Cognitive Decline: A Window of Opportunity for Reducing the Risk of Dementia?

Abstract

The number of people living with dementia is expected to almost double in the next 10 years and more than triple in the next 30 years. Lifestyle risk factors such as obesity, physical inactivity and social isolation are estimated to cause more than 35% of dementia cases worldwide. One of the highest risk groups for developing dementia are those experiencing cognitive decline, such as subjective cognitive decline and mild cognitive impairment. Hence, there is a pressing need to develop interventions to reduce risk, especially for these high risk groups. In the short- to medium-term, a significant proportion of people with cognitive decline can experience a spontaneous improvement in cognition. There is also preliminary evidence that interventions can be beneficial for this group, though this strategy has not been robustly tested. It has been hypothesised that during the cognitive decline period preceding dementia, the brain retains sufficient neuroplasticity that it is possible to modify the trajectory of decline. The thesis explores the outcomes from a multidomain dementia risk reduction intervention for people experiencing cognitive decline, the Body, Brain, Life, for Cognitive Decline (BBL-CD) intervention. The intervention is a proof-of-concept trial that adapts a previously successful primary risk reduction trial to a secondary risk reduction intervention. The thesis is comprised of four publications: First, a protocol paper sets out the rationale, methods and analyses that were conducted. This publication details the evidence for choosing the domains of Mediterranean diet, physical activity, and cognitive engagement. It explains the educational modules the control and intervention groups complete, and the additional activities only undertaken by the intervention group. Second, the primary outcome measures of this thesis were lifestyle risk for Alzheimer's disease and cognition. This paper demonstrated that the intervention group were able to significantly improve overall lifestyle risk and cognition relative to the control group, which showed little change in either outcome measure. Third, the feasibility of the intervention in this participant group was tested using three elements of the Bowen Feasibility Framework: Acceptability, implementation, and efficacy to change lifestyle behaviours. The intervention was found to be highly acceptable, was mostly implemented successfully, and mostly demonstrated efficacy to change lifestyle behaviours. While the intervention was found to be feasible, some major learnings and improvements were identified for future interventions. Finally, a fourth paper examined the potential health-related quality of life outcomes of the intervention. The intervention did not show a significant group x timepoint interaction, required to demonstrate efficacy. However, the presence of several significant between- and within-group differences and the magnitude of these differences (>3 points on SF-36) are reported as potential outcomes of interest in larger, more adequately powered studies in this participant group in the future. Together, these publications combine to form a thesis that lends support to the notion that secondary dementia risk reduction interventions are both feasible and show efficacy. The results support the conduct of larger, longer study to characterise any improvements in lifestyle and cognition more accurately and determine whether these improvements are sustainable long term. This thesis provides proof-of-concept that the cognitive decline period represents a window of opportunity to reduce lifestyle dementia risk and warrants further long-term investigation. Show more