Pathways of Prevention: A Scoping Review of Dietary and Exercise Interventions for Neurocognition

Abstract

Alzheimer's disease and related dementias (ADRD) represent an increasingly urgent public health concern, with an increasing number of baby boomers now at risk. Due to a lack of efficacious therapies among symptomatic older adults, an increasing emphasis has been placed on preventive measures that can curb or even prevent ADRD development among middle-aged adults. Lifestyle modification using aerobic exercise and dietary modification represents one of the primary treatment modalities used to mitigate ADRD risk, with an increasing number of trials demonstrating that exercise and dietary change, individually and together, improve neurocognitive performance among middle-aged and older adults. Despite several optimistic findings, examination of treatment changes across lifestyle interventions reveals a variable pattern of improvements, with large individual differences across trials. The present review attempts to synthesize available literature linking lifestyle modification to neurocognitive changes, outline putative mechanisms of treatment improvement, and discuss discrepant trial findings. In addition, previous mechanistic assumptions linking lifestyle to neurocognition are discussed, with a focus on potential solutions to improve our understanding of individual neurocognitive differences in response to lifestyle modification. Specific recommendations include integration of contemporary causal inference approaches for analyzing parallel mechanistic pathways and treatment-exposure interactions. Methodological recommendations include trial multiphase optimization strategy (MOST) design approaches that leverage individual differences for improved treatment outcomes.

A Proposed Hypothesis on Dementia: Inflammation, Small Vessel Disease, and Hypoperfusion Is the Sequence That Links All Harmful Lifestyles to Cognitive Impairment

“…In contrast, there is growing consensus in the literature that dementia is not an inevitable companion to old age ( Qiu and Fratiglioni, 2018 ). Rather, cognitive decline appears more likely when certain lifestyles have been present ( Laurin et al, 2001 ; Serrano-Pozo and Growdon, 2019 ; Smith, 2019 ). This realization has shifted the scientific and social discourse in dementia from the search for a therapy to promoting prevention of the condition.…”

Cognitive Training as a Potential Activator of Hippocampal Neurogenesis in the Rat Model of Sporadic Alzheimer’s Disease

“…Alzheimer’s disease (AD) is a detrimental multifactorial disorder developing asymptomatically for many years prior to its manifestation [ 1 ]. There is no effective cure for AD at present; however, several individually modifiable interventions prior to manifestation of the disease symptoms are believed to improve cognitive function and to decrease the risk of AD [ 2 , 3 , 4 ]. Indeed, several studies have revealed positive associations of physical activity, cognitive training, or both with cognition in elderly people and patients with mild cognitive impairment [ 5 , 6 , 7 ].…”

Effects of Lifestyle Factors on Cognitive Resilience: Commentary on “What This Sunny, Religious Town in California Teaches Us About Living Longer”

“…Reducing the prevalence of each risk factor by 10% or 20% per decade could substantially decrease the worldwide prevalence of AD in 2050 by 8-15%, which translates to between 8.8 million and 16.2 million cases avoided [12,13]. Emerging evidence shows the beneficial effects of lifestyle interventions, such as those practiced by Adventists, on cognitive outcomes [13,16]. The Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) was the first large-scale long-term randomized controlled trial to assess the effects of a 2-year multidomain lifestyle intervention to prevent cognitive decline in at-risk elderly people (60-77 years) from the general population [17].…”

“…Exercise-induced structural and functional changes in the brain including increased total brain and hippocampal volume, improved cerebral blood flow, and increased gray and white matter integrity were observed, along with improvements in cardiorespiratory fitness [19,20]. While cognitive benefits of physical activity vary considerably across individuals, it has become increasingly clear that such activity reduces AD risk [16]. A Western diet high in red/processed meat, fatty foods, refined grains, and sugar has been associated with cognitive decline [21], whereas Mediterranean, Dietary Approaches to Stop Hypertension (DASH), and Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diets are associated with lower risk of AD and rate of cognitive decline [22].…”