“Good news,” a friend in the gym said, waving her cell phone in my direction. She showed me a news release about a study on the positive effects of exercise in preventing dementia among women. The article published in Neurology (link is external) showed the somewhat startling relationship between being very fit and reducing by almost 90%, the chance of becoming demented.
An air of self-congratulation rippled through the treadmill walkers as the news passed from machine to machine, and there seemed to be a perceptible increase in the intensity of the exercise we were all doing.
Unfortunately, a closer reading of the study revealed that even those who went to the gym pretty regularly were not guaranteed a dementia-free future. Unless we were extremely physically fit we were still vulnerable to cognitive problems as we age.
The study was initiated in l968 when researchers tested the cardiovascular capacity of Swedish women ranging in age from 38 to 60. The women exercised on an exercise bike that monitored their cardiovascular stamina, and they were told to exercise until exhaustion. One hundred and ninety-one women participated and, based on how well they did on this test, were divided into high, medium and low fitness levels. Some in the low fitness group were unable to complete the exercise because of cardiovascular problems. Forty placed in the high fitness group, ninety-two in the medium-fitness group and fifty-nine in the lowest group. Those in the high fitness group were not competitive athletes, but their physical stamina and energy utilization measured during the initial testing period indicated their ability to endure strenuous exercise.
Women were tested six times over the subsequent 44 years of the study to determine if and when dementia appeared. The bad and good news is that 32% of the least fit developed dementia, as did 25% of the medium-fit. However, only 5% of the fittest group were affected.
Dementia is not the same as memory loss, although it can be associated with it. Dementia is not a specific disease, but instead describes a cluster of symptoms that affect intellectual functioning, emotional control, the ability to solve problems, maintain language skills, and carry out the functions of daily life. One example of the difference between memory loss and dementia is a person who cannot remember the name of a fork but can still use it to eat. This person has memory loss, but may not be demented. A person who doesn’t know the name of a fork nor its function would be considered to be suffering from dementia.
In the Swedish study, the most common cause of dementia was Alzheimer’s disease (eighty women), although twelve women developed vascular dementia. The latter is usually associated with strokes, some so small they are not even detected. The other causes of dementia were not described.
Before giving up one’s day job to spend more time in the gym to increase physical fitness, it is important to consider that the authors of the study were not sure how being especially fit protected the women from dementia. Nor did were they able to explain why the least fit women were so vulnerable. Moreover, the study did not record whether the women continued to be fit or not during the several decades that followed the initial assessment, and their physical fitness was never measured again.
This sort of study is frustrating on many levels. It is not a cause and effect study, i.e., exercise causes something that protects against dementia. Rather it shows the linkage of two conditions: peak fitness in middle age and significantly decreased incidence of dementia almost 50 years later.
So is it the exercise itself that may alter the brain to prevent cognitive decline? If so, how? Do women with outstanding stamina have different lifestyles? Do they also do crossword puzzles more often or speak several languages, activities that are supposed to improve brain function? The study was done in Sweden, but perhaps the high fitness subjects followed a Mediterranean diet eating mostly grains, fish, olive oil and vegetables. Such a diet has loosely been linked to lower rates of Alzheimer’s disease.
Was there a connection between the levels of their female hormones and their exercise activity? Maybe those who exercised so well didn’t suffer from menopausal hot flashes. Or maybe they did. Who knows?
Does their fitness at fifty result from a childhood and early adulthood spent in strenuous physical activity? If so, might the positive change in their brain preventing dementia be a result of decades of peak exercise performance and perhaps, along with that, food intake designed to enhance this performance? Should we encourage our children and grandchildren to take on sustained high levels of physical activity, so by the time they are fifty, their brains may be protecting them against dementia?
This study probably took fifty or more years to carry out because of the time spent gathering and testing subjects before it began, and the time spent analyzing the data after it was over. Such studies are difficult to do, and certainly repeat, which is impossible to do in the lifetime of the original investigators. The results are tantalizing and sufficiently compelling to make some, perhaps with a family history of dementia, commit to more exercise, more frequently, and with greater intensity. And if it works to prevent Alzheimer’s disease and other causes of dementia, then regardless of why or how it will be worth doing.
“Midlife cardiovascular fitness and dementia,” Hörder, H., Johansson, L., Gu, X., et al, Neurology Mar 2018, 10:1212