Establishing Reference Cardiorespiratory Fitness Parameters in Alzheimer’s Disease

Abstract

Evidence is growing for aerobic exercise training as a viable means to attenuate cognitive losses associated with Alzheimer’s disease. The mechanism of action for aerobic exercise’s cognitive benefits is likely enhanced cardiorespiratory fitness and its response to incremental aerobic exercise have been incompletely evaluated in Alzheimer’s disease. The aim of this analysis was to establish cardiorespiratory fitness reference values in older adults with mild to moderate Alzheimer’s disease using a cardiopulmonary graded exercise testing. Ninety-seven community-dwelling older adults with mild to moderate Alzheimer’s disease underwent a symptom limited cardiopulmonary graded exercise test on a cycle ergometer. Differences between sexes and between Alzheimer’s disease participants with and without diagnosis of cardiovascular diseases were assessed by independent T-tests. Peak oxygen consumption was 10–20% lower than those achieved by similar clinical populations on treadmill tests. As expected, males produced significantly higher peak oxygen consumption compared to females (p =0 .02). However, the presence of concurrent cardiovascular disease did not result in statistically significant lower peak oxygen consumption compared to those without cardiovascular disease. These data provide a frame of reference for metabolic, cardiovascular, and ventilatory function during cardiopulmonary graded exercise testing performed on cycle ergometer in older adults with mild to moderate Alzheimer’s disease.

Exercise Dose and Aerobic Fitness Response in Alzheimerʼs Dementia: Findings from the FIT-AD Trial

“…Given the importance of CRF as a mediating factor on brain volume [46], cerebral blood flow [35], AD risk factors [47] and cognition [48], establishing a dose-response relationship is clinically important for determining the minimally, maximally, and optimally effective doses of AEx on not only CRF and cognition, but also activity of daily living performance as it is an extremely important outcome for people with AD to be as independent as possible and to increase their quality of life. Additionally, the results of this study along with previous findings regarding inter-individual variability in CRF response to AEx [41] and the impaired cardiopulmonary function seen in this population [25], suggests a need for a precision exercise approach to rehabilitation. First, alternative types of AEx should be explored in persons with AD, such as high intensity interval training, known to be superior to moderate intensity AEx for improving CRF in older, cognitively intact adults [49].…”

“…Another explanation for the attenuated CRF response is that individuals with mild-moderate AD may have a limited, or more variable, physiologic response to AEx than cognitively normal individuals. Previous studies have demonstrated that baseline CRF indicators including VO 2Peak , minute ventilation, and oxygen pulse are lower in persons with AD compared to age- and sex-matched normative data 25 . Additionally, previous analyses have also showed the considerable inter-individual variability in CRF response to AEx in persons with AD 41 that could explain the findings in this study.…”

“…CPET. Participants completed a CPET on a recumbent cycle ergometer (Precor 842i, Woodenville, WA) as previously published [25]. Briefly, cadence was set at 40-60 revolutions per minute [rpm]) and the intensity of cycling was then increased every three minutes (one stage) by increasing the cycle resistance (and therefore watts [W]) to achieve an increase in energy expenditure of one metabolic equivalent (MET).…”

Cognitive Effects of Aerobic Exercise in Alzheimer’s Disease: A Pilot Randomized Controlled Trial

“…Our findings support the clinical relevance of promoting aerobic exercise in individuals with AD dementia. Analyses of our baseline data showed that our participants had substantially lower aerobic fitness in comparison to age- and gender-matched peers [ 47 ] and have an average of 3.5 comorbidities, and both issues are amenable to aerobic exercise. Although we did not measure quality of life, participants and family caregivers had consistently and overwhelmingly expressed the positive impact of exercise on their lives.…”

Aerobic Exercise, Training Dose, and Cardiorespiratory Fitness: Effects and Relationships with Resting Plasma Neurotrophic Factors in Alzheimer’s Dementia

“…CRF Cardiopulmonary exercise test. Participants completed a CPET on a recumbent cycle ergometer (Precor 842i, Woodenville, WA, USA) at the University of Minnesota's Laboratory of Clinical Physiology, as previously published [47]. Expired gases were measured continuously by a respiratory mass spectrometer (MGA 1100, Beck's Physiological Systems, St. Louis, MO, USA), with breath-by-breath analysis averaged over 30 s intervals.…”