Optimizing Combined Physical and Cognitive Activity in Community-Dwelling Older Adults.

Recognizing the escalating dementia rates, its profound social and economic consequences and the lack of curative treatments, the World Health Organization (WHO) emphasizes the importance of reducing modifiable risk factors for dementia, as outlined in Action Area 3 of the WHO Global action plan on the public health response to dementia 2017-2025. Previous research suggests that combining physical activity and cognitive activity may produce greater cognitive benefits than either activity alone, but it remains unclear which specific combinations are most effective in older adults. In particular, little is known about how physical activity intensity and cognitive activity difficulty interact, and whether cardiorespiratory fitness influences these effects. The present study addresses this knowledge gap in community-dwelling older adults.

The study is conducted in two consecutive parts. In the preparatory phase, participants attend one laboratory visit. During this phase, baseline screening and descriptive assessments will be performed, cardiorespiratory fitness will beestimated using the 6-Minute Walk Test, individualized physical activity intensity zones will be determined using heart-rate reserve, and cognitive activities will be classified as easy or challenging based on subjective ratings. Participants will also be familiarized with treadmill walking and simultaneous physical and cognitive task performance.

In the fundamental phase, eligible participants will complete four laboratory sessions in randomized order, each involving one combination of physical and cognitive activity: light physical activity with easy cognitive activity, light physical activity with challenging cognitive activity, moderate physical activity with easy cognitive activity, and moderate physical activity with challenging cognitive activity. During each session, participants walk on a treadmill at a prescribed heart-rate-based intensity while simultaneously performing cognitive tasks. Cognitive functioning is assessed immediately before and after each session using three tasks from the CANTAB neuropsychological test battery: a) Multitasking test (MTT), (b) Delayed Matching to Sample (DMS), and (c) Match to Sample Visual Search (MTS), allowing the study to examine the short-term cognitive effects of each physical activity × cognitive activity combination. The overall aim is to identify the optimal combination of simultaneous physical and cognitive activity for acute cognitive benefits in older adults.

• Light physical activity + easy cognitive activity (Behavioral): Participants walk on a treadmill at an individualized light physical activity intensity (30-39% of heart rate reserve) while performing cognitive tasks individually classified as easy.
• Light physical activity + challenging cognitive activity (Behavioral): Participants walk on a treadmill at an individualized light physical activity intensity (30-39% of heart rate reserve) while performing cognitive tasks individually classified as challenging.
• Moderate physical activity + easy cognitive activity (Behavioral): Participants walk on a treadmill at an individualized moderate physical activity intensity (40-59% of heart rate reserve) while performing cognitive tasks individually classified as easy.
• Moderate physical activity + challenging cognitive activity (Behavioral): Participants walk on a treadmill at an individualized moderate physical activity intensity (40-59% of heart rate reserve) while performing cognitive tasks individually classified as challenging.

Primary outcomes

• Change in Multitasking Test (MTT) performance from pre- to post-condition [Immediately before and 10 minutes after each experimental condition]: Change in accuracy and response latency from pre- to post-condition on the Multitasking Test (MTT), assessing executive functioning, cognitive flexibility, and processing speed.
• Change in Delayed Matching to Sample (DMS) performance from pre- to post-condition [Immediately before and 10 minutes after each experimental condition]: Change in accuracy and response latency from pre- to post-condition on the Delayed Matching to Sample (DMS), assessing short-term visual recognition memory.
• Change in Match to Sample Visual Search (MTS) performance from pre- to post-condition [Immediately before and 10 minutes after each experimental condition]: Change in accuracy and response latency from pre- to post-condition on the Match to Sample Visual Search (MTS), assessing visual attention and psychomotor speed.

Secondary outcomes

• General impression of each experimental condition [Immediately after each experimental condition, during the 10-minute post-condition interval.]: Self-reported general impression of each experimental condition, rated on a 0-10 scale, where 0 indicates "not good at all" and 10 indicates "very good."
• Perceived feasibility of each experimental condition [Immediately after each experimental condition, during the 10-minute post-condition interval.]: Self-reported feasibility of each experimental condition, rated on a 0-10 scale in response to the statement "I feel capable of doing this session," where higher scores indicate greater perceived feasibility.
• Enjoyment of each experimental condition [Immediately after each experimental condition, during the 10-minute post-condition interval.]: Self-reported enjoyment of each experimental condition, rated on a 0-10 scale in response to the statement "I enjoyed this session," where higher scores indicate greater enjoyment.

Sex: All, ages: 65 Years to any

Inclusion Criteria:

* Aged 65 years or older
* Community-dwelling
* Able to safely walk on a treadmill and complete the 6-Minute Walk Test
* Sufficient Dutch proficiency to understand study instructions and complete study procedures

Exclusion Criteria:

* MoCA score < 23
* Severe cognitive or physical impairment that would hinder participation or understanding of study procedures
* Use of medication affecting heart rate
* Any medical condition contraindicating engagement in physical or cognitive activity
* Severe visual or hearing impairment that would prevent valid participation in the study procedures

• Greet Cardon, Prof. Dr., Principal investigator, University Ghent