Lifestyle and exercise

Will keeping fit fight Alzheimer’s?

“Exercise 'slows down Alzheimer's'” is the headline on the BBC News website today. A study in people aged over 60, about half of whom were in the early stages of Alzheimer’s disease, compared people with Alzheimer's who were less fit with those who were fit, and found that the less fit group had “four times more signs of brain shrinkage”.

The study on which this story is based looked at fitness and brain volume at one point in time. Because of this, it is not possible to know whether people who kept fit slowed the brain shrinkage associated with their Alzheimer’s, or whether Alzheimer’s causes both brain shrinkage and a loss of fitness. A study looking at the sequence of events will be needed to establish which of these scenarios is more likely.

Maintaining a healthy lifestyle has known benefits for people of all ages. Although this study has not proven that keeping fit can reduce your risk of Alzheimer’s or slow its progress, this is no reason to stop aiming for fitness.

Where did the story come from?

Dr Jeffrey Burns and colleagues from the University of Kansas and its School of Medicine carried out this research. The study was funded by the National Institutes of Aging, National Institute on Neurological Disorders and Stroke, and the University of Kansas Endowment Association and the Fraternal Order of Eagles. It was published in the peer-reviewed medical journal: Neurology .

What kind of scientific study was this?

This was a cross-sectional study that aimed to look at the relationship between fitness and brain size in people with and without early-stage Alzheimer’s disease (AD).

The researchers enrolled 121 adults aged over 60 years old (mean age 73.5) who either had early-stage AD (57 people) or no signs of dementia (64 people). Potential participants were assessed in an interview, and additional information was obtained from someone who knew them well (e.g. a family member or carer). To be diagnosed with AD, the person had to have a gradual loss of memory and impairment in at least one other aspect of cognition or function that worsened over time. People were also rated on the Clinical Dementia Rating (CRD) scale: a score of 0 indicated no sign of dementia, and a score of 0.5 or 1 indicated early-stage AD. People with brain disorders other than dementia were excluded, as were people with diabetes, a history of heart disease, schizophrenia, significant symptoms of depression, significant visual or hearing impairment, physical illness or bone problems that would hinder participation. Participants were assessed using tests of cognition, memory, habitual physical activity and physical frailty.

The participants took part in treadmill testing to calculate their peak oxygen consumption (VO2peak) – a standard measure of cardiorespiratory fitness. The 17 participants who could not complete this test successfully were also excluded from the analyses. The researchers used MRI scanners to look at the participants’ brains and calculate their brain volume. The researchers then looked at the relationship between brain volume and fitness in the AD and non-AD groups. Brain volume was adjusted for gender. The analyses were also adjusted for other factors that might affect brain volume and fitness (confounding factors), such as age, dementia severity, habitual physical activity and physical frailty.

What were the results of the study?

The researchers found that people with early AD had less cardiorespiratory fitness (lower VO2peak) than those who did not have signs of dementia. People with early AD had signs of shrinking of the brain and those who had greater shrinking of the brain also had greater impairment of their cognitive function.

People with early AD who had higher levels of cardiorespiratory fitness had less shrinking of the brain than those who had lower levels of fitness. This association remained even after the researchers adjusted for potential confounding factors. There was no association between brain volume and fitness in people without dementia.

What interpretations did the researchers draw from these results?

The researchers concluded that in people with early AD, increased cardiorespiratory fitness was associated with less brain atrophy (shrinkage). They suggest that either fitness may directly reduce or delay brain atrophy, or some common aspect of AD may affect both fitness and brain atrophy.

What does the NHS Knowledge Service make of this study?

There are a number of points to consider when interpreting this study:

  • The main limitation to the interpretation of this study is its cross-sectional design. Because it looked at both fitness and brain volume at the same point in time, it cannot prove that exercise reduced or delayed brain atrophy. It is also possible that AD either directly affects people’s fitness by affecting their muscles, or indirectly reduces their fitness by making them less likely to exercise. Prospective studies will be needed to assess which of these scenarios is correct.
  • This study is relatively small and may not be representative of the AD population as a whole.
  • Alzheimer’s disease can only be definitively diagnosed post-mortem; therefore it is possible that some of the AD group had other forms of dementia or other conditions. It is also possible that some of the non-AD group had very early changes in their brains, which were not currently affecting their cognition but would eventually lead to dementia.

Maintaining a healthy lifestyle has known benefits for people of all ages. Although this study has not proven that keeping fit can reduce your risk of Alzheimer’s or slow its progress, this is no reason to stop aiming for fitness.

NHS Attribution