THE EFFECT OF VISUAL DEPRIVATION DURING COGNITIVE MOTOR DUAL TASK TRAINING ON COGNITIVE FUNCTION IN TYPE 2 DIABETES MELLITUS

Introduction

Diabetes mellitus comprises a group of chronic metabolic illnesses distinguished as high blood glucose levels resulting from deficiencies in insulin secretion, insulin action, or both.¹ Unlike type 1 diabetes mellitus (T1DM), which is an autoimmune disorder marked by the destruction of insulin-producing beta cells, type 2 diabetes mellitus (T2DM) primarily arises due to insulin resistance along with varying degrees of insulin deficiency.² The World Health Organization (WHO) estimated that 422 million people worldwide had diabetes in 2014. Nearly four million fatalities annually are attributed to high blood sugar.³ By 2045, there will be at least 629 million diabetics worldwide. As per the International Diabetes Federation (IDF), 850 billion US dollars were spent on adult diabetes-related medical treatment worldwide in 2017. In India, the prevalence of T2DM is rapidly increasing, with significant public health implications.^4,5

Type 2 diabetes is not only a metabolic disorder but also a significant risk factor for cognitive decline and dementia.^6–9 The mechanistic pathways include hyperphosphorylation of tau proteins, which links insulin dysregulation with Alzheimer’s disease pathology.^10–13 Chronic accumulation of advanced glycation end products (AGEs) due to sustained hyperglycemia,⁷ and endothelial dysfunction causing microvascular damage, neurovascular uncoupling, and reduced cerebral blood flow.^7–9,14 These pathologies accelerate deterioration in domains such as verbal fluency, executive function, processing speed, memory, and overall cognition.¹⁴

Interventions for cognitive impairment in T2DM commonly employ resistance and aerobic training, which improve insulin sensitivity, cardiorespiratory fitness, and hippocampal integrity, thus benefiting cognitive function.^13,15–19 Multi-modal programs combining physical and cognitive training have demonstrated superior improvements.^{13,15–18,20} Among these, cognitive-motor dual-task training (CMDT)—involving simultaneous performance of cognitive and motor tasks—capitalizes on synergistic neuroplastic mechanisms, yielding greater cognitive benefits compared to single-modality approaches.^21–23 In CMDT, performing simultaneous cognitive and motor tasks challenges attentional control and postural stability, contributing to improvements in motor-cognitive interference management during walking and balance.^24,25 This aligns with the guided plasticity facilitation framework, which posits that concurrent physical and cognitive stimulation enhances neuroplasticity via factors like increased brain-derived neurotrophic factor (BDNF).²⁰

However, a critical research gap exists regarding the role of visual deprivation during CMDT for T2DM populations. While CMDBT enhances functional connectivity in motor-cognitive brain regions and improves cerebral cortex activation,^26–28 it remains unclear whether removing visual input through blindfolding could further augment neuroplasticity and cognitive outcomes. Visual deprivation via blindfolding functions through sensory substitution, whereby information is rerouted via alternate senses such as tactile and proprioceptive pathways to the visual cortex, promoting cross-modal neuroplasticity.²⁹ Sensory substitution, first introduced by Paul Bach-y-Rita,³⁰ has demonstrated efficacy in cortical reorganization and perceptual compensation particularly among visually impaired individuals.^31,32

Given that individuals with T2DM experience metabolic and microvascular impairments compromising neural plasticity,^32–34 blindfold training may uniquely amplify compensatory brain activation and multisensory integration in this population. By forcing dependence on non-visual sensory modalities, blindfold cognitive-motor dual-task training may serve as a stronger neuroplastic stimulus than training allowing visual input.

The research question for this study is: Does incorporating visual deprivation (blindfolding) into cognitive-motor dual-task training (CMDBT) produce superior improvements in cognitive function among adults with type 2 diabetes mellitus compared to standard conventional therapy involving aerobic and resistance training? The primary aim is to evaluate the effect of cognitive-motor blindfold training on cognitive function in individuals with type 2 diabetes mellitus.

