- Also, Antioxidant–Rich Diet Improves Memory and Learning in Alzheimer's Mice -
Evidence from three long-term, large-scale studies supports the association of physical activity and certain dietary elements (tea, vitamin D) with possibly maintaining cognitive ability and reducing dementia risk in older adults, according to new research presented today at the Alzheimer's Association International Conference on Alzheimer's Disease 2010 (AAICAD 2010) in Honolulu, HI.
Plus, a new study in an animal model of Alzheimer's reported today at AAICAD 2010 suggests that an antioxidant-rich diet with walnuts may benefit brain function.
"Research has pointed us towards a number of factors that may impact our risk of Alzheimer's and cognitive decline, the strongest being reducing cardiovascular risk factors," said William Thies, PhD, Chief Medical and Scientific Officer at the Alzheimer's Association. "The Alzheimer's Association and others have repeatedly called for longer-term, larger-scale research studies to clarify the roles that these factors play in the health of the aging brain."
"These are some of the first reports of this type in Alzheimer's, and that is encouraging, but it is not yet definitive evidence," Thies continued. "Longitudinal studies and clinical trials are expensive, and I'm deeply concerned that the trials we need will not happen because of the chronic underfunding of Alzheimer research by the federal government."
Framingham Study Shows Physical Activity Lowers Risk of Dementia, Especially in Men
Several long-term epidemiological studies have related physical activity and cognitive decline, dementia and/or Alzheimer's disease, although the results of published research studies thus far are not entirely consistent and several large studies failed to show an association. Most of these studies followed participants for less than six years or had significant loss to follow-up. Still needed are studies including long-term follow-up in older persons in age brackets at higher risk of incident Alzheimer's to elucidate the true relationship.
One such long-term trial is the Framingham Study, a population-based study that has followed participants residing in the town of Framingham, Massachusetts since 1948 for cardiovascular risk factors, and is now also tracking cognitive performance. Framingham is widely acknowledged as a premier longitudinal study; it has continued to yield valuable information for more than 40 years.
Zaldy Tan, MD, MPH, of Brigham and Women's Hospital, GRECC, VA Boston, and Harvard Medical School, and colleagues estimated the levels of 24-hour physical activity of more than 1,200 elderly participants from the Framingham Study (742 female; age 76 +\-5) during the study's 20th examination cycle (1986-87) and followed them for the development of dementia. They divided the participants into five groups based on level of physical activity, from lowest (Q1) to highest (Q5).
Over two decades of follow-up (mean 9.9 +/-5 years), 242 participants developed dementia (of which 193 were Alzheimer's). The researchers found that participants who performed moderate to heavy levels of physical activity had about a 40 percent lower risk of developing any type of dementia. Further, people who reported the lowest levels of physical activity were 45 percent more likely to develop any type of dementia compared to those who reported higher levels of activity. Similar results were seen when analyses were limited to Alzheimer's alone. Analyses showed that the observed associations were largely evident in men in the study.
"This is the first study to follow a large group of individuals for this long a period of time," Tan said. "It suggests that lowering the risk for dementia may be one additional benefit of maintaining at least moderate physical activity, even into the eighth decade of life."
Tea Consumption Slows Cognitive Decline in the Cardiovascular Health Study
Observational studies have shown associations between consumption of either tea or coffee and cognitive function in older adults, but data including long-term follow-up and rate of change in cognitive function are lacking.
Lenore Arab, PhD, of UCLA, and colleagues used data on more than 4,800 men and women aged 65 and older from the Cardiovascular Health Study to examine the relationship between consumption of tea, coffee, and change in cognitive function over time. Study participants were followed up for up to 14 years for naturally-occurring cognitive decline using the Mini-Mental State Examination (3MSE) administered at baseline and annually up to 8 times. People scored on the average 1.17 points less per year. Tea and coffee drinking were assessed using a food frequency questionnaire.
The researchers found that people who consumed tea at a variety of levels had significantly less cognitive decline (17-37 percent) than non-tea drinkers. More specifically, study participants who drank tea 5-10 times/year, 1-3 times/month, 1-4 times/week, and 5+ times/week had average annual rates of decline 17 percent, 32 percent, 37 percent, and 26 percent lower, respectively, than non-tea drinkers.
According to the scientists, coffee consumption did not show any effect except at the very highest level of consumption – where it was associated with significantly decreased decline of 20 percent.
"The suggestion of a positive effect of tea consumption in slowing cognitive decline requires further investigation," Arab said. "Interestingly, the observed associations are unlikely to be related to caffeine, which is present in coffee at levels 2-3 times higher than in tea."
Vitamin D Deficiency Increases Risk of Cognitive Impairment
Recent European studies suggest vitamin D deficiency is associated with increased odds of cognitive impairment and dementia in later life, although previous findings from the U.S. have been mixed. Interest in vitamin D has intensified recently as research has suggested that it may play a role in a variety of age-associated diseases.
David Llewellyn, PhD, of the University of Exeter Peninsula Medical School (UK), and colleagues examined information from 3,325 adults aged 65 years and older from the Third National Health and Nutrition Examination Survey (NHANES III), a study that was carefully designed to accurately represent the U.S. non-institutionalized population. Vitamin D levels were measured from blood samples and compared with performance on a measure of general cognitive function that incorporated tests of memory, orientation in time and space, and ability to maintain attention.