Published on: March 18, 2012
by Helping You Care
A recently published study has found that when approximately 60,000 adults were tested and ranked — as high, middle or low — for their level of cardiorespiratory fitness, those with medium or high levels of fitness had less than half the risk of dying from dementia over a 17 year follow-up period than the participants with a low level of fitness.
The study was conducted by Rui Liu, PhD, now a postdoctoral fellow at the U.S. National Institute of Environmental Health Sciences, part of the National Institutes of Health, and her colleagues. The study was published in the February 2012 issue of the journal Medicine & Science in Sports & Exercise, the official journal of the American College of Sports Medicine.
This study is one of the first to examine the relationship between objectively measured cardiorespiratory fitness levels and dementia-related deaths in a large sample, including more than 45,000 men and nearly 15,000 women.
Several other, previous studies have also linked exercise and fitness to lower risks of mental decline and dementia. However this is one of the first studies to measure fitness through objective cardiorespiratory stress tests rather than merely self-reported exercise levels, which may be open to over- or under-estimation and error.
“A major strength of our study is the use of standardized and objective physical activity measurement,” Dr. Liu said in a news release about the study issued by the American College of Sports Medicine (ACSM). “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,” she said.
Due to public health efforts in the U.S., deaths from heart disease, breast cancer and stroke have gradually declined over the past few years, according to the ACSM’s news release. “Deaths related to dementia and Alzheimer’s disease, however, have increased dramatically over the last 15 years, skyrocketing 46 percent between 2002 and 2006,” the release states.
While the authors point out that their study does not prove that exercise causes a decline in dementia deaths, it does show a strong relationship between fitness and a significantly reduced risk of dying from dementia.
The Study; Methodology
At the beginning of the study, researchers conducted examinations and maximal cardiorespiratory exercise tests on 14,811 women and 45,078 men, ages 20-88 years, at the Cooper Clinic in Dallas. The examinations included a questionnaire on personal and family medical history, demographic information and health habits, as well as blood chemistry tests, and other clinical measurements of health and fitness.
Cardiorespiratory Fitness was measured with a maximal treadmill exercise test, with results expressed in maximal METs.
The participants were grouped into one of three fitness categories – low fitness, middle fitness or high fitness – based on their performance on the fitness test.
After an average follow-up period of 17 years, 4,047 of the participants had died. According to the National Death Index, 164 of those deaths were attributed to dementia (72 vascular dementia and 92 Alzheimer’s disease).
The researchers used statistical analysis to examine the association between fitness at the beginning of the study and dementia mortality, after controlling and adjusting for age, sex, examination year, body mass index, smoking, alcohol use, abnormal ECGs, and health status.
Of the 164 study participants who died from dementia, 123 were in the low-fitness category, 23 were in the medium-fitness category, and 18 were in the high-fitness category.
The risk of dying with dementia of the participants in the middle- and high-fitness groups was less than half that of those in the lowest fitness group, the researchers concluded.
“Each 1-MET increase in fitness was associated with a 14% lower adjusted risk of dementia mortality (95% confidence interval (CI) = 6%–22%),” the authors reported.
“Greater fitness was associated with lower risk of mortality from dementia in a large cohort of men and women,” the authors concluded.
“These findings support physical activity promotion campaigns by organizations such as the Alzheimer’s Association and should encourage individuals to be physically active,” study author Riu Liu said in the American College of Sports Medicine’s news release accompanying publication of the study.
“Following the current physical-activity recommendations from the American College of Sports Medicine will keep most individuals out of the low-fit category and may reduce their risk of dying with dementia,” Dr. Liu added.
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