Proof That Exercise Defeats Dementia – Or Is It?

health care worker helping a senior
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You’ll often read an article saying that there is “proof” or that researchers have “proven” a connection between two things, but researchers actually use the word “proof” very hesitantly. Here’s a study on the topic of exercise and dementia that might make you think carefully about how this term is used.

The study appeared in the journal Neurology entitled Midlife cardiovascular fitness and dementia: A 44-year longitudinal population study in women (the study is also nicely summarized here by CNN). The following research was conducted and some convincing results were found:

  1. 191 Swedish women (38 to 66 years old) were given tests of their cardiovascular fitness
  2. During the tests (which consisted of exercise on a stationary bike) their blood pressure was monitored and they were connected to an electrocardiograph.
  3. Based on their results, “…the women were separated into three groups: 59 were placed into the “low fitness” group, 92 were designated as “medium fitness,” and 40 were labeled as “high fitness.”
  4. The tests were given in 1968 and the women were followed for 44 years to see who was diagnosed with dementia.

Results: Overall, 23% of the women in the study developed dementia.  However, 45% of those in the “low fitness” group developed dementia.

Proof, then, that exercise can prevent dementia?

Actually, this study, as impressive as it is, CANNOT lead us to a confident conclusion about the role of exercise in warding off dementia. The results are correlational and, as we know, correlation does not demonstrate causation.

The problem here is that people who exercise may also eat a more balanced diet. So is it diet or exercise (or both) that leads to the decrease in dementia? Could people who exercise more also socialize more….?

So while the study can be said to “provide some evidence” in favor of a causal link between exercise and dementia, it cannot offer “proof”. We really don’t know – for sure – what those high fitness women did during their lives to result in their lower levels of dementia.

The one factor that gives us some confidence that exercise can decrease your chances of developing dementia is that there are quite a number of studies – conducted in very different ways – that also point to this connection.

Discussion Questions and Activities

If you’d like to explore this idea with students, have them work in groups of 2-3 to see if they can generate some alternative hypotheses to the results. Here are questions to ask:

  1. Why is this issue of exercise and dementia a difficult one to study?
  2. How would YOU set up a different study to test the link between exercise and dementia?

Students might want to present their ideas to class. Other students can give their opinion on whether or not the ideas presented by each group would lead to strong conclusions or weak ones on this connection between exercise and dementia. If students are not clear on the group’s ideas, ask questions like:

  • Can you give an example of what you’re talking about?
  • Could you be more specific?

Remember that no one study can prove a link, but taken together they can give us confidence in a link.