Sport and health: physical activity prevents dementia in women

Middle-aged women with good physical fitness have almost a 90% lower chance of developing senile dementia decades later compared to less fit women. Physical activity, therefore, not only benefits cardiovascular health but can also protect against the cognitive decline typical of old age. Furthermore, if women who engage in a lot of aerobic exercise do develop dementia, the symptoms of this condition appear on average 11 years later than in others.

This is reported by a study led by Helena Hörder from the University of Göteborg, Sweden, and published in Neurology, the medical journal of the American Academy of Neurology.

Exercise helps prevent dementia through several mechanisms 

Numerous studies have shown that physical exercise is useful in preventing cognitive disorders and dementia in old age. It is presumed that the potential mechanisms underlying the protective effects of physical activity on cognitive function are multiple: Exercise is associated with a reduced risk of cardiovascular diseases, which in turn are factors predisposing to dementia.

• Physical exercise improves blood circulation and perfusion.
• Physical activity is associated with increased substances necessary for the growth and survival of neurons.
• Physical activity reduces substances responsible for oxidative stress.
• Physical activity is correlated with better nutrition, which positively improves cognitive performance.
• Physical activity facilitates social interaction and good mood.

At the brain level, aerobic exercise appears to make the brain more efficient, plastic, and adaptive, which leads to improved memory and executive function. Some animal model research has demonstrated that aerobic training increases the number of capillaries, the number of connections between brain cells, and the development of new neurons. In short, the mechanisms stimulated by regular physical activity include all those changes related to neuronal cell proliferation, particularly newly formed neurons that "connect" with others. 

A recent German study, for example, explored how physical exercise can influence brain metabolism by preventing excessive increases in choline, a substance very important for nervous system function. The results showed that physical exercise leads to stable choline concentrations in the brain in the "training" group, whereas choline levels were altered in the "control" group. According to the researchers, elevated choline levels can cause nerve cell loss, damage commonly occurring in Alzheimer’s disease. Alzheimer’s is the most common form of senile dementia and is caused by altered brain functions with very serious consequences for the patient, who finds difficulty even in performing normal daily activities. The disease affects brain areas involved in thought processing, memory, and language, causing amnesia, confusion states, personality changes, loss of control over bodily functions, mood swings, and spatial-temporal disorientation. 

Women who exercise have a lower risk of developing senile dementia  

The new study investigated the role that physical fitness plays in protecting middle-aged women from cognitive decline, revealing that females who had performed more aerobic physical activity showed up to an 88% lower risk of developing senile dementia compared to those moderately fit. Furthermore, highly fit participants who had shown cognitive deficits over the years exhibited first symptoms much later in life compared to others—about 11 years later; at age 90 instead of 79. "These results are exciting because it is possible that improving cardiovascular function in middle age can delay or even prevent the development of dementia," said Professor Hörder. "This suggests that negative cardiovascular processes that may manifest around age 50 could increase the risk of dementia later in life," she continued.

Some details of the research 

To conduct the research, 191 women with an average age of 50 were involved and classified according to their peak cardiovascular capacity. The women underwent a physical exertion test using a bicycle. The average workload was measured at 103 watts. A total of 40 women met the criteria for a high fitness level, equivalent to 120 watts or more; 92 women fell into the medium fitness category, while 59 women were classified in the low fitness level, represented by a peak workload of 80 watts or less. Participants in the latter group stopped the exercise test due to high blood pressure, chest pain, or other cardiovascular problems. The study continued over the following 44 years, during which the women were tested for dementia six times. After this period, a total of 44 women had developed senile dementia; 32% of these were those who had shown low fitness levels at the beginning of the study, compared to 25% of moderately fit women. Remarkably, only 5% of the women with senile dementia belonged to the highest physical activity level group.

Further studies will be needed to understand the beneficial role of exercise over the years. 

The reported study has some limitations; the main one is that it examined only women from Sweden, so the results are applicable to a limited number of people. Moreover, fitness levels of participants were measured only once, so any changes in performance over time were not recorded. According to the researchers who conducted the study, although the results show an association between fitness, cardiovascular health, and dementia, further studies will be necessary to demonstrate a concrete cause-and-effect relationship and to better determine whether increased physical exercise can have a positive effect on dementia risk and at which life stage it is most effective.

Source: Helena Hörder, Lena Johansson, XinXin Guo, Gunnar Grimby, Silke Kern, Ingmar Skoog. October 16, 2018; 91 (16). Midlife cardiovascular fitness and dementia: A 44-year longitudinal population study in women.