A randomised controlled trial of physical activity and cognitive training in older adults: the PhABHeaD study.

Background: Robust empirical evidence supports the effectiveness of physical and cognitive training in preventing and delaying cognitive decline. Emerging research suggests distinct neurobiological mechanisms underpin the effects of these different training modalities. An unresolved question is whether the mechanisms through which these training modalities impart their effect interact synergistically to improve cognitive outcomes, rather than exerting additive effects, differ. In addition, past research has been inconsistent in adequately controlling for or documenting the dosage of physical and/or cognitive training. Consequently, the aim of this study is to assess the relative effectiveness of physical and cognitive training conducted in isolation or concurrently, whilst rigorously controlling and documenting the treatment parameters.

Methods: This study is a three-arm randomised controlled trial conducted over a 3-month period, comparing cognitive training, physical activity, and a combination of both interventions. Older cognitively healthy participants (n = 126) aged 60-75 years will be recruited from the community. The physical only training will require participants to cycle on a cycle ergometer at above 60% of their age-predicted heart rate maximum for 50 min with a 3-min warm-up and cool-down period. The cognitive only training will require participants to complete up to five different cognitive tasks selected from a set of eight on the BrainHQ platform during each 50-min training session. The concurrent cognitive and physical training will require participants to undertake both treatments at the same time. Primary outcomes, assessed pre- and post- intervention, will include speed of processing and episodic memory assessed with the NIH Toolbox, as well as general driving skills assessed on a driving simulator.

Discussion: Findings will inform the design of interventions and population health advice aimed at mitigating cognitive decline. If a substantial synergetic effect is detected, it may lead to the use of more widespread concurrent physical and cognitive training and the potential development of methods to make concurrent training practical. Findings will also provide important clarification as to the relative benefit of the two modes of training.

Trial registration: Prospective registration with Australia and New Zealand Clinical Trial Registry (ACTRN12624001088538) on 10th September 2024 and World Health Organisation International Clinical Trials Registry (U1111-1280-3851).