Relationship between AHI, Oximetric Parameters and Comorbidities in Adult and Elderly Patients with Moderate-to- Severe OSAS: An Observational Study

Background: OSAS is a chronic disease characterised by recurrent episodes of apnoea/hypopnoea, which generate chronic intermittent hypoxia, the main etiopathogenetic factor of OSAS-related comorbidities: cerebro-cardiovascular, metabolic and cognitive deficits. Although it represents a major public health problem, it is under-diagnosed. At polygraphy, the Apnoea-Hypopnoea Index (AHI) identifies the number of obstructive episodes, while the oximetry parameters ODI, T90 and minimum and mean SpO2 measure the severity of chronic intermittent hypoxia. Aim of the Study: To test: 1 the usefulness of oximetry parameters in identifying adult and elderly patients with moderate-severe OSAS at higher risk of comorbidities; 2 whether there is a statistically significant association between oximetry parameters and CIRS-G in the elderly; 3 whether CPAP use >4 hours is a protective factor for comorbidities in the elderly. Materials and Methods: A total of 220 patients with moderate-severe OSAS without respiratory comorbidities were enrolled and data on: anthropometric variables, lifestyle, comorbidities and drug therapy were collected. The MMSE and sleep questionnaires (ESS, PSQI, AIS) were administered. The AHI and oximetric parameters were extracted from the polygraph. A value of <30 and ≥30 was chosen as cut-off for ODI, for T90 <20% and ≥20%, for minimum SpO2 <75% and ≥75% and for mean SpO2 <91% and ≥91%. Pcs were divided into two groups of age <65 and ≥65; for the group with age ≥65, the Comorbidity Index (CI) and Severity Index (IS) of the CIRS-G Scale were calculated. In addition, the patients, who accepted CPAP, were followed up at 1-3-6 months, at 1 year and once a year. Results: A high (OR >1) and statistically significant (p<0.05) risk emerged of having diabetes mellitus with ODI ≥30; heart disease with mean SpO2 <91%; hypertension, diabetes mellitus and heart disease with T90 ≥20%. The increased risk for cognitive deficits and heart disease with AHI ≥30 was also statistically significant (p<0.05). Linear regression analysis showed that the T90 >20% -SpO2 minimum <75% interaction is positively associated with CI of the CIRS-G scale (p<0.05) and that CPAP use >4 hours is negatively associated with CI and IS of the CIRS-G scale (p<0.05). Conclusions: In moderate-severe OSAS, oximetry parameters, beyond the AHI, are useful in identifying those adult and elderly patients at higher risk of comorbidities. During the obstructive event, having a minimum SpO2 <75% for a long time (T90 ≥20%) increases CI in the elderly. Increased compliance with CPAP, the gold standard treatment of OSAS, is a protective factor for comorbidities in the elderly.