Case Control Study
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Respirol. Jan 8, 2020; 10(1): 1-10
Published online Jan 8, 2020. doi: 10.5320/wjr.v10.i1.1
Relationship between metabolic syndrome and hypercapnia among obese patients with sleep apnea
Yuka Kimura, Takatoshi Kasai, Yasuhiro Tomita, Satoshi Kasagi, Hisashi Takaya, Mitsue Kato, Fusae Kawana, Koji Narui
Yuka Kimura, Sleep Center, Clinical Physiology, Toranomon Hospital, Tokyo 105-8470, Japan
Takatoshi Kasai, Department of Cardiovascular Medicine, Cardiovascular Respiratory Sleep Medicine, Juntendo University Graduate School of Medicine; Sleep and Sleep Disordered Breathing Center, Juntendo University Hospital, Tokyo 113-8421, Japan
Yasuhiro Tomita, Sleep Center, Cardiovascular Center, Toranomon Hospital, Tokyo 105-8470, Japan
Yasuhiro Tomita, Department of Cardiovascular Medicine, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan
Satoshi Kasagi, Koji Narui, Sleep Center, Toranomon Hospital, Tokyo 105-8470, Japan
Hisashi Takaya, Sleep Center, and Department of Respiratory Medicine, Respiratory Center, Toranomon Hospital, Tokyo 105-8470, Japan
Mitsue Kato, Fusae Kawana, Koji Narui, Cardiovascular Respiratory Sleep Medicine, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan
Author contributions: Kimura Y, Kasai T and Tomita Y contributed to conception and design of the study, analysis and interpretation of data, drafted the manuscript, and approved the final version of this article; Kasagi S, Takaya H, Kato M, Kawana F and Narui K contributed to acquisition of data, and interpretation of data, making critical revisions related to important intellectual content of the manuscript; and approved the final version of this article.
Supported by Intractable Respiratory Diseases and Pulmonary Hypertension Research Group, from the Ministry of Health, Labor and Welfare, No. H29-027; Health, Labour and Welfare Sciences Research Grants, Research on Region Medical, No. H30-iryou-ippan-009; MEXT-Supported Program for the Strategic Research Foundation at Private Universities, 2014-2018 (Ministry of Education, Culture, Sports, Science and Technology); JSPS KAKENHI, No. JP17K09527.
Institutional review board statement: This study was approved by the Toranomon Hospital Ethic Board.
Informed consent statement: The requirement to obtain informed consent was waived by Toranomon Hospital Ethic Board using opt-out methods.
Conflict-of-interest statement: Dr. Kasai and Dr. Tomita, and Ms. Kawana and Kato are affiliated with a department endowed by Philips Respironics, ResMed, and Fukuda Denshi. Others report to have no conflicts of interest to declare related to this work.
STROBE statement: The authors have read the STROBE guidelines, and the manuscript was prepared and revised according to the STROBE guidelines.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Corresponding author: Takatoshi Kasai, MD, PhD, Associate Professor, Department of Cardiovascular Medicine, Cardiovascular Respiratory Sleep Medicine, Juntendo University Graduate School of Medicine; Sleep and Sleep Disordered Breathing Center, Juntendo University Hospital, 2-1-1 Hongo Bunkyo-ku, Tokyo 113-8421, Japan. kasai-t@mx6.nisiq.net
Received: August 23, 2019
Peer-review started: August 23, 2019
First decision: November 12, 2019
Revised: December 16, 2019
Accepted: December 23, 2019
Article in press: November 12, 2019
Published online: January 8, 2020
Abstract
BACKGROUND

In the obese patient population, some patients have severe obstructive sleep apnea (OSA) with daytime hypoventilation. Such patients are generally identified on the basis of the presence or absence of daytime hypercapnia, and the condition is called obesity hypoventilation syndrome. However, mechanisms for such daytime hypoventilation remain unclear.

AIM

To investigate metabolic syndrome and daytime hypercapnia association based on hypercapnia prevalence in obese OSA patients in a nested case-control study.

METHODS

Consecutive obese patients (body mass index ≥ 30 kg/m2) who underwent polysomnography due to suspected OSA were included. Among them, patients with severe OSA (apnea hypopnea index ≥ 30/h) were divided into two groups according to the presence or absence of hypercapnia during wakefulness (arterial partial pressure of carbon dioxide ≥ or < 45 Torr, respectively). The characteristics and clinical features of these two groups were compared.

RESULTS

Among 97 eligible patients, 25 patients (25.8%) had daytime hypercapnia. There were no significant differences in age, gender, body mass index, apnea-hypopnea index, and Epworth Sleepiness Scale scores between the two groups. However, patients with hypercapnia had a significantly lower arterial partial pressure of oxygen level (75.8 ± 8.2 torr vs 79.9 ± 8.7 torr, P = 0.042) and higher arterial partial pressure of carbon dioxide level (46.6 ± 2.5 torr vs 41.0 ± 2.9 torr, P < 0.001). Additionally, patients with hypercapnia were more likely to have metabolic syndrome (72.0% vs 48.6%, P = 0.043) and a higher metabolic score (the number of satisfied criteria of metabolic syndrome). In multivariate logistic regression analysis, the presence of metabolic syndrome was associated with the presence of hypercapnia (OR = 2.85, 95%CI: 1.04-7.84, P = 0.042).

CONCLUSION

Among obese patients with severe OSA, 26% of patients had hypercapnia during wakefulness. The presence of metabolic syndrome was independently correlated with the presence of daytime hypercapnia.

Keywords: Arterial partial pressure of carbon dioxide, Hypercapnia, Metabolic syndrome, Obesity hypoventilation syndrome, Obstructive sleep apnea, Sleep disordered breathing

Core tip: Daytime hypercapnia presents with severe obstructive sleep apnea in some obese patients, and the condition is called obesity hypoventilation syndrome. However, the prevalence, characteristics, and other clinical features of hypercapnic obese patients with severe obstructive sleep apnea remain unelucidated. Among 97 obese patients with severe obstructive sleep apnea, 25 had daytime hypercapnia, and they were more likely to have the metabolic syndrome. In multivariable analysis, metabolic syndrome was associated with daytime hypercapnia. Although the cause or consequence remains unclear, coexisting metabolic syndrome may play some roles; thus, clinicians should check for metabolic syndrome in obese patients with severe obstructive sleep apnea.