The objective is to compare the effects of CMDBT and standard conventional therapy employing aerobic and resistance training on multiple cognitive domains including memory, executive function, attention, and processing speed, as well as to elucidate neurophysiological mechanisms underlying potential cognitive benefits. Cognitive-Motor Blindfold Training entails simultaneous motor and cognitive tasks performed under enforced visual deprivation via blindfolding.^30–32

Unlike standard conventional therapy, which involves aerobic and resistance training without integrated cognitive tasks or sensory deprivation, CMDBT promotes reliance on proprioceptive, tactile, and vestibular inputs, thereby enhancing multisensory integration and cross-modal plasticity. Physiologically, CMDBT is hypothesized to strengthen alternative neural pathways, stimulate cortical reorganization especially in prefrontal and parietal networks, and increase demands on compensatory processing mechanisms, resulting in superior cognitive resilience.^32–34 This study tested the hypothesis that CMDBT, with its added component of visual deprivation during dual-task training, led to significantly greater improvements in cognitive function than standard conventional therapy of aerobic and resistance training in individuals with T2DM by leveraging enhanced neuroplasticity induced through sensory deprivation and multisensory reweighting.

Method

Based on the literature, cognitive motor dual-task blindfold training has been applied in cognitive studies, but there is insufficient evidence regarding its use in individuals with type 2 diabetes mellitus (T2DM). This study was approved by the Institutional Ethics Committee of Apollo Institute of Medical Science and Research, Chittoor, Andhra Pradesh, India, on 30-12-2023 (Ethics Committee Number: PG/35/IEC/AIMSR/2023). All participants provided written informed consent prior to enrollment.

Study design: This was a single-blinded, randomized controlled trial (RCT) conducted according to CONSORT guidelines (Clinical Trials Registry of India, CTRI/2024/01/061956). The study population included patients diagnosed with T2DM attending the physiotherapy outpatient department at Apollo District Headquarters Hospital, Murukambattu, Chittoor, Andhra Pradesh, India. Participants were selected through purposive sampling to meet inclusion criteria and were randomly allocated to two groups using a lottery method to ensure unbiased assignment.

Participant flow

A total of 182 participants were assessed for eligibility. Of these, 120 were excluded due to not meeting inclusion criteria or declining to participate. The remaining 62 eligible participants were randomized equally into two groups: Group A (Cognitive-Motor Dual-Task Blindfold Training, CMDBT; n = 31) and Group B (Control: Moderate-Intensity Aerobic and Resistance Training; n = 31). All participants in both groups received their allocated interventions and completed the study protocol. There were no dropouts and follow-up. Data from all 62 participants were analyzed on an intention-to-treat basis. The CONSORT Flow Diagram illustrating participant enrollment, allocation, follow-up, and analysis in Figure 1.

Figure 1. CONSORT flow diagram illustrating the recruitment, randomization, allocation to Cognitive-Motor Dual-Task Blindfold Training (CMDBT) and control (conventional aerobic-resistance therapy) groups, participant follow-up, and inclusion in the analysis of cognitive function outcomes in adults with type 2 diabetes mellitus.

Results

A total of 62 participants diagnosed with type 2 diabetes mellitus were randomly allocated into two groups: Group A (Cognitive-Motor Dual-Task Blindfold Training, CMDBT; n = 31) and Group B (Control: Moderate-Intensity Aerobic and Resistance Training; n = 31). Baseline demographic and clinical characteristics were comparable between groups, with no statistically significant differences observed in age, gender distribution, duration of diabetes, educational level, HbA1c, body mass index (BMI), or Mini-Mental State Examination (MMSE) scores (all p > 0.05), confirming homogeneity.³⁷ The normality of Montreal Cognitive Assessment (MoCA) scores was verified using the Shapiro-Wilk test (p > 0.05), allowing the use of parametric statistical analyses. There were no dropouts during the intervention period, and all participants completed baseline and post-intervention assessments. Data were analyzed on an intention-to-treat basis.

