37.1% overall adjusted prevalence of obstructive sleep apnea
- 44.9% of men versus 30.8% of women
- 11.5% of participants had moderate OSA and 7.9% had severe OSA
- Prevalence climbed steadily with age, peaking in the oldest groups
The three factors most strongly associated with having OSA — and especially with the moderate-to-severe forms that carry the greatest health consequences — were advancing age, higher body mass index, and being male.
A Rising Tide Over Time
What makes EPISONO unusual is its history. The third edition, carried out in the first decade of this century, was the first large-scale study in the Americas to use polysomnography on a representative urban sample, and it estimated OSA prevalence at roughly 32.9%.
Comparing across editions suggests the burden is growing. The jump from about 33% to 37% tracks with rising obesity and an aging population — the same forces driving sleep apnea numbers upward in many countries. Because both editions used the same rigorous in-lab method in the same city, the comparison is more reliable than most cross-study estimates, which are often muddied by differences in testing technology and diagnostic thresholds.
These results underscore the need for public health actions based on scalable prevention strategies and equitable access to sleep apnea therapies.
Why It Matters Beyond Brazil
Obstructive sleep apnea is not just a matter of loud snoring and daytime fatigue. Left untreated, it is linked to high blood pressure, heart disease, stroke, type 2 diabetes, and cognitive decline. Yet the large majority of people who have it remain undiagnosed, attributing their symptoms to stress or aging.
The EPISONO findings put hard numbers on a problem that is often estimated indirectly. Because the study captured a representative slice of a megacity of more than 12 million people — using the same objective testing a doctor would order for an individual patient — its prevalence figures carry unusual weight. They also mirror the direction of global research: a Samsung Health study released for World Sleep Day 2026 found nearly one in four people worldwide showing signs of sleep apnea risk, and a population study of 2.9 million people tied the condition to a 71% higher risk of cardiovascular events or death.
The Access Challenge
Identifying that more than a third of a population has OSA raises an obvious question: who will diagnose and treat them all? Full-night polysomnography is expensive and requires specialized labs, and continuous positive airway pressure (CPAP) therapy — the standard treatment — depends on equipment and follow-up support that are unevenly distributed. In Brazil, access to sleep testing and treatment through the public health system (SUS) remains limited relative to the scale of need the EPISONO numbers imply.
That gap is why the study's authors frame their findings not as an academic curiosity but as a call for scalable prevention and more equitable access to therapy. Emerging tools — from wearable screening devices to home sleep tests and, potentially, the first oral drugs for sleep apnea — could help close that gap, but only if they reach the populations that need them most.
For now, the clearest takeaway from EPISONO's fourth edition is a simple one: in one of the world's largest cities, sleep apnea is not a niche disorder. It is a condition that affects more than a third of adults, most of whom do not yet know they have it.
