MED-NERD

Etiology and Epidemiology of Obesity hypoventilation syndrome (OHS)/Pickwickian Syndrome

 

Etiology:

OHS is due to decreased ventilatory drive and capacity as a result of obesity (BMI >30 kg/m2). The increased load on respiratory system in addition to the diminished ventilatory response to carbon dioxide (CO2) lead to daytime hypercapnia. Due to obesity and the increased amount of fat in the body especially around the chest and abdomen, the space available for lung expansion is reduced, resulting in decreased lung capacity overtime. OHS patients do not have the same respiratory drive changes. 

Due to decreased respiratory drive, inspiration and expiration do not adequately wash CO2 from the blood. Researchers attributed the decreased respiratory drive to multiple mechanisms: sleep-disordered breathing, certain genes, and leptin resistance.

Leptin is a hormone produced by adipose tissue (fatty tissue). The function of leptin is to induce the sense of satiety in addition to stimulation of breathing. In case of leptin resistance, leptin levels are elevated with decreased response of the body. Therefore, leptin resistance may affect satiety and breathing.

Risk factors:

The main risk factor of OHS is obesity with BMI > 30 kg/m2 according to the international guidelines. BMI > 40 kg/m2 is considered extreme obesity according to the National Heart, Lung, and Blood Institute (NHLBI). About 0.15%-0.3% of adults with a BMI > 40 kg/m2 having OHS were estimated by experts.

Another risk factor for OHS is obstructive sleep apnoea (OSA). About 10-15% of patients having both obesity and OSA, also have OHS. 

It was found that OHS is more common in males, African Americans, and in Asian communities at which OHS develops at a lower BMI.

Epidemiology:

Due to different sample characteristics, variant assessment processes, and different disease definition, the prevalence of OHS varies in different studies.

Globally:

-About 1 out of 3 adults are overweight with BMI ≥25 kg·m−2.

-About 1 out of 10 adults are obese with BMI ≥30 kg·m−2.

In the United States (US):

In the United States (US), obesity presents in more than a third of the current population. The prevalence of obesity depends on various factors such as age, gender, education, and ethnicity. The highest prevalence of obesity among 40-59 years old individuals, women, less educated, and non-Hispanic Black individuals. Due to the strong relation between Pickwickian syndrome and obesity, increasing obesity means increasing the prevalence of OHS. Recently, Among adults in the US, the prevalence of morbid obesity (BMI ≥40 kg·m−2) is nearly 7.6%-8% according to the Centres for Disease Control and Prevention (CDC). Therefore, the prevalence of OHS is increased in the US due to epidemic obesity.

The prevalence of morbid obesity increased 5-folds in the US with one individual affected out of 33 adults between 1986 and 2005. The prevalence of individuals with BMI ≥50 kg·m−2 has increased in the US by 10-folds with one individual affected out of 230 adults.

In East Asian populations:

OHS may be found in patients with lower BMI compared to the non-Asian populations. Studies showed that the prevalence of OSA is more in males. The prevalence of OHS is nearly equal in both males and females despite that, a study in Saudi Arabia reported that OHS cases referred to the sleep disorders clinic, were more prevalent in older females (15.6%) with mean age 61.5 years than in males (4.5%) with mean age 49.1 years.

See:

-Introduction on Obesity hypoventilation syndrome (OHS)/ Pickwickian Syndrome

-Clinical Presentation and Diagnosis of Obesity Hypoventilation Syndrome (OHS)/Pickwickian syndrome

References:

(1)Ghimire P, Sankari A, Kaul P. Pickwickian Syndrome. [Updated 2022 Nov 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK542216/ 

(2)Masa JF, Pépin JL, Borel JC, Mokhlesi B, Murphy PB, Sánchez-Quiroga MÁ. Obesity hypoventilation syndrome. Eur Respir Rev. 2019 Mar 14;28(151):180097.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9491327/ 

(3)Shah, N.M., Shrimanker, S. and Kaltsakas, G. (2021) Defining obesity hypoventilation syndrome, Breathe (Sheffield, England). U.S. National Library of Medicine. Available at:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8753617/ 

(4)Athayde RAB, Oliveira Filho JRB, Lorenzi Filho G, Genta PR. Obesity hypoventilation syndrome: a current review. J Bras Pneumol. 2018 Nov-Dec;44(6):510-518.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6459748/ 

(5) Jay  Summer (2022) Pickwickian syndrome: Symptoms, causes, and treatments, Sleep Foundation. Available at:

https://www.sleepfoundation.org/sleep-apnea/pickwickian-syndrome