Correlation of Anthropometry With Severity of Obstructive Sleep Apnoea

INTRODUCTION

Sleep-disordered breathing comprises a broad spectrum of sleep-related breathing disorders, including obstructive sleep apnoea (OSA), central sleep apnoea, sleep-related hypoventilation, and hypoxemia. OSA is the most common form of sleep-disordered breathing. It is highly prevalent, but remains underdiagnosed. It is characterised by repeated upper airway obstruction, which causes sleep fragmentation, cardiovascular stimulation, and oxygen desaturation. It is also characterised by recurrent upper airway obstruction resulting in cessation (apnoea) or reduction (hypopnea) of airflow during sleep.^[1] Anatomical changes in the upper airway lead to the development of OSA. Polysomnography (PSG) is the gold standard for diagnosing and grading the severity of OSA.

We conducted a study to correlate the severity of OSA with anthropometric measurements (BMI and neck circumference), Mallampati grading, and Friedman’s grading.

MATERIAL AND METHODS

The cross-sectional study was conducted in the Department of Otorhinolaryngology and the Department of Pulmonary Medicine at KS Hegde Charitable Hospital. Approval from the institutional ethics committee was obtained before the commencement of the study. Subjects diagnosed with OSA after PSG were included in the study after obtaining written informed consent. They were categorised as having mild, moderate, and severe OSA based on the Apnoea-hypopnoea index. Anthropometric measurements [BMI and neck circumference], Mallampati grading for oropharyngeal visualisation, and Friedman’s grading for tongue position and tonsil size were noted in a proforma. These findings were correlated with the severity of OSA.

Statistical analysis of the data was performed using SPSS 24.0. Categorical variables were represented as frequency and percentage. Continuous variables were presented as mean +/- standard deviation. The association between Friedman grading and Mallampati grading anthropometric measurements with the severity of OSA was analysed using the Chi-square test/Fisher’s exact test. A ‘p’ value < 0.05 was considered statistically significant.

RESULTS

In our study, of the 91 subjects, 65% were males and 35% were females. Most subjects were between 40 and 60 years old. About half had severe OSA. The maximum number of subjects was in grades 2 and 3 under Mallampati and Friedman’s grading systems.

Among the subjects with mild OSA, 29.4% had a normal BMI, 47.0% were overweight, and 23.6% were obese. Among subjects with moderate OSA, 26.7% had a normal BMI, 26.7% were overweight, and 46.6% were obese. For those with severe OSA, 4.5% had a normal BMI, 43.2% were overweight, and 52.3% were obese. There was a significant association between the severity of OSA and BMI levels (p = 0.023), with OSA severity increasing in higher BMI categories. [Table 1].

Subjects with mild OSA had the following distribution of Mallampati grades: 41.2%, 41.2%, 17.6%, and 0% were in grades 1, 2, 3, and 4, respectively. In the moderate OSA category, 13.3%, 30.0%, 43.3%, and 13.3% were grades 1, 2, 3, and 4, respectively. For severe OSA, 4.6%, 27.2%, 43.2%, and 25.0% were grades 1, 2, 3, and 4, respectively. There was a statistically significant association between the severity of OSA and Mallampati grading (p = 0.005) [Table 2].

Subjects with mild OSA had the following distribution of Friedmann grades: 47.1%, 35.3%, 17.6%, and 0% were grades 1, 2, 3, and 4, respectively. In the moderate OSA category, 16.6%, 36.7%, 40.0%, and 6.7% were grades 1, 2, 3, and 4, respectively. For severe OSA, 4.5%, 43.2%, 36.4%, and 15.9% were grades 1, 2, 3, and 4, respectively. There was a statistically significant association between the severity of OSA and Friedmann grading (p = 0.005) [Table 3].

In the mild OSA category, the mean neck circumferences for male and female subjects were 38.43 ± 3.86 cm and 41.40 ± 3.09 cm, respectively. The results showed no statistically significant difference in the neck circumference of subjects with mild OSA between sexes (p = 0.099) [Table 4].

For moderate OSA subjects, the mean neck circumferences for males and females were 41.94 ± 2.50 cm and 41.50 ± 3.03 cm, respectively. The results showed no statistically significant difference in the neck circumference of subjects with moderate OSA between sexes (p = 0.665).