Within-group analyses showed significant improvements in cognitive function for both groups. In Group A (CMDBT), mean MoCA scores increased by 3.32 points, from 25.81 ± 1.74 pre-intervention to 29.13 ± 0.76 post-intervention (t = 6.32, df = 30, p < 0.0001). This increase exceeded the minimal clinically important difference (MCID) of 2.3 points and was accompanied by a 56% reduction in score variability (SD reduced from 1.74 to 0.76), indicating a consistent and robust treatment effect (Table 1, Figure 2). In contrast, Group B (control) exhibited a statistically significant but smaller mean increase of 0.94 points in MoCA scores, from 25.77 ± 1.45 to 26.71 ± 1.37 (t = 6.02, df = 30, p = 0.0006). However, this gain did not surpass the MCID threshold. The standard deviation decreased marginally by about 5.5% (from 1.45 to 1.37), suggesting more variability in response to aerobic and resistance training alone (Table 2, Figure 3).

Figure 2. Graphical representation of Means of pre and post values of MoCA within experimental Group A.

Figure 3. Graphical representation of Means of pre and post values of MoCA within CONTROL Group B.

Between-group comparison demonstrated that post-intervention MoCA scores in Group A (29.13 ± 0.76) were significantly higher than in Group B (26.71 ± 1.37), with a mean difference of 2.42 points (p < 0.0001) (see Table 3). Effect size analysis showed a large effect for Group A (Cohen’s d = 1.89) versus a moderate effect for Group B (d = 0.65) (Figure 3), further supporting the superior cognitive benefits of the blindfolded cognitive-motor dual-task training (Table 3, Figure 4).

Figure 4. Graphical representation of Means of post values of MoCA between Group A & Group B.

Clinically, the magnitude of improvement in Group A aligns with thresholds associated with reduced dementia risk in diabetic populations, highlighting the potential of integrating sensory deprivation to augment cognitive rehabilitation in type 2 diabetes mellitus.

These findings advocate for incorporating sensory-enhanced cognitive-motor dual-task training into rehabilitation protocols to optimize cognitive outcomes and potentially mitigate diabetes-associated cognitive decline.

Discussion

This study demonstrated that cognitive-motor dual-task blindfold training (CMDBT) combined with moderate-intensity aerobic and resistance exercises significantly improved cognitive function in individuals with type 2 diabetes mellitus (T2DM). Both intervention groups exhibited statistically significant cognitive gains before and after intervention (p < 0.0001), but participants receiving CMDBT showed significantly greater improvement compared to those undergoing conventional therapy alone. These results highlight the differential impact of multimodal cognitive-motor interventions versus standard exercise protocols on cognitive outcomes in T2DM.

Cognitive decline in T2DM is multifactorial, with vascular dysfunction playing a critical role. Elevated blood glucose leads to protein accumulation on vascular walls, causing damage to endothelial cells and reducing synthesis of vasodilating substances like nitric oxide, while promoting reactive oxygen species generation and oxidative stress. This pathophysiological cascade impairs cerebral blood flow, resulting in neurovascular uncoupling and neuronal injury. Such mechanisms accelerate deterioration in cognitive domains including global cognition, executive function, processing speed, verbal fluency, and memory. This mechanistic explanation is supported by recent literature and clearly distinguishes pathological processes from study results.

The cognitive benefits observed in the CMDBT group are likely attributable to enhanced functional connectivity between motor and cognitive brain regions induced by dual-task training. Such training has the potential to improve gait and other motor functions while simultaneously promoting brain activation and neuroplasticity through complex neural circuit engagement. Walking, as a motor behavior, integrates sensory inputs processed by the brain, cerebellum, and brainstem, making it an ideal target for dual-task interventions. The addition of blindfolding enforces sensory substitution by rerouting non-visual information through the visual cortex, thereby enhancing cross-modal neuronal plasticity and interhemispheric communication. These mechanisms align with findings from sensory substitution research demonstrating cortical reorganization beneficial in both visually impaired individuals and those undergoing cognitive rehabilitation.

