Basic Characteristics
A total of 1,200 participants were included in this study, comprising 942 individuals in the healthy cohort and 258 individuals in the insomnia cohort. For the brain age prediction module, the training set consisted of 753 participants, and the validation set included 189 participants. For the brain age gap analysis module, the healthy cohort corresponded to the validation set from the prediction module, while the insomnia cohort consisted of 258 participants. The mean age of the insomnia cohort was 52.90 years (range: 15–78), and the mean age of the healthy cohort was 46.54 years (range: 12–86.31).
Performance of Brain Age Prediction Model and Contribution of Multimodal Fusion
To evaluate the impact of different MRI modalities on brain age prediction performance, the model inputs were separately defined as radiomics features extracted from T1-weighted images, from T2-weighted images, and from a fusion of T1 and T2 features.
As shown in Fig. 1, the predictive performance of single-modality models varied. The T1-based model achieved a mean absolute error (MAE) of 7.58 years, a root mean square error (RMSE) of 9.67 years, and a coefficient of determination (R²) of 0.57, indicating a relatively good degree of fit. In contrast, the T2-based model yielded an MAE of 7.90 years, an RMSE of 10.36 years, and an R² of 0.51, suggesting slightly lower prediction accuracy and a reduced fit compared to the T1 model.
When features from both T1 and T2 modalities were fused, multimodal integration produced a marked improvement in predictive performance. The MAE decreased to 6.42 years, RMSE was reduced to 8.37 years, and R² increased to 0.68, demonstrating clear optimization in both error reduction and explanatory power. These results indicate that the feature information carried by T1 and T2 modalities is complementary: T1 is sensitive to structural integrity and gray matter morphology, whereas T2 is more responsive to tissue water content and white matter alterations. Their fusion provides a more comprehensive representation of brain characteristics, thereby enhancing the model’s capacity to capture individual differences in brain age.
Brain Age Gap and Accelerated Aging in Insomnia: Correlation, Age-Related Bias, and Group Comparisons
As illustrated in Fig. 2A, the proposed brain age prediction model successfully captured the age-related trends in structural brain changes. Predicted Brain Age showed a significant positive correlation with Chronological Age, with data points from both groups distributed roughly along the diagonal line. Notably, in the insomnia group (red), most data points were located above the diagonal, indicating that the predicted brain age was substantially greater than the chronological age, reflecting a clear pattern of advanced brain aging.
To further investigate this phenomenon, the Brain Age Gap (BAG = Predicted Age − Chronological Age) was calculated and its relationship with chronological age was examined. As shown in Fig. 2B, the raw BAG was significantly and positively correlated with chronological age (r = 0.599, p < 0.001), suggesting a systematic overestimation in older individuals—an age-related bias in the model. To eliminate the confounding effects of this bias on between-group comparisons, BAG was adjusted for age using a linear regression model. The results after adjustment are presented in Fig. 2C and Table 1. The insomnia group exhibited a markedly higher predicted brain age compared to chronological age (uncorrected mean BAG = 8.10 years; age-adjusted mean BAG = 1.60 years; both p < 0.001), indicating a pronounced trend of advanced brain aging and accelerated decline. In the healthy control group, the magnitude of BAG was smaller (uncorrected mean = 1.26 years, p = 0.038), and after age adjustment the mean BAG was slightly lower than the chronological age (− 2.18 years, p = 0.038). Between-group comparisons confirmed that BAG in the insomnia cohort was significantly greater than in healthy controls both before (difference ≈ 6.84 years, p < 0.00001) and after adjustment (difference ≈ 3.78 years, p < 0.00001).
Furthermore, Fig. 2D depicts the distribution of age-adjusted BAG in both groups. The curve for the insomnia group is shifted to the right, with a peak noticeably higher than that of healthy controls and concentrated within the positive BAG range. This distribution pattern aligns with the mean comparison results and visually supports the conclusion that most individuals in the insomnia group have a predicted brain age substantially exceeding their chronological age.
In summary, patients with insomnia not only exhibited a larger BAG than healthy individuals but also maintained significantly elevated predicted brain age even after removing age-related bias. These findings suggest that insomnia may be closely linked to accelerated brain aging, with structural brain characteristics potentially reflecting an earlier and steeper trajectory of decline.
Table 1
Brain Age Gap and Age-Adjusted BAG in Healthy and Insomnia Cohorts.
| | n | Brain Age Gap | Age-corrected Brain Age Gap | r |
|---|
Mean | SD | Mean | SD | |
|---|
Normal Cohort | 189 | 1.26 | 8.3 | -2.18 | 7.75 | 0.599(p < 0.001) |
Insomnia Cohort | 258 | 8.1 | 8.57 | 1.6 | 6.49 | |