Connecting the dots: analysing the relationship between AHI and ODI in obstructive sleep apnea

Abstract

Abstract Background In the lab type-1 Polysomnography (PSG) is the gold standard for the diagnosis of Obstructive sleep apnea (OSA). But in view, the increasing prevalence, highly expensive, and the presence of a pandemic state make it sometimes impractical to perform PSG in all patients suspected of OSA. The objective of our study was to compare the correlation between the gold standard Autoscored Apnea Hypopnea Index (AHI) and Oxygen desaturation index (ODI) based classification of the severity of OSA. Methodology It was a single-centered hospital-based cross-sectional study in which a total of 176 Subjects suspected of OSA were recruited and underwent overnight 7 channels of in-lab polysomnography at AIIMS Patna. Demographic details, comorbidities, and lab data were collected for all enrolled patients. BMI, STOP-BANG score, and Epworth sleepiness score (ESS) were also calculated for all subjects. They were categorized into mild, moderate, and severe OSA based on AHI and ODI values of 5–14.9, 15–29.9, and ≥ 30 events per hour, respectively. Recordings of polysomnography (PSG) were presented with descriptive statistics. Data is presented as the “mean ± standard deviations” for continuous variables and percentage frequencies for categorical variables. The Chi-square test was used to compare the discrete variables. Statistical significance was set at an alpha level of 0.05 with P < 0.05, with a two-tailed probability. Spearman's rank correlation analysis was used to test the strength and direction of the association between OSA severity (using AHI classification) and the Oxygen Desaturation Index. Results The Mean (SD) age of patients enrolled in our study was 47.42(12.60) years with 57.95% males. Among comorbidities, 31.8% (n = 56) were known cases or incidentally diagnosed with Diabetes Mellitus Type 2, 43.18% (n = 76) were hypertensive and 31.8% (n = 56) had hypothyroidism. The mean HbA1c level among Diabetic patients was 6.05 (1.27) and the mean TSH level among Hypothyroidism patients was 12.24 (27.34). There was a positive correlation between AHI and ODI in our study (Pearson’s correlation coefficient = 0.897). Conclusion Good concordance between AHI and ODI makes nocturnal oximetry a less expensive tool to confidently screen patients with severe OSA. This may be applicable in smaller centers where facilities and expertise for a full night PSG may not be easily available.

Keywords

• Obstructive sleep apnea
• Apnea hypopnea index
• Oxygen desaturation index