# Cognitive impairment in comorbid MDD and OSA: the dual effects of intermittent hypoxia and sleep fragmentation

## TL;DR

This study finds that obstructive sleep apnea worsens cognitive issues in people with depression through sleep disruption and low oxygen levels.

## Contribution

The study identifies intermittent hypoxia and sleep fragmentation as dual contributors to cognitive impairment in MDD-OSA comorbidity.

## Key findings

- MDD-SO patients had higher oxygen desaturation and microarousal index compared to other groups.
- P300 latency was significantly prolonged in MDD patients with OSA compared to those without.
- Sleep fragmentation and hypoxia were positively correlated with prolonged P300 components in MDD-OSA patients.

## Abstract

Major depressive disorder (MDD) and obstructive sleep apnea (OSA) exhibit an elevated comorbidity rate. It is posited that in MDD, comorbid OSA exacerbates cognitive impairment through mechanisms including intermittent hypoxia and sleep continuity disruption (sleep architecture disruption and sleep fragmentation).

This cross-sectional study eventually recruited 245 patients aged 18 to 60 years. The cohort included patients with MDD (n=136), MDD with mild OSA (MDD-MO, n=75), and MDD with moderate-to-severe OSA (MDD-SO, n=34). Clinical symptoms, nocturnal sleep, and cognitive function were assessed using clinical psychological scales, polysomnography (PSG), and the event-related potential P300, respectively. We evaluated the intergroup differences in P300 components and their correlation with sleep parameters.

Compared to the other two groups, the MDD-SO group exhibited significant increases in the Oxygen Desaturation Index (ODI), the proportion of N1 sleep and Microarousal Index (p < 0.05). The MDD-SO group showed a marked reduction in N3 and REM sleep compared to both the MDD-MO and MDD groups (P < 0.05 for both). Additionally, P300 latency was significantly prolonged in the MDD-MO and MDD-SO groups relative to the MDD group (P < 0.001). Multiple linear regression identified AHI and ODI as a significant positive predictor of P2, N2, P3a and P3b latency, and Microarousal Index as a significant positive predictor of N1, P2, P3a, and P3b latency in MDD patients with OSA (all p < 0.05).

The observed associations between prolonged P300 latency and elevated ODI/Microarousal Index raises the possibility that intermittent hypoxia and sleep fragmentation are underlying contributing factors. These two nocturnal disturbances may interact to worsen cognitive dysfunction in patients with MDD-OSA comorbidity.