In severe OSA subjects, the mean neck circumferences for males and females were 42.94 ± 2.42 cm and 40.08 ± 2.53 cm, respectively. The difference in neck circumference between males and females with severe OSA was statistically significant (p = 0.032), with males having a larger mean neck circumference compared to females.

The average neck circumferences of male and female subjects were 42.10 ± 2.96 cm and 41.25 ± 2.82 cm, respectively. There is no statistically significant difference in neck circumference between the sexes (p = 0.187).

Data analysis revealed a significant correlation between anthropometric measurements, Mallampati grading, and Friedman’s grading with the severity of OSA.

DISCUSSION

OSA is characterised by recurrent upper airway obstruction, resulting in oxygen desaturation during sleep, cardiovascular stimulation, and sleep fragmentation.^[2]

OSA is associated with a variety of symptoms and conditions, such as fatigue, excessive daytime sleepiness, headache, myocardial infarction, arrhythmias, stroke, and an increased incidence of motor vehicle accidents.^[3]

Risk factors of OSA include obesity, male gender, short and thick neck, macroglossia, jaw misalignment, deviated nasal septum, narrow airways, or oropharyngeal crowding due to a swollen, enlarged, or elongated uvula, enlarged tonsils, or lateral wall narrowing.

PSG is the gold standard for diagnosing and grading OSA. A routine polysomnography (PSG) involves the use of a monitoring device to record sleep stages, limb movements, airflow, respiratory effort, heart rate and rhythm, oxygen saturation, and body posture.^[4]

We observed that most subjects were in their fourth to sixth decades of life. One possible explanation for the observed association is the age-related decline in upper airway muscle tone, which increases the risk of upper airway collapse during sleep. Additionally, older adults often have increased fat deposition around the neck and the presence of comorbidities such as obesity and cardiovascular diseases.^[5,6]

Visceral adiposity is considered a significant risk factor for OSA. It highly correlates with OSA severity in older people, regardless of BMI, but general adiposity is more strongly linked with OSA severity in non-elderly.^[5] Our study revealed a significant positive correlation between BMI and the severity of OSA. The results of our present study are similar to those conducted by Leppanen et al., who observed that the frequency of apnea and hypopnea increased with an elevated BMI.^[7]

Yu and Rosen demonstrated that Mallampati grading and FTP are effective measures for assessing OSA risk and possible severity.^[8] However, it requires standardized measures for evaluation, such as using standardized equipment, taking multiple photographs to account for pharyngeal movement, and using machine learning algorithms to improve grading accuracy.

Our study found a significant correlation between higher Mallampati and Friedman grades and an increased severity of OSA. Subjects with Mallampati grades 3 and 4 were more likely to have severe OSA than those with grades 1 and 2. This correlation suggests that Mallampati and Friedman’s grading assesses the visibility of structures in the oropharynx and is a useful predictor of OSA severity.

Neck circumference is a better predictor of OSA than typical signs and symptoms. However, it is not enough to diagnose the condition without sleep studies. In their prospective study, Davis et al.^[9] revealed that the relationship between OSA severity and overall body obesity are affected by neck circumference variance.

de Araujo Lopes et al.^[10] conducted a study in which anthropometric measurements were used to identify children at risk of developing OSA. They reported BMI, neck circumference, hip circumference, waist-to-hip ratio, neck-to-waist ratio, waist circumference, waist-to-height ratio, and facial anthropometric measurements. They concluded that the OSA group exhibited a greater mean difference in neck circumference. Neck circumference is a reliable way to measure and screen for overweight and obesity in various age, sex, and weight conditions.^[11]

CONCLUSION

This study, which aims to correlate the severity of OSA with BMI, neck circumference, Mallampati grading, and Friedman’s grading, has explored the male preponderance of OSA, suggesting underlying biological and anatomical factors that contribute to this disparity. The analysis confirms a linear correlation between higher Mallampati and Friedman grades and increased OSA severity, supporting the usefulness of these grading systems as predictive tools in clinical settings. The findings of our study demonstrated that higher BMI is significantly correlated with increased OSA severity. Also, with the increase in neck circumference, the severity of OSA tends to increase. This study contributes to a deeper understanding of the factors influencing OSA.