Age, facial axis angle predict OSA severity

The apnoea-hypopnoea index (AHI) shows a positive association with age and a negative association with facial axis angle, reports a Singapore study involving Southeast Asian Chinese patients with obstructive sleep apnoea (OSA).

A total of 113 OSA patients diagnosed by overnight polysomnography were enrolled in this retrospective cross-sectional study. The researchers explored the relationship between cephalometric parameters and AHI, controlling for age, gender, and BMI. They used the STROBE guidelines for this study.

AHI was positively associated with age (median regression coefficient, 0.26, 95 percent confidence interval [CI], 0.07–0.44; p=0.006). [Proc Singap Healthc 2024;doi:10.1177/20101058241303772]

AHI also positively correlated with the distance of hyoid bone to mandibular plane (median regression coefficient, 0.58, 95 percent CI, 0.05–1.11; p=0.032). However, this association did not reach statistical significance after Bonferroni correction (p=0.64) or adjustment for age, gender, and BMI (p=0.106).

On the other hand, AHI negatively correlated with facial axis angle (median regression coefficient, –0.53, 95 percent CI, –1.04 to –0.01; p=0.046), after adjusting for age, gender, and BMI.

“Results from this study suggest that the further the hyoid bone was from the mandible, the larger the AHI,” the researchers said. “An inferiorly placed hyoid bone is thought to influence tongue posture, hence affecting the retro-glossal airway dimensions.” 

Previous cephalometric studies that compared OSA patients with control participants corroborate this finding. [Respir Med 2003;97:640-646; Eur J Orthod 2000;22:353-336; Angle Orthod 2007;77:1054-1061]

Moreover, one study comparing OSA patients with their siblings without OSA found that OSA was associated with a greater distance from the hyoid bone to the mandibular plane after correcting for age and BMI. [Sleep 2005;28:315-320]

Gender

The current study also observed that male OSA patients tended to be younger than their female counterparts. This finding supported that of a previous observation study involving 2,827 patients, which reported significantly younger male versus female participants (50.4 vs 56.1 years; p<0.0001). [Sleep Breath 2018;22:241-249]

Another study in Germany also noted later OSA onset in female patients, with AHI significantly increasing only after reaching the age of 50. [J Sleep Res 2019;28:e1277]

"While the exact mechanisms underlying this observation is not fully understood, some authors have postulated biological differences in the pathophysiology of OSA between genders,” the researchers said. [Sleep 2002;25:499-506]

“It was also noted that female OSA patients present with different clinical symptoms, especially when AHI was lower, leading to misdiagnosis or underdiagnosis among female patients,” they added. [Sleep 2004;27:305-311; Sleep Med Rev 2008;12:481-496]

Age

One of the well-known risk factors of OSA is age. An earlier study found a two- to threefold increase in OSA prevalence among patients aged 65 years and above when compared to those aged 30–64 years. [Am J Respir Crit Care Med 1998;157:144-148]

The positive correlation between OSA severity and age was seen in both men and women, with odds ratios ranging from 1.77 to 3.20. [Eur J Orthod 1995;17:45-56; J Sleep Res 2019;28:e12770]

"Similarly, our study found a positive correlation between age and AHI (p=0.006),” the researchers said.