The impact of estimated cardiorespiratory fitness on Alzheimer's disease biomarkers and their relationships with cognitive decline.

INTRODUCTION

The accumulation of core Alzheimer's disease (AD) pathology contributes to cognitive decline. Cardiorespiratory fitness (CRF) influences AD pathological progression resulting in improvement or maintenance of cognitive function with age. CRF-related differences in accumulation rates or risk of reaching clinically relevant AD biomarker levels, and potentially interactive effects of core AD pathology and CRF on cognitive decline, remain largely unknown.

METHODS

Participants ( = 533; Mean = 65, 70% female) from the Wisconsin Alzheimer's Disease Research Center and the Wisconsin Registry for Alzheimer's Prevention underwent serial blood draws, and cognitive and imaging assessments (Mean = 6.0 years). Positron emission tomography (PET) imaging of amyloid beta (Aβ) and tau (T) and plasma phosphorylated tau-217 (p-tau217) were used to determine biomarker status (±). Sex-specific estimated CRF (eCRF) tertiles were created using a validated equation. Kaplan-Meier survival curves and Cox proportional hazards examined the risk of becoming biomarker-positive. Linear mixed-effects models, stratified by biomarker status, estimated associations between baseline eCRF and core AD biomarker accumulation, and whether eCRF modified relationships between biomarker accumulation and cognitive decline.

RESULTS

There were no significant relationships between eCRF and biomarker trajectories. However, those in high eCRF group who were Aβ- at baseline had a significantly lower risk of becoming biomarker-positive (Aβ-PET: HR, 95% confidence interval [CI] = 0.42, 0.20-0.88; p-tau-217: 0.45, 0.21-0.97) compared to the low eCRF group. The detrimental relationship between Aβ accumulation and cognitive decline was significantly attenuated for Aβ+/T+ with high eCRF.

DISCUSSION

Although eCRF did not influence core AD biomarker accumulation trajectories, high eCRF seems protective against becoming biomarker-positive and attenuates the known deleterious relationship between biomarker accumulation and cognitive decline in Aβ+/T+.

HIGHLIGHTS

High estimated cardiorespiratory fitness (eCRF) is associated with a lesser likelihood of becoming AD biomarker positive.High eCRF did not alter biomarker accumulation in those positive for Alzheimer's disease (AD) pathology.High eCRF attenuated the relationship between AD biomarkers and cognitive decline.Innovative methods: Stratifying analyses by amyloid beta and tau status.