“Walking, gardening or doing housework for 30 minutes most days can cut the risk of dementia by one third,” reported_ The Daily Telegraph_ . A study found that pensioners who were most active in their daily lives were least likely to develop vascular dementia, the newspaper said.
The report is based on a study in elderly Italians and has highlighted an association between levels of activity and the risk of a particular type of dementia (vascular dementia), but not the overall risk of dementia, or of Alzheimer’s disease.
Where did the story come from?
Dr Giovanni Ravagalia and colleagues from University Hospital S. Orsola-Malpighi in Bologna, Italy carried out this research. The study was supported by grants from the Italian Ministry of University and Scientific Research. It was published in the peer-reviewed medical journal: Neurology .
What kind of scientific study was this?
The study was a prospective cohort study to explore the association between physical activity and the risk of dementia (vascular dementia, Alzheimer’s disease, or either of these). Information about cognitive function and physical activity was collected from elderly people in a region of Italy as part of another study (the Conselice Study of Brain Ageing [CSBA]) in 1999/2000.
In order to monitor physical activity, people were asked how far they walked, how many flights of stairs they climbed, and about other recreational and sport activity. The 749 people who didn’t have dementia, mild cognitive impairment or a physical problem that prevented them exercising at the start of the study were traced again in 2003/2004 to determine whether they had developed dementia over the previous four years. These people were then assessed for dementia using well-known questionnaires.
Where the participant was no longer alive, or was not able to respond because of their physical or mental condition, their diagnoses were established through the help of a relative. The researchers then assessed whether the participant’s levels of physical activity at the start of the study were linked to any diagnosis of dementia in 2003/2004.
What were the results of the study?
The researchers found that people who walked the most were about three times less likely to develop vascular dementia compared with those who walked the least. A similar reduction in risk was seen in people who spent the most about of energy doing moderate activity (house work, yard work, gardening etc.) compared with those who spent the least. Similarly, those who did the most physical activity per week were three times less likely to develop vascular dementia than those who did the least.
There was no association between risk of Alzheimer’s disease and levels of physical activity. There was no association between the overall risk of dementia of any type and levels of physical activity. These results took into account other factors, such as comorbidities, gender, age, education, socioeconomic status, genetics, and cardiovascular health; all of which could be contributing to the risk of dementia.
What interpretations did the researchers draw from these results?
The researchers concluded that physical activity is associated with a lower risk of vascular dementia but not of Alzheimer’s disease. They put forward some theories as to why this might be the case, but call for further research to understand the “biologic mechanisms operating between physical activity and cognition”.
What does the NHS Knowledge Service make of this study?
This prospective study has shown an association between levels of physical activity and the development of vascular dementia. Considering the benefits of activity on cardiovascular health, it is not unexpected that there may be such a relationship between vascular dementia and exercise. However, the study has important limitations – some of which the researchers raise – that should be kept in mind when interpreting the findings:
- Some people with early dementia may have been included in the study because the initial screening and diagnosis was not good enough. This might mean that it was vascular dementia causing reduced physical activity, rather than the other way around. According to the researchers, the study “cannot establish causal relationships and a four-year follow up is too short an interval to completely rule out the possibility that lower physical activity was not a cause but an early symptom of dementia”.
- Though the researchers adjusted for a number of factors that could be linked to dementia, there may be others that they haven’t considered. This is a possible weakness of all cohort studies and is the reason why questions such as “can exercise reduce the risk of dementia?” are better answered using randomised controlled studies.
- Levels of activity are unlikely to have stayed constant throughout the four-year follow up for every person, particularly as age was increasing. Physical activity was measured only at the start of this study.
- The researchers also say that their results may not be generalisable as their sample had “a poor educational background and rural upbringing” and that their reliance on CT scans (rather than MRI scans which are thought to be better) is a weakness in their design.
Further, better-designed research is needed before it is clear whether exercise reduces the risk of vascular dementia. There are other more well established reasons why physical activity should be encouraged throughout a person’s life.
Sir Muir Gray adds...
I believe that walking is the single best preventive action; free and free from risk so I am biased in favour of results like this. The study produces results that need to be reviewed systematically, along with other studies of walking. However, I won’t be waiting for the results of this review; I will be walking an extra thirty minutes every day, and maybe when I reach seventy I will up the vital steps to 4000 a day.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
The Daily Telegraph, 20 December 2007
Links to the science
Neurology 2007; Dec 19 [Epub ahead of print]