A Swedish study of 191 women examined their fitness levels in mid life, before tracking them for 44 years. Participants were asked to carry out exercise tests on a bike to measure their cardiovascular activity.
The research found that those with the highest fitness levels when first assessed had just a five per cent chance of developing dementia in subsequent decades. This compared with rates of 25 per cent among those who performed moderately. Rates were even worse among those with low fitness and among those so unfit they could not complete the tests, the study by the University of Gothenburg in Sweden found. Overall, those who dropped out of the tests had dementia rates of 45 per cent in later life.
And when highly fit women developed the disease, on average it came 11 years later than among those with moderate levels of fitness - at age 90 instead of age 79.
For the study, 191 women with an average age of 50 took a bicycle exercise test until they were exhausted to measure their peak cardiovascular capacity. The average peak workload was measured at 103 watts. A total of 40 women met the criteria for a high fitness level, or 120 watts or higher, while 92 women were in the medium fitness category. A total of 59 women were in the low fitness category, defined as a peak workload of 80 watts or less, or having their exercise tests stopped because of high blood pressure, chest pain or other cardiovascular problems.
Over the next 44 years, the women were tested for dementia six times. During that time, 44 of the women developed dementia. Five per cent of the highly fit women developed dementia, compared to 25 per cent of moderately fit women and 32 per cent of the women with low fitness.
Dr Hörder added: "This indicates that negative cardiovascular processes may be happening in midlife that could increase the risk of dementia much later in life."
Dr David Reynolds, chief scientific officer at Alzheimer’s Research UK, said: “We know that exercise can improve heart health and it has also been linked with a reduced risk of dementia. By working with participants over many years, this study has highlighted how fitness in mid-life can help predict dementia risk years later.
"While studies like this can’t definitively show cause and effect, it adds to research suggesting that middle age is key time for people to take steps to promote their brain health.”
Dr Reynolds said boosting exercise did not have to meet major exertion.
“Physical exercise doesn’t necessarily mean going to the gym or running a marathon, but something that can easily be fitted in as part of the normal routine, like a jog or a brisk walk with friends. Alongside regular exercise, the current best evidence to maintain good brain health as we age is to eat a balanced diet, maintain a healthy weight, not smoke, and keep blood pressure and cholesterol in check,” he said.