Review: Cardiorespiratory Fitness and Temporal Lobe Volume In Alzheimer’s Disease

There is a paper titled ‘Cardiorespiratory fitness and preserved medial temporal lobe volume in Alzheimer’s Disease’ by Honea and colleagues and freely available here. The researchers in this paper are asking the question ‘Is there a relationship between cardiovascular fitness and cortical lobar volume in people with Alzheimer’s Disease?’. To answer this question they have utilised a cross-sectional design and have compared structural MRI determined brain volume with a measure of cardiovascular fitness.

The researchers recruited a group of people with early stage Alzheimer’s Disease over the age of 65 (n=61) and also a control group (n=56) from a memory clinic. The Clinical Dementia Rating scale was used as a cut-off for identification of caseness. The researchers also go into some detail about the imaging methodology specifying the SPM software version as well as the details of the image analysis protocols. They use a 3 Tesla MRI scanner and a large number of outcome measures. The researchers also use a number of exercise physiology measures including peak flow and the participants undergo exercise on a treadmill.  In the analysis they control for multiple comparisons and specify the statistical cut-off points.

There are a large number of findings but there were several I found interesting

1. There was no relationship between dementia severity and peak oxygen consumption. However given the large number of possible confounders this isn’t too surprising and it would have been more interesting to see the results in a prospective study.

2. There was a significant relationship between temporal lobe volume in the Alzheimer’s Disease group and peak oxygen consumption suggesting a possible benefit of aerobic exercise capacity and a protective marker.

3. The relationship described in 2. was absent in the control group.

The researchers have produced an interesting discussion. I thought that perhaps the oxygen consumption and other exercise related measures might be markers of short term exercise capacity and that the longer term exercise capacity might be more relevant. This however would require a long term prospective study over many decades. There have been a few studies that have used questionnaires to estimate exercise capacity in long term longitudinal designs but this study combines neuroimaging and exercise physiology to offer a unique perspective on the important question of the relation of exercise as a protective factor in dementia. However it would be interesting to see how the constraints of medical comorbidity impact on this relationship.

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