Arousal Threshold Score: A New Indicator for Examining the Relationship Between Obstructive Sleep Apnea and Overlap Syndrome - A Retrospective Study

Abstract

Objective: A low arousal threshold (AT) appears to contribute to obstructive sleep apnea (OSA) pathogenesis. However, the role of low AT in OSA and overlap syndrome (OVS) is still unclear. This study is aimed to investigate the value of the AT score, a new method for qualifying AT, for examining the relationship between OSA and OVS, including chronic obstructive pulmonary disease (COPD) and asthma.

Methods: In this retrospective study, a total of 3400 adults diagnosed with OSA at a sleep medicine center were finally included. All patients were stratified into low-, high- and very high-AT score groups according to the previous logistic regression for qualifying AT. Multivariate logistic regression was conducted to evaluate the association between AT score and OVS prevalence. We compared this association with that of the apnea hypopnea index (AHI).

Results: 40.3%, 42.9% and 16.8% of OSA patients had low-, high- and very high AT score, respectively. Compared with the very high AT score, the low AT score was independently associated with the prevalence of COPD (OR = 2.17, 95% CI = 1.09-4.32) and asthma (OR = 4.54, 95% CI = 2.52-8.17). With decreasing AT score, the adjusted ORs of the comorbidities increased stepwise, particularly in some subgroups based on sex, age and BMI. Conversely, the classification of AHI did not show similar values.

Conclusion: In individuals with OSA, low AT is a common pathophysiological feature associated with COPD and asthma. The AT score is a new and effective indicator for evaluating the relationship between OSA and OVS.

Keywords: arousal threshold; asthma; chronic obstructive pulmonary disease; obstructive sleep apnea; overlap syndrome; sleep-disordered breathing.

Figure 1

Study flowchart.

Figure 2

Odds ratio and 95% confidence interval of different levels of AT score and AHI for COPD. Notes: Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for COPD across AT score categories and AHI severity levels. Panels (A and B) show results from Model 1 (adjusted for age, sex and BMI) and Model 2 (further adjusted for cardiovascular comorbidities, smoking status and Epworth Sleepiness Scale score), respectively. The “very high AT score” group served as the reference category. Red markers represent comparisons across AT score groups; blue markers represent comparisons across AHI levels. Bold font indicate statistical significance, and P < 0.05 was considered statistically significant.

Figure 3

Odds ratio and 95% confidence interval of different levels of AT score and AHI for asthma. Notes: Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for asthma across AT score categories and AHI severity levels. Panels (A and B) represent Model 1 (adjusted for age, sex and BMI) and Model 2 (further adjusted for cardiovascular comorbidities, smoking status and Epworth Sleepiness Scale score), respectively. The “very high AT score” group was used as the reference category. Red markers indicate comparisons across AT score groups; blue markers indicate comparisons across AHI levels. Bold font indicate statistical significance, and P < 0.05 was considered statistically significant.