MM-Net: A Multimodal Multi-Task Network for Sleep Staging and Sleep Apnea Assessment After Ischemic Stroke

Md Wahiduzzaman Suva; Esm E Moula Chowdhury Abha; Md Imtiaj Alam Sajin; Md Iftekharul Mobin; Jia Uddin

cs.LGOct 27, 2026

MM-Net: A Multimodal Multi-Task Network for Sleep Staging and Sleep Apnea Assessment After Ischemic Stroke

Authors: Md Wahiduzzaman Suva, Esm E Moula Chowdhury Abha, Md Imtiaj Alam Sajin, Md Iftekharul Mobin, Jia Uddin

Organizations: Department of Computer Science and Engineering, American International University-Bangladesh, Dhaka, 1229, Bangladesh · AI and Big Data Department, Woosong University, Daejeon, Republic of Korea

Abstract

Automated polysomnography after ischemic stroke is challenging because of altered sleep-related neural activity and concurrent respiratory disturbances. Existing stroke-specific approaches mainly address sleep-stage classification, leaving joint analysis of sleep architecture and respiratory events underexplored. Moreover, adapting pretrained EEG encoders introduces a representation inconsistency when downstream models are trained on embeddings from previously seen patients but evaluated on unseen individuals. We propose MM-Net, a multimodal multi-task framework that resolves this inconsistency through cross-fitting and ridge-based embedding alignment. Sleep-adapted EEG-EOG representations and engineered neural descriptors are fused with learned cardiorespiratory features through cross-attention and shared temporal modeling for simultaneous sleep staging and respiratory-event detection. On iSLEEPS (99 patients with subacute ischemic stroke), ten-fold patient-independent evaluation achieved 76.3% staging accuracy (Cohen's $κ$ = 0.656) and 0.825 respiratory-event AUC, outperforming the evaluated baselines under matched protocols. The sleep-adapted encoder improved the downstream model when its embeddings were aligned, raising staging accuracy by 1.4 percentage points over the frozen encoder ( $p$ = 0.020) versus 0.2 points without alignment. MM-Net also achieved 86.4% staging accuracy on Sleep-EDF, above every single-EEG architecture reimplemented on the same recordings, and 80.3% staging accuracy with 0.889 respiratory AUC on ISRUC-I, exceeding its retrained staging baselines. Without retraining, the iSLEEPS-trained model retained respiratory AUCs of 0.833 on ISRUC-I and 0.841 on UCD. These findings support representation-consistent neural adaptation and joint physiological modeling across stroke, healthy-sleep, and sleep-disorder cohorts.

Figures & tables

Dataset	Population	Data used	Role
iSLEEPS [ 31 ]	Subacute ischemic stroke	99 patients	Development and in-domain evaluation
Sleep-EDF [ 27 , 16 ]	Healthy sleep	40 recordings	Reimplementation checks, healthy-sleep reference, and external staging
ISRUC-Sleep I [ 28 ]	Sleep disorders	100 patients	Cross-validation and transfer (staging, respiratory, AHI)
ISRUC-Sleep II [ 28 ]	Sleep disorders	8 subjects, two nights each	Cross-validation and transfer
ISRUC-Sleep III [ 28 ]	Healthy	10 subjects	Cross-validation and transfer
UCD [ 40 ]	Suspected sleep apnea	25 patients	Transfer (staging, respiratory, AHI)

Table 1: Datasets used in the study and their roles in the evaluation.

Stage	W	N1	N2	N3	REM
Share (%)	26.7	10.1	42.3	8.9	12.1

Table 2: Sleep-stage distribution in the analyzed iSLEEPS cohort (

N=99

;

92{,}560

epochs).

Figure 1: Patient-level respiratory-event burden in iSLEEPS, measured as the fraction of 30-s epochs containing the onset of a scored respiratory event. The dashed line denotes the cohort median of

13\%

Figure 2: The two-stream, multi-task model. The neural stream combines $188$ engineered descriptors with the embedding of a LaBraM encoder adapted to sleep from EEG and EOG and integrated by cross-fitting and alignment; the cardiorespiratory stream is a convolutional encoder over eight raw channels. The streams are fused and read by a bidirectional LSTM over a $20$ -epoch window, which feeds a staging head and a respiratory head; the respiratory head also reads the cardiorespiratory embedding directly, and the AHI is computed from the respiratory scores over decoded sleep.

Figure 3: An illustrative held-out night (patient SN90, three-seed MM-Net, staging accuracy $0.83$ ). (A) Predicted and reference hypnograms, REM highlighted. (B) EEG spectrogram, C4 derivation, $0$ – $25$ Hz. (C) Per-epoch stage-probability ribbon; the black line is the maximum posterior.

Figure 4: Row-normalized confusion matrix for MM-Net (three-seed, pooled ten-fold test epochs, hidden-Markov operating point). Errors concentrate on N1, which is absorbed into Wake and N2.