Eggenberger et al. (2015) studied older adults (≥70 years) using combined cognitive and physical training modalities, including verbal memory tasks paired with treadmill walking and virtual reality dancing.³⁵ Utilizing standardized cognitive assessments such as the Digit Symbol Substitution Task and Trail Making Test Part B, they found that cognitive-physical dual-task training significantly improved working memory, executive functioning, and attention switching—especially with longer intervention durations. Our findings align with Eggenberger et al., reinforcing the concept that simultaneous cognitive and physical tasks can confer additive cognitive benefits in populations at risk for decline.³⁵

Similarly, Hewston et al. (2013) investigated dual-task effects on gait performance in adults aged 65 and older with T2DM, reporting slower gait speeds in diabetic participants compared to healthy controls.³⁶ Their findings showed that dual-task training improved gait performance in diabetics, suggesting enhanced motor function. Although Hewston et al. focused primarily on motor outcomes, their results provide indirect support for the neurological benefit of dual-task approaches, consistent with the cognitive improvements observed here with CMDBT. The superior cognitive improvements demonstrated by the CMDBT group in this study are consistent with previous literature on multimodal and dual-task interventions. Notably, Eggenberger et al. (2015)³⁵ found that multicomponent physical exercise programs incorporating simultaneous cognitive training yielded significantly greater cognitive benefits for older adults compared to programs that included only physical exercise. Similarly, Hewston and Deshpande (2013)³⁶ reported that dual-task balance training improved gait parameters and reduced cognitive-motor interference among older adults with type 2 diabetes mellitus. These findings complement the current study by emphasizing the value of interventions that actively engage both cognitive and motor domains to enhance neuroplasticity and functional outcomes in clinical populations. Our results expand on this evidence, further suggesting that integrating visual deprivation into cognitive-motor dual-task training may amplify neuroplasticity and cognitive resilience, particularly in those with T2DM, by stimulating compensatory and multisensory neural pathways.

This study advances the literature by incorporating blindfold-induced sensory deprivation into cognitive-motor dual-task training, a novel approach that appears to potentiate neuroplasticity beyond conventional dual-task protocols. The structured 30-minute CMDBT sessions, combined with 30 minutes of moderate-intensity aerobic and resistance training, demonstrated feasibility, time-efficiency, and cost-effectiveness, making it well-suited for inpatient rehabilitation settings. Compared to conventional therapy, the significantly superior cognitive gains observed in the CMDBT group emphasize the value of sensory substitution strategies as critical adjuncts to optimize cognitive rehabilitation in T2DM.

Given these findings, we strongly recommend including CMDBT in clinical practice for managing cognitive decline associated with type 2 diabetes. Future research should explore long-term cognitive and functional outcomes, dose-response relationships, and underlying neurophysiological mechanisms using modalities such as neuroimaging or biomarker analyses.

Conclusion

This study demonstrated that a 12-week cognitive-motor dual-task training (CMDBT) program, combined with aerobic and resistance exercises, produced significant and clinically meaningful improvements in cognitive function among individuals with type 2 diabetes mellitus (T2DM). While both CMDBT and moderate-intensity aerobic exercise interventions yielded significant within-group cognitive gains, CMDBT resulted in significantly greater enhancements compared to aerobic training alone. These findings highlight CMDBT’s potential as an effective, feasible, and time-efficient intervention to mitigate cognitive decline associated with T2DM. The robust improvements observed provide a strong rationale for integrating CMDBT into clinical rehabilitation protocols and warrant further research to explore its long-term benefits and underlying neurophysiological mechanisms. Ultimately, such interventions may contribute to improving cognitive health and overall quality of life in patients living with T2DM.

Ethics and consent statement

This study was conducted in accordance with the Declaration of Helsinki and was approved by an institutional ethics committee on 30-12-2023 at the Apollo Institute of Medical Science and Research, Chittoor, Andhra Pradesh, India. Ethics Committee Number: PG/35/IEC/AIMSR/2023. Written informed consent was obtained from all participants. The study conducted as per guideline of Declaration of Helsinki.