Dual-Task Versus Combined Exercise Training in Older Adults With Type 2 Diabetes

Older adults with type 2 diabetes mellitus (T2DM) may experience balance, gait, and cognitive impairments. T2DM is associated with an increased risk of cognitive decline and dementia in older adults. Factors such as insulin resistance, impaired glucose metabolism, advanced glycation end-products, impaired amyloid beta clearance, oxidative stress, and inflammation may contribute to these changes. T2DM has been linked to impairments in episodic memory, verbal fluency, working memory, processing speed, and executive functions. Executive functions are higher-level processes that oversee and regulate other cognitive functions. These capabilities support planning, decision-making, switching between tasks, goal-directed behavior, and coordinating simultaneous activities. Executive function also contributes to the integration of sensory information required for balance and gait. Impairments in these functions may therefore compromise functional mobility and increase fall risk in older adults with T2DM.

Dual-task paradigms are used to examine performance when two tasks are undertaken simultaneously. A primary motor task, such as walking, is combined with a secondary task, and the effects on performance are evaluated. Everyday activities, such as walking while talking, frequently involve these simultaneous demands. When the combined demands of the tasks exceed available attentional resources, performance on one or both tasks may deteriorate. Executive dysfunction may increase this interference. Dual tasks can involve motor-cognitive, cognitive-cognitive, or motor-motor combinations. Previous research has reported adverse effects of dual-task conditions on gait parameters in individuals with T2DM. These findings highlight the importance of considering the interaction between cognitive abilities and motor skills when planning rehabilitation programs.

The effects of dual-task training on balance and cognitive function have been investigated in other populations at increased risk of falls, including stroke survivors, individuals with Parkinson's disease, and older adults with a history of falls. Because cognitive processes contribute to balance and mobility, evaluating physical performance together with cognitive function may provide a more comprehensive understanding of the effects of dual-task training. Previous studies have reported improvements in balance and executive function following dual-task training in older adults. Combined aerobic and resistance exercise has also shown potential benefits for cognition in individuals with T2DM. However, whether adding concurrent cognitive tasks to a combined exercise program provides additional benefits in older adults with T2DM remains unclear.

Brain-derived neurotrophic factor (BDNF) is involved in synaptic plasticity and may provide a biological link between exercise and cognitive function. Nevertheless, reported BDNF responses to exercise in individuals with T2DM have been variable. Assessing serum BDNF alongside functional and cognitive outcomes may help characterize the responses to combined physical and cognitive training, although serum measurements alone cannot establish changes in brain function.

This three-arm randomized controlled study will investigate the effects of dual-task training compared with combined exercise training and a control condition in adults aged 65 years and older with T2DM. Participants will be randomly assigned to the dual-task training group, the combined exercise training group, or the control group. Both exercise groups will undergo aerobic, resistance, and balance training three times per week for eight weeks. The dual-task group will perform the same physical exercise program with concurrent cognitive tasks targeting memory, verbal fluency, executive function, mental arithmetic, and divided attention. The combined exercise group will perform the physical exercises without concurrent cognitive tasks. The control group will receive standardized education on physical activity, glycemic self-monitoring, and reducing sedentary behavior, with weekly telephone contact.

The study will examine whether adding concurrent cognitive tasks to combined exercise training provides additional benefits for functional mobility, assessed using the Timed Up and Go test. Exercise capacity, global cognitive function, executive function, reaction time, dual-task mobility and cost, diabetes-specific quality of life, and serum BDNF levels will also be evaluated before and after the intervention. The study aims to clarify the potential contribution of concurrent cognitive training to rehabilitation in older adults with T2DM.

Inclusion criteria

• Being followed up with a diagnosis of Type 2 Diabetes Mellitus for at least 6 months (fasting plasma glucose of 7.0 mmol/L or higher)
• Not having participated in any structured exercise program for at least 6 months prior.
• Being willing to volunteer for the study

Exclusion criteria

• Nephropathy
• Retinopathy
• Having dementia or Alzheimer's disease
• Using a walking aid
• Having ulceration
• Using balance-curing drugs
• Surviving myocardial infarction at least 6 months ago
• Stable or unstable angina pectoris
• Left ventricular ejection fraction below 40%
• Peripheral arterial diseases
• Resting blood pressure above 160/100 mmHg
• Body mass index above 35 kg/m2
• Having a history of deep vein thrombosis, pulmonary embolism or stroke in the past