Could physical fitness in middle age influence the risk of dementia?
Dementia, an umbrella term for a range of neurodegenerative diseases characterized by progressive memory loss and other cognitive impairments, affects approximately 50 million people worldwide, according to the World Health Organization (WHO).
Many risk factors are related to lifestyle, which means that by changing certain habits and leading a more healthful life, a person's risk of dementia can be decreased.
A new study from the University of Gothenburg in Sweden has now found that women who are very physically fit in middle age have an almost 90 percent decreased risk of being diagnosed with dementia later in life, unlike their moderately fit peers, who are more exposed to this condition.
The results of this study — which was led by Helena Hörder — were published yesterday in the journal Neurology.
Fitness cuts risk by 88 percent
For the purpose of the study, the researchers worked with 191 women, aged 50, on average. The participants' cardiovascular fitness — or their ability to sustain physical effort over a prolonged period — was assessed through a bicycle exercise test.
Hörder and team asked the women to participate in the exercise until they felt physically exhausted; this allowed the researchers to establish what each participant's peak cardiovascular capacity was.
In specialty literature, this peak capacity is defined as "the maximum ability of the cardiovascular system to deliver oxygen to exercising skeletal muscle and of the exercising muscle to extract oxygen from the blood."
The researchers behind this new study measured average peak workload at 103 watts.
Following these assessments, 40 women qualified as highly physically fit (120 watts or higher peak workload), 92 women exhibited medium fitness, and 59 women had low fitness levels (80 watts or lower peak workload).
Some of the women in the latter category had to interrupt exercise participation due to hypertension, chest pain, or other cardiovascular symptoms.
The participants were then followed-up over a period of 44 years, during which time they were assessed for dementia six times. During that time, 44 of the participants developed the condition.
Of the women who has scored as highly fit, only 5 percent were diagnosed with dementia in that 44-year interval. In contrast, 25 percent of the moderately fit participants and 32 percent of the women with low physical fitness levels developed the disease.
In other words, the women who were highly fit in middle age had an 88 percent lower risk of dementia than their moderately fit counterparts.
Also, the highly fit women who ended up receiving a dementia diagnosis did so at a much later stage in their lives — 11 years later, on average, than moderately fit women.
'Exciting findings' may speak to prevention
Another notable finding is that among the women who had been forced to cease exercise participation due to cardiovascular problems, 45 percent went on to develop dementia.
"This indicates," says Hörder, "that negative cardiovascular processes may be happening in midlife that could increase the risk of dementia much later in life."
"These findings are exciting because it's possible that improving people's cardiovascular fitness in middle age could delay or even prevent them from developing dementia."
At the same time, however, Hörder warns that "this study does not show cause and effect between cardiovascular fitness and dementia, it only shows an association."
She continues, saying, "More research is needed to see if improved fitness could have a positive effect on the risk of dementia and also to look at when during a lifetime a high fitness level is most important."
The study also had a number of limitations, such as the limited population sample, the specificity of the cohort — all of the women were Swedish, meaning that the results may not hold true for other populations — and the fact that the women's levels of fitness were only assessed at one point in the beginning of the study.
This, Hörder explains, may mean that possible changes in fitness levels following that initial test were not accounted for.