Think only obese people get sleep apnea? Think again, says largest study yet

By Dr. Liji Thomas, MDReviewed by Benedette Cuffari, M.Sc.Apr 28 2025

New research in eClinicalMedicine reveals that nearly half of people with obstructive sleep apnea are not obese, challenging long-held assumptions and calling for more inclusive screening strategies.

Study: The relationship between obesity and obstructive sleep apnea in four community-based cohorts: an individual participant data meta-analysis of 12,860 adults. Image Credit: Andrey_Popov / Shutterstock.com

Obesity is considered a primary risk factor for obstructive sleep apnea (OSA); however, few large-scale epidemiological studies have been performed examine the prevalence of obesity among individuals diagnosed with OSA. In a recent study published in eClinicalMedicine, researchers assess the prevalence of both obesity and OSA while also considering the role of age and sex in this relationship.

Risk factors for OSA

OSA is a condition in which the upper airway repeatedly collapses while the individual is sleeping. OSA increases the risk of cardiovascular disease, cognitive decline, reduced quality of life, and mortality.

Obesity is associated with a higher risk of OSA; therefore, weight reduction is often recommended manage this condition. In obesity, fat accumulates around the tongue and upper respiratory tract, thereby narrowing the airway and increasing the risk of its collapse as compared to non-obese people.

Obese individuals with central obesity also typically have smaller lung volumes, which may negatively impact ventilation control. Multiple endocrine, inflammatory, and metabolic factors also contribute to OSA in obesity.

Importantly, a significant proportion of individuals diagnosed with OSA are not obese. Other factors that predispose individuals to OSA include abnormally hyporesponsive upper airway dilator muscles or an unstable ventilatory control system. In these conditions, a narrow skeletal structure, excessively long airway, or larger soft palates could contribute to the development of OSA in the absence of obesity.

About the study

All study participants were assessed for OSA severity using the apnea-hypopnea index (AHI). Apnea was defined as a complete or near-complete cessation of airflow, whereas hypopnea was characterized by a partial reduction in airflow for at least ten seconds. The number of these events every hour of sleep were recorded.   

Mild, moderate, and severe OSA were defined as the presence of 15 or fewer events, between 15 and 30 events, and 30 or more events, respectively.

A total of 12,860 adults with a mean age of 67 years were included in the current study. Data from these individuals were obtained from four cohort studies performed in the United States and Switzerland, thereby making this the largest epidemiological study on OSA to date.

About 56% of study participants were diagnosed with OSA, which was defined by an AHI of five or more events. Moreover, 3,309 adults were considered obese with a body mass index (BMI) of 30 kg/m² or greater.

Prevalence of obesity

Although 31.5% of people with OSA were obese, 44% were considered overweight. Of the study participants diagnosed with moderate-to-severe OSA, 39% and 42% were obese and overweight, respectively. For severe OSA, 47% and 37% of these individuals were considered obese or overweight, respectively.

These findings suggest that OSA, despite often being associated with obesity, is widely prevalent among individuals of normal weight. The misdiagnosis or underdiagnosis of OSA among individuals with a BMI of 25 kg/m² or less further increases their risk of serious health complications associated with this condition.   

Prevalence of OSA

Among obese participants, 74% were diagnosed with OSA, 41% and 18% of whom were diagnosed with moderate-to-severe or severe OSA, respectively. In overweight individuals, OSA and moderate-to-severe OSA affected 61% and 26%, respectively.

Being overweight was associated with a 118% increased risk of OSA as compared to normal weight individuals. In obese people, the risk of OSA increased by nearly five-fold that in normal weight individuals.

OSA was more common among obese males at 81% as compared to 64% of obese females. Comparatively, females with OSA were more likely to be obese than males at 40% and 30%, respectively.

Conclusions

Most study participants with OSA were not obese, with 44% considered overweight and 24% of normal weight or underweight. However, females were more likely to be obese if they were diagnosed with OSA as compared to males. Younger people were also at a greater risk of being diagnosed with OSA as compared to those above 65 years.

Recognizing OSA is not exclusive to obesity highlights the need for personalized treatment plans.”

In the future, screening and treatment strategies for OSA must consider that OSA more frequently occurs in overweight or normal weight people. This observation emphasizes the importance of increasing public awareness about the different risk factors and presentations of OSA.