Sleep Apnea Linked to Alzheimer’s Biomarkers, Offering Latest Avenue for Early Detection

Researchers are increasingly focused on identifying accessible biomarkers for Alzheimer’s disease (AD) pathology, moving beyond costly and invasive testing methods. A new study reveals a significant link between the severity of obstructive sleep apnea (OSA) and elevated levels of key biomarkers associated with AD, potentially opening doors for earlier detection and intervention.

The Connection Between Sleep Apnea and Alzheimer’s Disease

Obstructive sleep apnea, a condition where breathing repeatedly stops and starts during sleep, has long been recognized as a potential contributor to the development of AD. Prior research has established a correlation between OSA and increased levels of amyloid-beta (Aβ) and tau proteins, both hallmarks of AD pathology. Yet, the precise nature of this relationship, particularly concerning plasma biomarkers and markers of neuronal injury, remained unclear.

Study Details and Findings

A study published in Alzheimer’s & Dementia examined the association between OSA severity and various AD biomarkers in 120 cognitively normal older adults participating in New York University sleep and aging studies between 2013 and 2021. ¹ Researchers measured OSA severity using the apnea/hypopnea index, and assessed plasma levels of Aβ40, Aβ42, tau, and neurofilament light chain (NfL) using a single molecule assay. Cerebrospinal fluid (CSF) amyloid and tau levels were measured using enzyme-linked immunosorbent assay.

The findings revealed:

• OSA severity correlated with plasma Aβ40 (r=0.21), Aβ42 (r=0.26), and the Aβ42/Aβ40 ratio (r=0.20).
• Associations between plasma tau and NfL levels were dependent on CSF Aβ42 levels.
• Combining OSA severity with the plasma Aβ42/Aβ40 ratio improved the detection of amyloidosis (area under the curve [AUC]=0.78) and tau pathology (AUC=0.71).

Implications for Early Detection

These results suggest that OSA severity is associated with elevated plasma Aβ levels, as well as elevated tau and NfL levels in conjunction with CSF amyloid. This indicates that a combination of OSA measures and plasma biomarkers could serve as a non-invasive method for detecting early signs of brain amyloidosis and tau pathology, potentially identifying individuals at increased risk of developing AD. ²

Broader Research Context

A systematic review and meta-analysis published in Sleep Medicine Reviews in August 2023, analyzing data from 18 studies with 2804 patients, further supports the link between OSA and AD biomarkers. ³ The analysis found significantly higher levels of CSF amyloid beta-40 and blood amyloid beta (Aβ) and tau proteins in patients with OSA compared to healthy controls. ⁴

Future Directions

Further research is needed to fully elucidate the mechanisms underlying the relationship between OSA and AD pathology. However, these findings highlight the potential for utilizing OSA assessment and blood-based biomarkers as a cost-effective and accessible strategy for identifying individuals at risk of developing Alzheimer’s disease, paving the way for earlier interventions and improved patient outcomes.