Model	W $\uparrow$	N1 $\uparrow$	N2 $\uparrow$	N3 $\uparrow$	R $\uparrow$
MM-Net	0.81	0.20	0.82	0.72	0.79

Table 5: Per-class staging F1 (Wake, N1, N2, N3, REM), ten-fold patient-independent, at the hidden-Markov operating point (MM-Net: three-seed, pooled test epochs).

Figure 5: Per-fold staging accuracy of MM-Net with the sleep-adapted encoder, relative to the frozen-encoder reference (three-seed, ten patient-independent folds). The training embeddings are cross-fitted in both cases; aligning them to the deployed encoder turns an inconsistent effect into a gain in eight folds of ten.

Figure 6: t-SNE [ 48 ] of

4000

epochs from the ten held-out patients of one fold, colored by scored stage. Left: frozen LaBraM. Right: the sleep-adapted, aligned EEG/EOG encoder used in MM-Net.

Figure 7: Respiratory-event detection by MM-Net (three-seed), pooled over the ten patient-independent test folds. (a) ROC curve. (b) Precision–recall; the dashed line is the

0.160

event prevalence, the no-skill floor.

(a) Detection method
Method	AUC $\uparrow$	AP $\uparrow$
Desaturation rule	0.595	0.207
Logistic regression	0.603	0.211
Gradient boosting	0.673	0.290
Raw effort belt § [ 33 ]	0.602	0.252
Raw seven channels §	0.733	0.366

Table 7: Respiratory-event detection on iSLEEPS. (A) Comparison with classical and raw-signal baselines on the same folds ( § single seed) and (B) MM-Net AUC by respiratory-event type. Bold denotes the best value in each comparison.

Modality removed	Output	Change	Holm $p$
EEG (neural)	Staging accuracy	$-0.050$	$0.018$
All cardiorespiratory	Respiratory AUC	$-0.118$	$0.018$
Respiratory effort	Respiratory AUC	$-0.028$	$0.031$
Airflow	Respiratory AUC	$-0.004$	$0.65$

Table 9: Modality removal and retraining (frozen-encoder configuration; ten folds, three seeds). Each row removes one modality and reports the change in the output that modality serves, relative to the full configuration (staging accuracy

0.736

, respiratory AUC

0.796

). Holm

p

: Wilcoxon on the ten fold means, Holm-corrected across the nine ablations of the grid.

Figure 8: MM-Net AHI estimate against the annotated AHI. Left: iSLEEPS, ten-fold test patients. Right: ISRUC-I, MM-Net trained on iSLEEPS only and applied without retraining (Section 5.10 ). Shading marks the AASM severity bands; the dashed line is identity.

AHI band	AHI (events/h)	Patients	Staging acc $\uparrow$
Normal	$<5$	15	$0.784\pm 0.057$
Mild	$5$ – $15$	23	$0.754\pm 0.092$
Moderate	$15$ – $30$	23	$0.764\pm 0.083$
Severe	$\geq 30$	38	$0.758\pm 0.078$

Table 11: Sleep-staging accuracy of MM-Net across AASM severity groups of the clinical AHI in iSLEEPS. Values are mean

\pm

SD across patients; the ordered-group trend is not significant (Jonckheere–Terpstra

p=0.20

Characteristic	Group	Patients	Staging acc $\uparrow$	Encoder gain
NIHSS	$0$ – $4$ (minor)	86	$0.758$	$+0.004$
	$\geq 5$ (moderate to severe)	12	$0.778$	$+0.028$
Modified Rankin	$0$ – $2$ (independent)	88	$0.757$	$+0.005$
	$3$ – $5$ (dependent)	10	$0.794$	$+0.024$

Table 12: Sleep-staging accuracy of MM-Net (three-seed, per patient) by stroke severity (NIHSS) and functional status (modified Rankin scale) in iSLEEPS. Encoder gain: accuracy difference from the frozen-encoder reference of Table 6 on the same patients.

Sleep Stage Classification

Sleep stage classification assigns sleep epochs to physiological stages from signals such as EEG, helping quantify sleep architecture and support clinical monitoring.

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Accurate sleep staging is essential for diagnosing OSA and hypopnea in stroke patients. Although PSG is reliable, it is costly, labor-intensive, and manually scored. While deep learning enables automated EEG-based sleep staging in healthy subjects, our analysis shows poor generalization to clinical populations with disrupted sleep. Using Grad-CAM interpretations, we systematically demonstrate this limitation. We introduce iSLEEPS, a newly clinically annotated ischemic stroke dataset (to be publicly released), and evaluate a SE-ResNet plus bidirectional LSTM model for single-channel EEG sleep staging. As expected, cross-domain performance between healthy and diseased subjects is poor. Attention visualizations, supported by clinical expert feedback, show the model focuses on physiologically uninformative EEG regions in patient data. Statistical and computational analyses further confirm significant sleep architecture differences between healthy and ischemic stroke cohorts, highlighting the need for subject-aware or disease-specific models with clinical validation before deployment. A summary of the paper and the code is available at https://himalayansaswatabose.github.io/iSLEEPS_Explainability.github.io/

Abstract

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