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Dementia study debunks exercise theory


Look at any of the multitude of articles of the past few years on how to avoid dementia and you’ll almost certainly read that exercise delays onset. Not so, according to the most recent research, published this week in the BMJ.

The 28-year study followed over 10,000 middle-aged British civil servants, noting at seven-year intervals whether participants were doing the “recommended” amount of exercise, defined as moderate or vigorous physical activity for 2.5 or more hours per week.

Surprisingly, the researchers found no correlation between how much exercise a patient did and whether they experienced cognitive decline over the study period, identified through a battery of cognitive tests, along with dementia diagnoses from hospital and mental health services.

The finding runs counter to several recent meta-analyses of observational studies which concluded that physical activity is neuroprotective in cognitive decline and dementia risk.

What the researchers did find was that in participants who eventually developed dementia, a decline in physical activity started around nine years before diagnosis.

This finding could be key to why previous observational studies have found a correlation between exercise and dementia risk, say the French researchers from the Centre for Research in Epidemiology and Population Health in Paris.

It’s now well known that brain changes start happening many years before dementia symptoms become apparent, and a decrease in physical activity is probably part of the cascade of changes in this preclinical phase of dementia, the researchers say.

The upshot is that findings of a lower risk of dementia with exercise may be attributable to reverse causation – in other words, decline in physical activity is due to the dementia, and not the other way around.

The researchers say that two problems with some of the earlier observational studies were that their duration was too short and their participants were too old. This made them more liable to be confounded by participants with preclinical dementia, who for that reason had lower levels of physical exercise.

They also point out a difference between observational and randomised trials, with the latter less likely to find a protective effect with exercise.

The recommendation of exercise for the prevention of dementia has already become enshrined in a number of international guidelines, including in Australia.

You can access the study here.

The one thing that helps in chronic disease

Exercise, exercise and more exercise should be recommended to people with non-communicable chronic diseases, say Finnish researchers.

And it doesn’t necessarily matter what kind of exercise, or even what kind of chronic disease the patient has, according to a new umbrella review of 85 meta-analyses.

Aerobic exercise, resistance training, or a combination of both all improved functional capacity in roughly equal measure across 22 common chronic diseases, in randomised trials comparing exercise therapy with no treatment or usual care.

Chronic diseases in the review included osteoarthritis, rheumatoid arthritis, coronary artery disease, heart failure, type 2 diabetes, various cancers and Alzheimer’s disease.

The review encompassed 146 physical and functional capacity indicators, such as the six-minute walking test, maximal lower body muscle strength, balance tests and self-assessed ability to carry out everyday functions. Around 85% of these indicators were improved with exercise, with 20% showing large improvement.

These improvements were similar in both objective performance measurements and patients’ own assessment of their function.

At the same time, reported adverse events were no greater in exercise versus control groups.

The study authors from the University of Jvaskyla say research into exercise in chronic conditions has generally been more focused on risk factors, prevention and risk of death, and has often overlooked the importance of physical functioning.

Better function improves coping with daily living and may lessen pain and even disease progression, the researchers say. On a societal level, there are also economic benefits in reducing care needs of people with chronic conditions and improving their ability to live at home.

The authors suggest exercise therapy should be recommended to all patients with non-communicable chronic diseases, although training programs should be progressive and include follow-ups to monitor adherence, effectiveness or any adverse effects.

You can read the study here.