We've long known that exercise is great preventive medicine, but we generally think of it in terms of curbing the risk of cardiovascular disease, diabetes or even cancer. Now, in one of the first studies of its kind, researchers have found that physical fitness also lowers the risk of dementia-related death.
While cardiovascular and cancer deaths are on the decline, deaths from dementia and Alzheimer's are on the rise. According to the study's authors, deaths related to dementia increased by 46 percent between 2002 and 2006 alone. And some of that may have to do with fitness: lead researcher Rui Liu -- a fellow at the National Institute of Environmental Health Sciences at the NIH -- and her team found that being out of shape more than doubled the risk of dying from a dementia-related cause.
The study, published in Medicine & Science in Sports & Exercise, the official journal of the American College of Sports Medicine, found a link between the two -- not a cause and effect. But what makes this study unique is the use of clinical measures of fitness. “Cardiorespiratory fitness is preferable to self-reported physical activity because it is an objective, reproducible measure that is more closely correlated with a person’s usual level of physical activity and many health outcomes,” said Liu in a statement. In other words? People are rarely truthful about their fitness in surveys -- chances are, we're all under- or over-estimating how fit we are.
Liu used baseline data collected in 1986 by researchers at the Cooper Clinic in Dallas. That data included blood tests, medical history questionnaires, health habits surveys and other clinical measures of physical fitness of more than 60,000 adults, including 14,811 women and 45,078 men between the ages of 20 and 88 years. Everyone was categorized into one of three groups: low fit, middle fit or high fit.
By 2003, 17 years later, 4,047 of the participants had died, according to the National Death Index, with 164 of those deaths attributed to either vascular dementia or Alzheimer's. When Liu matched each study participant's fitness level to a death record, she found that 123 of the 164 were in the 'low fit' category, while 23 were medium fit and 18 were high fit. That means 'low fit' individuals of any age more than doubled the risk of dying of dementia than those in the 'medium fit' and 'high fit' categories.
In many ways, this finding supports what we already know: cardiovascular health improves oxygen and blood flow to all organs, including the brain. In fact, a recent study from the Journal of Neurology found that running and walking helped minimize arterial plaque build-up and, in turn, helped study participants score better on tests of memory and mental acuity.